Hamilton Electronics EPHUM011 User Manual

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

pH ARC Sensors

Modbus RTU

Programmer’s Manual

Firmware version:

EPHUM011

624300/01 page 1 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Important Notice

All rights reserved. No part of this document may be reproduced, stored in a retrieval system, or
transmitted in any form without writtenpermission from HAMILTON Bonaduz AG.

The contents of this manual are subject to change without notice. Technical changesreserved.
All efforts have been made to ensure the accuracy of the contents of this manual. However, should any

errors be detected, HAMILTON Bonaduz AG would greatly appreciate being informed of them.
The above notwithstanding, HAMILTON Bonaduz AG can assume no responsibility for any errors in

this manual or their consequences.
Copyright © 2010 HAMILTON Bonaduz AG, Switzerland.

Rev. Revision Date Author Change Description
01 22.04.2010 Ph. Arquint

Initial Version 01 for EPHUM011
R. Dietrich
D. Schönfuss

624300/01 page 2 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Table of Content

1 MODBUS RTU GENERAL INFORMATION ............................................................................... 4

1.1 INTRODUCTION ..................................................................................................................... 4

2 PH ARC SENSOR COMMANDS IN MODBUS RTU................................................................... 5

2.1 GENERAL............................................................................................................................. 5

2.2 OPERATOR LEVELS AND PASSWORDS ..................................................................................... 5

2.2.1 Reading / Setting Operator Level................................................................................. 5

2.2.2 Changing Passwords for Operator Level ..................................................................... 6

2.3 CONFIGURATION OF THE SERIAL RS485 INTERFACE .................................................................7

2.3.1 Device Address........................................................................................................... 7

2.3.2 Baud Rate................................................................................................................... 8

2.4 CONFIGURATION OF THE ANALOG INTERFACES......................................................................... 9

2.4.1 Available Analog Interfaces......................................................................................... 9

2.4.2 Available Analog Interface Modes ............................................................................... 9

2.4.3 Description of the Analog Interfaces 1 and 2.............................................................. 10

2.4.4 Selection of an Analog Interface Mode...................................................................... 10

2.4.5 Configuration of the 4-20 mA Interface...................................................................... 11

2.4.6 Reading the Internally Measured Output Current....................................................... 17

2.5 MEASUREMENT................................................................................................................... 18

2.5.1 Definition of Measurement Channels and Physical Units ........................................... 18

2.5.2 Primary Measurement Channel 1 (pH) ...................................................................... 20

2.5.3 Primary Measurement Channel 6 (Temperature)....................................................... 22

2.5.4 Definition of the Measurement Status for PMC1 / PMC6............................................ 23

2.5.5 Secondary Measurement Channels 1-16................................................................... 24

2.6 CONFIGURATION OF THE MEASUREMENT ............................................................................... 26

2.6.1 Available Parameters................................................................................................ 26

2.6.2 PA9: Moving Average................................................................................................ 27

2.6.3 PA12: Moving Average R.......................................................................................... 30

2.7 CALIBRATION...................................................................................................................... 32

2.7.1 Available Calibration Points....................................................................................... 32

2.7.2 Definitions of Calibration Points................................................................................. 33

2.7.3 Calibration Procedure................................................................................................ 35

2.7.4 Reading the Calibration Status.................................................................................. 44

2.7.5 Currently active Calibration Parameters part 1........................................................... 48

2.7.6 Currently active Calibration Parameters part 2........................................................... 48

2.7.7 Currently active Calibration Parameters part 3........................................................... 49

2.7.8 Currently active Calibration Parameters part 4........................................................... 49

2.7.9 Special Commandsfor Calibration with VISICAL....................................................... 50

2.7.10 Calibration Standards................................................................................................ 51

2.8 SENSOR STATUS ................................................................................................................ 57

2.8.1 Temperature Ranges ................................................................................................ 57

2.8.2 Operating Hours and Counters.................................................................................. 58

2.8.3 Warnings .................................................................................................................. 59

2.8.4 Errors........................................................................................................................ 60

2.8.5 Reading Definition of SIP and CIP............................................................................. 62

2.8.6 Reading the Sensor’s Quality Indicator...................................................................... 63

2.9 SENSOR IDENTIFICATION AND INFORMATION........................................................................... 64

2.9.1 General Information .................................................................................................. 64

2.9.2 Sensor Identification.................................................................................................. 64

2.9.3 Free User Memory Space ......................................................................................... 65

2.10 SYSTEM COMMANDS ........................................................................................................... 66

2.10.1 Recall Sensor’s Factory Settings............................................................................... 66

3 ABBREVIATIONS.................................................................................................................... 66

624300/01 page 3 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

1 Modbus RTU general information

1.1 Introduction

This document describes in detail the pH ARC Sensors Modbus RTU interface. It is addressed to
software programmers.

The general information about Modbus command structures and its implementation in the HAMILTON
ARC Sensor family is described in detail in Chapter 1 of the

“VISIFERM DO Modbus RTU Programmer’s Manual”(p/n 624179/01).
If you need this general information about Modbus programming, then please consult p/n 624179/01.
In the present manual, only the specific command structure for the pH ARC Sensors is described. It is

valid for the firmware version:

EPHUM011
Please check the softwareversion by reading register 1032.
This present definition of the command structure is an additional document to the Operating

Instructions of the specific pH ARC Sensors. Before reading this manual, the operating instructions of
the sensors should be read and understood.

624300/01 page 4 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2 pH ARC Sensor Commands in Modbus RTU

2.1 General

In order to communicate with a pH ARC Sensor over ModbusRTU protocol a Modbus master terminal
application software is needed. The Modbus RTU is an open standard and a number of free and
commercial application toolkits are available.

This manual contains examples and illustrations from WinTECH Modbus Master ActiveX Control tool:
WinTECH (www.win-tech.com) “Modbus Master OCX for Visual Basic”. The Modbus Organisation
(www.modbus.org/tech.php) provides other links to a wide variety of Modbus terminal softwares.

In the present manual the addressing of the Modbus registers starts at 1. But the Modbus master
protocol operates with register addresses starting at 0. Usually, the Modbus master software translates
the addressing. Thus, the register address of 2090 will be translated by the Modbus master software to
2089 which is sent to the sensor (Modbus slave).

Attention:
When configuring and calibrating the sensor, please limit write operations to a reasonable number.
More than 100’000 write operations will physically damage the memory of the sensor.
Furthermore, for the Free User Memory Space (see chapter 2.9.3), the write operations are limited to
10’000.

2.2 Operator levels and Passwords

2.2.1 Reading / Setting Operator Level

A pH ARC Sensor can be operated in three different operator levels. Each operator level allowsa
defined access to a specific set of commands.

Abbreviation Description Code (hex) Password (decimal)
U User (lowest level) 0x03 0
A Administrator 0x0C 18111978
S Specialist 0x30 16021966

Figure 2.2.1.1: Definition of operator level and default passwords
At each power up or processor reset, the operator level falls back to the default level U.
The active operator level can be read and written in register 4288.

Start
register
4288 4 Operator Level Password 3, 4, 16 U/A/S U/A/S

Figure 2.2.1.2: Definition of register 4288.

Command: Active operator level
Parameter: Operator level Password
Format: hex decimal
Value:

Figure 2.2.1.3: Example to read the active operator level (function code 3, start register address 4288,

Number of
registers

0x03 0

number of registers 4): The active operator level is 0x03 (User). The sensor does not report the
password. The value 0 is returned instead.

Reg1 / Reg2 Reg3 / Reg4 Modbus

function code

Modbus address: 4288 Length: 4 Type: 3

Read
access

Write
access

Read

624300/01 page 5 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Command: Operator level
Parameter: Operator level Password
Format: Hex decimal
Value:

Figure 2.2.1.4: Example to read the active operator level: the active level is 0x30 (Specialist). The

sensor does not report the password. The value 0 is returned instead.

Command: Operator level
Parameter: Operator level Password
Format: Hex decimal
Value:

Figure 2.2.1.5: Example to set the operator level to 0x03 (User). The password 0 has to be sent.

Command: Operator level
Parameter: Operator level Password
Format: Hex decimal
Value:

Figure 2.2.1.6: Example to set the active operator level to 0xC (Administrator). The correct password

has to be sent.

Command: Operator level
Parameter: Operator level Password
Format: Hex decimal
Value:

Figure 2.2.1.7: Example for a Modbus error. If the level or the password is not correct, (Operator level =

0x0B), the sensor answers with a Modbus error message “Slave device exception response”
(see chapter 1.6).

0x30 0

0x03 0

0x0C 18111978

0x0B 18111978

Modbus address: 4288 Length: 4 Type: 3

Modbus address: 4288 Length: 4 Type: 16

Modbus address: 4288 Length: 4 Type: 16

Modbus address: 4288 Length: 4 Type: 16

Read

Write

Write

Write

2.2.2 Changing Passwords for Operator Level

The passwordsfor accessing the operator levels A and S can be modified by S (Specialist) only. U
(User) and A (Administrator) have no right to change any password. The new password will remain
stored after power down.

Start
register
4292 4 Level New password 16 None S

Figure 2.2.2.1: Definition of register 4292.

Command: Password
Parameter: Operator level Pass number
Format: Hex Decimal
Value:

Figure 2.2.2.2: Example to set the Password of operator level S (code 0x30) to 12345678.

Number of
registers

0x30 12345678

Reg1 / Reg2 Reg3 / Reg4 Modbus

Read

function code

Modbus address: 4292 Length: 4 Type: 16

access

Write
access

Write

624300/01 page 6 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.3 Configuration of the serial RS485 Interface

Factory settings of the RS485:
Parity is none, 1 start bit, 8 data bits, 2 stop bits (in total: 11 bits).

2.3.1 Device Address

2.3.1.1 Reading and Writing the Device Address

The sensor specific device address can be read and written in register 4096.

Start

register

4096 2 device address 3, 4, 16 U/A/S S

Figure 2.3.1.1.1: Definition of register 4096.

Command: Com address
Parameter: Modbus address
Format: Decimal
Value:

Figure 2.3.1.1.2: Example to read the device address.
The device address can be set by S (Specialist), defaultvalue is 1.

Command: Com address
Parameter: Modbus address
Format: Decimal
Value:

Figure 2.3.1.1.3: Example to set the device address to 3.

2.3.1.2 Reading the Device Address Limits

The device address limits can be read in register 4098.

Number of
registers

1

3

Reg1 / Reg2 Modbus

function code

Modbus address: 4096 Length: 2 Type: 3

Modbus address: 4096 Length: 2 Type: 16

Read
access

Write
access

Read

Write

Start
register
4098 4 Min. device

Figure 2.3.1.2.1: Definition of register 4098.

Command: Com address limits
Parameter: Min value Max value
Format: Decimal Decimal
Value:

Figure 2.3.1.2.2: Example to read the device addresslimits: Min = 1, Max = 32.

624300/01 page 7 / 67

Number of
registers

1 32

Reg1 / Reg2 Reg3 / Reg4 Modbus

address

function code
Max. device
address

Modbus address: 4098 Length: 4 Type: 3

3, 4 U/A/S none

Read
access

Write
access

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.3.2 Baud Rate

2.3.2.1 Reading and Writing the Baud Rate

The baud rate can be read and written in register 4102.

Start
register

4102 2 Baud rate code
Figure 2.3.2.1.1: Definition of register 4102.
The code for the baud rate is defined as follows:

Baud rate 4800 9600 19200 38400 57600 115200

Code 2 3 4 5 6 7
Figure 2.3.2.1.2: Code for the baud rates.

Command: Com baud rate

Parameter: Baud rate code

Format: Decimal

Value:
Figure 2.3.2.1.3: Example to read the baud rate code,4 corresponds 19200 baud.

The baud rate can be set by S (Specialist), default is 19200.

Command: Com baud rate

Parameter: Baud rate code

Format: Decimal

Value:
Figure 2.3.2.1.4: Example to set the baud rate to 38400 baud with code 5.

Number of
registers

4

5

Reg1 / Reg2 Modbus

function code
3, 4, 16 U/A/S S

(definition see below)

Modbus address: 4102 Length: 2 Type: 3

Modbus address: 4102 Length: 2 Type: 16

Read
access

Write
access

Read

Write

2.3.2.2 Reading the Baud Rate Limits

The baud rate limits can be read in register 4104.

Start

register

4104 4 Min. Baud rate
Figure 2.3.2.2.1: Definition of register 4104.

Command: Com baud limits

Parameter: Min Baud rate code Max Baud rate code

Format: Decimal Decimal

Value:
Figure 2.3.2.2.2: Example to read the baud rate code limits: Min = 2, Max = 7 (see Figure 2.3.2.1.2).

Number of
registers

2 7

Reg1 / Reg2 Reg3 / Reg4 Modbus

code

Read

function code
Max. Baud rate
code

Modbus address: 4104 Length: 4 Type: 3

3, 4 U/A/S none

access

Write
access

Read

624300/01 page 8 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4 Configuration of the Analog Interfaces

2.4.1 Available Analog Interfaces

A pH ARC Sensor has two individual physical analog interfaces that have identical functionalities, but
can be configured independently from each other.

 Analog Output Interface 1 (AO1)
 Analog Output Interface 2 (AO2)

The number of analog interfaces is defined in register 4320.

Start
register
4320 2 Available analog interfaces 3, 4 U/A/S none

Figure 2.4.1.1: Definition of register 4320.

Command: Avail analog interfaces
Parameter: Available analog

Format: Hex
Value:

Figure 2.4.1.2: Example to read the available analog interfaces. The answer is “0x03”meaning that

Number of
registers

interfaces

0x03

there exists an Analog Interface 1 (AO1) and an Analog Interface 2 (AO2).

Reg1 / Reg2 Modbus

function code

Modbus address: 4320 Length: 2 Type: 3

Read
access

Write
access

Read

2.4.2 Available Analog Interface Modes

With register 4322, the available analog interface modes for AO1 and AO2 are defined

Start
register

4322 8 Available

Figure 2.4.2.1: Definition of register 4322. It defines the analog interface modes available for AO1 and

Number of
registers

AO2. The analog interface modes are described in Figure 2.4.2.2.

Reg1 /
Reg2

Analog
Interface
Modes for
AO1

Reg3 /
Reg4

Available
Analog
Interface
Modes
for AO2

Reg5 /
Reg6

reserved reserved 3,4 U/A/S none

Reg7 /
Reg8

Modbus
function
code

Read
access

Write
access

Code
(Hex)
0x00 4-20 mA inactive Analog interface deactivated
0x01 4-20 mA fixed Set to a constant output value for current loop testing
0x02 4-20 mA linear Linear output of measurement (PMC1 / 6)
0x04 4-20 mA bilinear Bilinear output of measurement (PMC1 / 6)

Figure 2.4.2.2: Definition of the analog interface modes, valid for both AO1 and AO2.

Command: Analog Interface Modes
Parameter: Available Analog

Format: Hex Hex Hex Hex
Value:

Figure 2.4.2.3: Example to read register 4322: all modes defined in figure 2.4.2.2 are available for both

624300/01 page 9 / 67

Analog Interface
Mode

Interface Modes for
AO1

0x07 0x07 0x0 0x0

AO1 and AO2.

Description

Modbus address: 4322 Length: 8 Type: 3
Available Analog
Interface Modes for
AO2

reserved reserved

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4.3 Description of the Analog Interfaces 1 and 2

Register 4352 / 4480 contain the descriptions of AO1 / AO2 as plain text ASCII:

Start
register
4352 8 Description of AO1 3, 4 U/A/S none
4480 8 Description of AO2 3, 4 U/A/S none

Figure 2.4.2.1: Definition of register 4352 and 4480

Command: Current interface text
Parameter: Text
Format: Character
Value:

Figure 2.4.2.2: Example to read the description of AO1. The text is “mA interface #1”. Accordingly,

Command: Current interface text
Parameter: Text
Format: Character
Value:

Figure 2.4.2.3: Example to read the description of AO2. The text is “mA interface #2”. Accordingly,

 pH ARC Sensors do not have an ECS (in contrast to VISIFERM DO)!
 Data structure: register address offset between AO1 and AO2 is always 128.

Number of
registers

mA interface #1

AO1 is physically configured as a 4-20 mA current output.

mA interface #2

AO2 is physically configured as a 4-20 mA current output.

Attention:

Reg1 … Reg8
16 ASCII characters

Modbus address: 4352 Length: 8 Type: 3

Modbus address: 4480 Length: 8 Type: 3

Modbus
function code

Read
access

Write
access

Read

Read

2.4.4 Selection of an Analog Interface Mode

The analog interface mode of AO1 / AO2 is selected by programming the analog interface mode in
register 4360 / 4488.

Start
register
4360 2 Active analog interface mode for AO1 3, 4, 16 U/A/S S
4488 2 Active analog interface mode for AO2 3, 4, 16 U/A/S S

Figure 2.4.4.1: Definition of register 4360 / 4488. Only one bit can be set.

Command: Active interface mode
Parameter: Mode
Format: Hex
Value:

Figure 2.4.4.2: Example to set the analog interface mode of AO1 to 0x02 (4-20 mA linear output).

Number of
registers

0x02

Reg1 / Reg2 Modbus

function code

Modbus address: 4360 Length: 2 Type: 16

Read
access

Write
access

Write

624300/01 page 10 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4.5 Configuration of the 4-20 mA Interface

Note:
The configuration of AO1 / AO2 is only effective if register 4360 / 4488 (active analog interface mode) is
set to the value 0x01, 0x02 or 0x04.

2.4.5.1 Reading the Available Primary Measurement Channels to be Mapped to the Analog
Output

Start
register
4362 2 Available Primary Measurement Channels

4490 2 Available Primary Measurement Channels
Figure 2.4.5.1.1: Definition of register 4362 / 4490.
For the definition of the Primary Measurement Channels(PMC), see chapter 2.5.

Code

(Hex)

0x01 PMC1 (pH)

0x20 PMC6 (temperature)
Figure 2.4.5.1.2: Code for selection of the primary measurement channel.

Command: Available PMC AO1

Parameter: Available PMC 20 mA

Format: hex

Value:
Figure 2.4.5.1.3: Example to read the available Primary Measurement Channels (PMC) for AO1. The

Number of
registers

Primary Measurement Channel (PMC)

not available

0x21

hexadecimal value of “0x21”defines that PMC1 (pH) or PMC6 (temperature) can be mapped to
AO1. Register 4490 contains the same value “0x21”. Accordingly, PMC1 or PMC6 can be
mapped to AO2 as well.

Reg1 / Reg2 Modbus

function code
3, 4 U/A/S none

for AO1

3, 4 U/A/S none

for AO2

Modbus address: 4362 Length: 2 Type: 3

Read
access

Write
access

Read

2.4.5.2 Selecting the Primary Measurement Channel to be Mapped to the Analog Interface

Start

register

4364 2 SelectedPMC for AO1 3, 4, 16 U/A/S S

4492 2 SelectedPMC for AO2 3, 4, 16 U/A/S S
Figure 2.4.5.2.1: Definition of register 4364 / 4492. Only one bit can be set.

Command: Active PMC AO1

Parameter: Current PMC 20mA

Format: hex

Value:
Figure 2.4.5.2.2: Example to read the current primary measurement channel mapped to AO1, defined

624300/01 page 11 / 67

Number of
registers

0x01

in register 4364. The value “0x01”is returned, saying that PMC1 is mapped to AO1 (factory
setting).

The factory setting for register 4492 is “0x20”, mapping PMC6 to AO2.

Reg1 / Reg2 Modbus

function code

Modbus address: 4364 Length: 2 Type: 3

Read
access

Write
access

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4.5.3 Reading the Minimum and Maximum Possible Physical Output Current

Start
register
4366 4 Min physical

4494 4 Min physical

Figure 2.4.5.3.1: Definition of register 4366 / 4494

Command: Limits AO1
Parameter: Min limit [mA] Max limit [mA]
Format: Float Float
Value:

Figure 2.4.5.3.2: Example to read the min and max output current of AO1. Min is fixed to 3.5 and Max

2.4.5.4 Reading the Minimum, Maximum and Mid Current for Measurement Value Output

Start
register

4370 6 Min output for

4498 6 Min output for

Figure 2.4.5.4.1: Definition of register 4370 / 4498

Number of
registers

3.5 22

is fixed to 22 mA (Currents above 20 and below 4 mA indicate erroneous measurements or
errors).
The same values are stored in register 4494 for AO2.

Number of
registers

Reg1 / Reg2 Reg3 / Reg4 Modbus

function code

Max physical
output current
for AO1 [mA]

output current
for AO2 [mA]

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

measurement
value for AO1
[mA]

measurement
value for AO2
[mA]

output current

for AO1 [mA]

Max physical

output current

for AO2 [mA]

Modbus address: 4366 Length: 4 Type: 3

Max output for
measurement
values for AO1
[mA]

Max output for
measurement
values for AO2
[mA]

3, 4 U/A/S none

3, 4 U/A/S none

Mid output
(bilinear) for
measurement
values for
AO1 [mA]
Mid output
(bilinear) for
measurement
values for
AO2 [mA]

Read
access

function
code
3, 4 U/A/S none

3, 4 U/A/S none

Write
access

Read
access

Read

Write
access

Command: MinMaxMid current AO1
Parameter: Min current [mA] Max current [mA] Mid current [mA]
Format: Float Float Float
Value:

Figure 2.4.5.4.2: Example to read the min, max and mid output current for measurement values for

AO1. They are fixed to 4, 20 and 12 mA.

The same values are stored in register 4498 for AO2.

Note:
Mid current must alwaysbe defined. However, in linear output mode, the mid current value has no
physical meaning and will not affect the 4-20 mA output.

624300/01 page 12 / 67

4 20 12

Modbus address: 4370 Length: 6 Type: 3

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4.5.5 Reading the Selected Physical Unit for Analog Interface

Start
register
4376 2 Selected physical unit of AO1

4504 2 Selected physical unit of AO2

Figure 2.4.5.5.1: Definition of register 4376 / 4504.

Command: Avail unit AO1
Parameter: Available unit
Format: Hex
Value:

Figure 2.4.5.5.2: Example to read the selected unit of the selected PMC of AO1. The value returned is

2.4.5.6 Defining the Measurement Values for 4, 12 and 20 mA Output

Start
register

4378 6 Measurement

4506 6 Measurement

Figure 2.4.5.6.1: Definition of register 4378 / 4506.

Number of
registers

0x001000

“0x001000”, accordingly, the unit is pH. The physical unit for PMC is defined in Reg. 2090 or
2410 and applies automatically for 4-20 mA output.

Number of
registers

Reg1 / Reg2 Modbus

function code
3, 4 U/A/S none

(see chapter 2.5.1)

3, 4 U/A/S none

(see chapter 2.5.1)

Modbus address: 4376 Length: 2 Type: 3

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

function
code

value at
Min Output
Current (4 mA)
for AO1

value at
Min Output
Current (4 mA)
for AO2

Measurement
value at
Max Output
Current (20
mA) for AO1
Measurement
value at
Max Output
Current (20
mA) for AO2

Measurement
value at
Mid Output
Current (12
mA) for AO1
Measurement
value at
Mid Output
Current (12
mA) for AO2

3, 4, 16 U/A/S S

3, 4, 16 U/A/S S

Read
access

Read
access

Write
access

Read

Write
access

Command: MinMaxMid value AO1
Parameter: Min value Max value Mid value
Format: Float Float Float
Value:

Figure 2.4.5.6.2: Example to set the min value to 3 (for 4 mA), the max value to 10 (for 20 mA) and the

mid value to 7 (for 12 mA). The corresponding physical unit can be read in register 4376 / 4504
and in 2090 / 2410.

Note:
Mid current must alwaysbe defined. However, in linear output mode, the mid current value has no
physical meaning and will not affect the 4-20 mA output.

624300/01 page 13 / 67

3 10 7

Modbus address: 4378 Length: 6 Type: 16

Write

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

pH ARC sensor: 4-20mA interface - linear

35
30
25
20
15
10

5

temperature [°C]

0

0 4 8 12 16 20 24

-5

-10

-15

Temp [°C]
pH

Curre nt [mA]

Figure 2.4.5.6.3: Example of linear 4-20 mA output characteristicsfor pH or temperature.

Current pH Temperature
4 mA 2 -10 °C
20 mA 9 +30 °C

11
10
9
8
7
6
5
4
3
2
1

pH

pH ARC sensor: 4-20mA interface - bilinear

35
30
25

Temp [°C]

20

pH

15
10

5

temperature [°C]

0

0 4 8 12 16 20 24

-5

-10

-15

Current [mA]

Figure 2.4.5.6.4: Example of bilinear 4-20 mA output characteristics for pH or temperature.

Current pH Temperature
4 mA 2 -10 °C
12 mA 9 +20 °C
20 mA 10 +30 °C

11
10
9
8
7
6
5
4
3
2
1

pH

624300/01 page 14 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Attention:
When assigning measurement values to 4-20 mA analog output by using register 4378 / 4506, you
need to consider the following:

 The PMC you have mapped to AO1 / AO2 (register 4364 / 4492)
 The physical unit currently in use for the selected PMC (register 2090 for PMC1 (pH) and

register 2410 for PMC6 (temperature).
Therefore, when the operator redefines one of the register 4364 / 4492, 2090 / 2410, the definitions of
the register 4378 / 4506 should be reviewed. If not, the current output at the 4-20 mA interfaces may be
wrong.

Note:
The physical unit of the analog output correspondsalways to the unit that is set for the selected PMC
(register 2090 for PMC1 or register 2410 for PMC6). Accordingly, not only the pH value is selectable at
the 4-20 mA interface, but also mV values, degrees centigrade or Kelvin.

Example:
Register 4364 is set to 1 (PMC1 is mapped to AO1).
Register 2090 is set to 0x1000 (the unit “pH”is assigned to PMC1).
Register 4378 is set to 2 and 10 (4 mA = pH 2, 20 mA = pH 10).
The sensor reads currently pH 4, the output at the 4-20 mA is accordingly 8 mA.
The operator now re-assigns register 2090 to the value of 0x200000 (unit = mV), but does not modify
all other registers. The sensor is still at pH 4 and reads now +170 mV. At the analog output, as 20 mA
is programmed to a value of 10 by register 4378, the current will go to the maximum value of 20 mA.
This will generate an interface warning “4-20 mA current set point not met”.

2.4.5.7 Defining a Constant Current Output for Testing

Note:
For constant current output, the AO1 / AO2 must be set to analog interface mode 0x01:

Start
register
4384 2 Constant current output value for

4512 2 Constant current output value for

Figure 2.4.5.7.1: Definition of register 4384 / 4512.

Command: Fixed value AO1
Parameter: Fixed value [mA]
Format: Float
Value:

Figure 2.4.5.7.2: Example to read the constant current output in mode 0x01 for AO1. It is set to 10 mA.

Number of
registers

10

Reg1 / Reg2 Modbus

function code
3, 4, 16 U/A/S S

AO1 [mA]

3, 4, 16 U/A/S S

AO2 [mA]

Modbus address: 4384 Length: 2 Type: 3

Read
access

Write
access

Read

624300/01 page 15 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4.5.8 Defining the Error and Warning Output of the 4-20 mA Interface

Errors and warnings can be mapped to the AO1 / AO2.

Start
register

4386 8 Code of

4514 8 Code of

Figure 2.4.5.8.1: Definition of register 4386 / 4514.

Bit # Code (hex) Behaviour of the 4-20 mA interface in case of errors and warnings
0 (LSB) 0x000001 Error continuous output

16 0x010000 Warning continuous output

Figure 2.4.5.8.2: Code for the 4-20 mA interface in case of errors and warnings.

Number of
registers

Reg1 /
Reg2

warnings
and errors
(see Figure

2.4.4.8.2)
for AO1

warnings
and errors
(see Figure

2.4.4.8.2)
for AO2

not available
not available

Reg3 /
Reg4

Current
in case of
“warning”
[mA]
for AO1

Current
in case of
“warning”
[mA]
for AO2

Reg5 /
Reg6

Current
in case of
“error”
[mA]
for AO1

Current
in case of
“error”
[mA]
for AO2

Reg7 /
Reg8

Current in
case of
“T exceed”
[mA]
for AO1

Current in
case of
“T exceed”
[mA]
for AO2

Modbus
function
code
3, 4, 16 U/A/S S

3, 4, 16 U/A/S S

Read
access

Write
access

If the corresponding bits for the errors and warnings are not set (=0x00), the respective options are
inactive.

The default settings are:

 Code 0x01
 current in case of warnings: 3.5 mA
 current in case of errors: 3.5 mA
 current in case of temperature exceed: 3.5 mA

Command: ErrorWarnings AO1
Parameter: Warning code Current in case of

Format: Hex Float Float Float
Value:

Figure 2.4.5.8.4: Example: Read the settings for AO1 in case of warnings and errors. Warning code

0x010001 corresponds to the continuous output current in case of warning (0x010000) and
continuous output current in case of error (0x01) of 3.5 mA. The output current in case of
temperature exceed is 3.5 mA.

0x010001 3.5 3.5 3.5

Modbus address: 4386 Length: 8 Type: 3

Current in case of
warning
[mA]

error

[mA]

Read
Current in case of
temperature exceed
[mA]

624300/01 page 16 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.4.6 Reading the Internally Measured Output Current

Reg. 4414 / 4542 provides internal parameters of AO1 / AO2:

 the setpoint to which the current is regulated in a closed loop control
 the electrical current the sensor is measuring to feed the closed loop control

These values are helpful in order to compare against the externally measured electrical current.

Start
register
4414 4 Set point

4542 4 Set point

Figure 2.4.6.1: Definition of register 4414 / 4542.

Command: Internal values AO1
Parameter: Set point

Format: Float Float
Value:

Figure 2.4.6.2: Example to read the internal values of AO1, depending on the analog interface mode.

Number of
registers

[mA]

9.99186 9.99742

Reg1 / Reg2 Reg3 / Reg4 Modbus

[mA]
AO1

[mA]
AO2

function code
Internally measured
[mA]
AO1
Internally measured
[mA]
AO2

Modbus address: 4414 Length: 4 Type: 3
Internally measured
[mA]

3, 4 U/A/S none

3, 4 U/A/S none

Read
access

Write
access

Read

624300/01 page 17 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5 Measurement

2.5.1 Definition of Measurement Channels and Physical Units

The pH ARC Sensor Modbus register structure allows the definition of 6 individual Primary
Measurement Channels (PMC), and 16 individual Secondary Measurement Channels (SMC).

Bit # Hex code Description Definition

0 (LSB) 0x000001 PMC1 pH

1 0x000002 PMC2 not available

not available

4 0x000010 PMC5 not available

5 0x000020 PMC6 Temperature
6 0x000040 SMC1 R glass
7 0x000080 SMC2 R reference
8 0x000100 SMC3 R auxiliary
9 0x000200 SMC4 E pH vs. ref
10 0x000400 SMC5 E SG vs. ref
11 0x000800 SMC6 E aux vs. ref
12 0x001000 SMC7 E reference
13 0x002000 SMC8 pH act
14 0x004000 SMC9 T act

15 0x008000 SMC10 not available

…

21 (MSB) 0x200000 SMC16 not available

Figure 2.5.1.1: full list of PMC1 to 6 and SMC1 to 16.
In Register 2048, the available PMC and SMC are defined for a specific pH ARC Sensors and a

specific operator level.

Start
register
2048 2 Available measurement channels

Figure 2.5.1.2: Definition of register 2048.

Command: Avail. PMC and SMC
Parameter: Avail. PMC and

Format: Hex
Value: 0x06E1

Figure 2.5.1.3: Example to read Reg. 2048 for Polilyte Plus ARC.

Number of
registers

SMC

In case of operator A/U, the value 0x06E1 is returned. In other words the following PMC and
SMC are available to A/U: PMC1 / PMC6 / SMC1 / SMC2 / SMC4 / SMC5
In case of operator S, the value 0x066E1 is returned. In other words the following PMC and SMC
are available to S: PMC1 / PMC6 / SMC1 / SMC2 / SMC4 / SMC5 / SMC8 / SMC9

Reg1 / Reg2 Modbus

function code
3, 4 U/A/S none

PMC and SMC (bitwise set)

Modbus address: 2048 Length: 2 Type: 3

Read
access

Write
access

Read

624300/01 page 18 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

The pH ARC Sensor register structure uses the following physical units used for Primary or Secondary
Measurement Channels.

Bit # Hex code Physical unit Start register. (8 ASCII characters, length 4 registers,

Type 3, read for U/A/S)
0 (LSB) 0x00000001 none 1920
1 0x00000002 K 1924
2 0x00000004 °C 1928
3 0x00000008 °F 1932
4 0x00000010 %-vol 1936
5 0x00000020 %-sat 1940
6 0x00000040 ug/l ppb 1944
7 0x00000080 mg/l ppm 1948
8 0x00000100 g/l 1952
9 0x00000200 uS/cm 1956
10 0x00000400 mS/cm 1960
11 0x00000800 1/cm 1964
12 0x00001000 pH 1968
13 0x00002000 mV/pH 1972
14 0x00004000 kOhm 1976
15 0x00008000 MOhm 1980
16 0x00010000 pA 1984
17 0x00020000 nA 1988
18 0x00040000 uA 1992
19 0x00080000 mA 1996
20 0x00100000 uV 2000
21 0x00200000 mV 2004
22 0x00400000 V 2008
23 0x00800000 mbar 2012
24 0x01000000 Pa 2016
25 0x02000000 Ohm 2020
26 0x04000000 %/°C 2024
27 0x08000000 ° 2028
28 0x10000000 not used 2032
29 0x20000000 not used 2036
30 0x40000000 not used 2040
31 (MSB) 0x80000000 SPECIAL 2044

Figure 2.5.1.4: Definition of physical units used for PMC and SMC.

Command: Unit text
Parameter: Text
Format: Character
Value:

Figure 2.5.1.5: Example to read the physical unit in plain text ASCII in register 1968

624300/01 page 19 / 67

pH

Modbus address: 1968 Length: 4 Type: 3

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.2 Primary Measurement Channel 1 (pH)

2.5.2.1 Description of PMC1

In register 2080, a plain text ASCII description of PMC1 is given.

Start
register
2080 8 Description of PMC1 3, 4 U/A/S none

Figure 2.5.2.1.1: Definition of register 2080.

Command: PMC 1 text
Parameter: Text
Format: Character
Value:

Figure 2.5.2.1.2: Example to read the description. It is “pH”.

2.5.2.2 Selecting the Physical Unit for PMC1

In register 2088, the available physical units for this channel are defined.

Start
register
2088 2 Available physical units of PMC1 3, 4 U/A/S none

Figure 2.5.2.2.1: Definition of register 2088.

Command: PMC1 available units
Parameter: Units
Format: Hex
Value:

Figure 2.5.2.2.2: Example to read the available physical units of PMC1: pH (0x001000) + mV

Number of
registers

pH

Number of
registers

0x201000

(0x200000), total 0x201000.

Reg1 … Reg8
16 ASCII characters

Reg1 / Reg2
(bitwise defined)

Modbus
function code

Modbus address: 2080 Length: 8 Type: 3

Modbus
function code

Modbus address: 2088 Length: 2 Type: 3

Read
access

Read
access

Write
access

Write
access

Read

Read

In register 2090, the active physical unit for this channel can be selected, by choosing one of the
physical units that are defined in register 2088.

Start
register
2090 2 Selected active physical unit for the

Figure 2.5.2.2.3: Definition of register 2090. Only one bit can be set.

Command: PMC1 set unit
Parameter: Unit
Format: Hex
Value:

Figure 2.5.2.2.4: Example to set the physical unit of PMC1 to pH (0x1000).

Changing the physical unit has also an influence on the output of AO1 / AO2, as the same physical unit
is active for the analog outputs. All limits of the 4-20 mA analog output have to be redefined after
changing the physical unit!

Number of
registers

0x1000

Attention:

Reg1 / Reg2
(bitwise defined)

PMC1

Modbus
function code
16 none S

Modbus address: 2090 Length: 2 Type: 16

Read
access

Write
access

Write

624300/01 page 20 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.2.3 Reading the measurement value of PMC1

Register 2090 is also used to read the measurement values of PMC1.

Start
reg.

2090 10 Selected

Figure 2.5.2.3.1: Definition of register 2090. Measurement value of PMC1.

Command: PMC1 read

Num­ber of
reg.

(1)

Value is alwaysin the physical unit defined in register 2090.

(2)

Definition of the status see chapter 2.5.4. All bits set to zero means: no problem.

Reg1 /
Reg2

physical
unit

Reg3 /
Reg4

Measure

-ment
value of
PMC1

(1)

Reg5 /
Reg6

Measure

-ment

(2)

status

Reg7 /
Reg8

Min
allowed
value

(1)

Reg9 /
Reg10

Max
allowed
value

Modbus
function
code
3, 4 U/A/S none

(1)

Modbus address: 2090 Length: 10 Type: 3

Read
access

Parameter: Unit Value Status Min limit Max limit
Format: Hex Float Hex Float Float
Value:

0x1000 4.02503 0x00 0 14

Figure 2.5.2.3.2: Example to read register 2090. Physical unit is set to pH (0x1000), PMC1 is pH

4.02503, Status is 0x00, Min allowed value is pH 0, Max allowed value is pH 14.

Command: PMC1 read

Modbus address: 2090 Length: 10 Type: 3
Parameter: Unit Value Status Min limit Max limit
Format: Hex Float Hex Float Float
Value:

0x200000 175.9922 0x00 0 954.6541

Figure 2.5.2.3.3: Example to read register 2090. Physical unit is set to mV (0x200000), PMC1 is

175.9922 mV, Status is 0x00, Min allowed value is -414.0028 mV, Max allowed value is

414.0028 mV.

Write
access

Read

Read

For the definition of the measurement status see chapter 2.5.4.

Attention:
You cannot read selectively the registers 3 and 4 for the measurement value only. You have to read the
entire length of the command (10 registers) and extract the desired information.

624300/01 page 21 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.3 Primary Measurement Channel 6 (Temperature)

2.5.3.1 Description of PMC6

In register 2400, a plain text ASCII description of PMC6 is given

Start
register
2400 8 Description of PMC6 3, 4 U/A/S none

Figure 2.5.3.1.1: Definition of register 2400.

Command: PMC6 text
Parameter: Text
Format: Character
Value:

Figure 2.5.3.1.2: Example to read the description. It is “T”(Temperature).

2.5.3.2 Selecting the Physical Unit for PMC6

In register 2408, the available physical units of PMC6 are defined.

Start
register
2408 2 Available physical units of PMC6 3, 4 U/A/S none

Figure 2.5.3.2.1: Definition of register 2408.

Command: PMC6 available units
Parameter: Units
Format: Hex
Value:

Figure 2.5.3.2.2: Example to read the available physical unit for PMC6. K (0x02) + °C (0x04), total

0x06.

Number of
registers

T

Number of
registers

0x06

Reg1 … Reg8
16 ASCII characters

Modbus address: 2400 Length: 8 Type: 3

Reg1 / Reg2
(bitwise defined)

Modbus address: 2408 Length: 2 Type: 3

Modbus
function code

Modbus
function code

Read
access

Read
access

Write
access

Write
access

Read

Read

In register 2410, the active physical unit of PMC6 can be selected, by choosing one of the physical
units that are defined in register 2408.

Start
register
2410 2 Selected active physical unit of PMC6 16 none U/A/S

Figure 2.5.3.2.3: Definition of register 2410. Only one bit can be set.

Command: PMC6 set unit
Parameter: Unit
Format: Hex
Value:

Figure 2.5.3.2.4: Example to set the physical unit of PMC6 to °C (0x04).

Changing the physical unit has also an influence on the output of AO1 / AO2, as the same physical unit
is active for the analog outputs. All limits of the 4-20 mA analog output have to be redefined after
changing the physical unit!

Number of
registers

0x04

Attention:

Reg1 / Reg2
(bitwise defined)

Modbus
function code

Modbus address: 2410 Length: 2 Type: 16

Read
access

Write
access

Write

624300/01 page 22 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.3.3 Reading the measurement value of PMC6

Register 2410 is also used to read the measurement values of PMC6.

Start
reg.

2410 10 Selected

Figure 2.5.3.3.1: Definition of register 2410. Measurement value of PMC6.

Command: PMC6 read

Num­ber of
reg.

(1)

Value is alwaysin the physical unit defined in register 2410.

(2)

For definition of the status see chapter 2.5.4. All bits set to zero means: no problem.

Reg1 /
Reg2

physical
unit

Reg3 /
Reg4

Measure

-ment
value of
PMC6

(1)

Reg5 /
Reg6

Measure

-ment

(2)

status

Reg7 /
Reg8

Min
allowed
value

(1)

Reg9 /
Reg10

Max
allowed
value

Modbus
function
code
3, 4 U/A/S none

(1)

Modbus address: 2410 Length: 10 Type: 3

Read
access

Write
access

Read
Parameter: Unit Value Status Min limit Max limit
Format: Hex Float Hex Float Float
Value:

0x04 24.35834 0x00 -20 130

Figure 2.5.3.3.2: Example to read register 2410. Physical unit is set to °C (0x04), PMC6 is 24.35834

°C, Status is 0x00, Min allowed value is -20 °C, Max allowed value is 130 °C.

For definition of the measurement status see chapter 2.5.4.

Attention:
You cannot read selectively the registers 3 and 4 for the measurement value only. You have to read the
entire length of the command (10 registers) and extract the desired information.

2.5.3.4 Input of an Externally Measured Temperature

Unlike to the VISIFERM DO, this feature is not available for pH ARC Sensors.

2.5.4 Definition of the Measurement Status for PMC1 / PMC6

This is the definition of the status registers read in registers 2090 (PMC1) and 2410 (PMC6):

Bit # Hex code Description
0 (LSB) 0x01 Temperature out of measurement range (see chapter 2.8.1)
1 0x02 Temperature out of operating range (see chapter 2.8.1)
2 0x04 Calibration status not zero (see chapter 2.7.4)
3 0x08 Warning not zero (see chapter 2.8.3)
4 0x10 Error not zero (see chapter 2.8.4)

Figure 2.5.4.1: Definition of measurement status for Primary Measurement Channels.

624300/01 page 23 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.5 Secondary Measurement Channels 1-16

pH ARC Sensors do allow access to secondary measurement values (16 in total). The access to the
individual SMC depends on the operator level. The available SMC are defined in register 2048
according to the selected operator level and the sensor type (see chapter 2.5.1).

2.5.5.1 Description of SMC

The registers defined here give a plain text ASCII description of each available SMC.

Start
register
Address 8 Description of each SMC 3, 4 U/A/S none

Figure 2.5.5.1.1: Definition of registers at Address

Description Address Plain Text
SMC1 2464 R glass Resistance of the pH glass
SMC2 2496 R reference Resistance of the reference electrode
SMC3 2528 R auxiliary Resistance of the auxiliary electrode
SMC4 2560 E pH vs. ref Electrical potential between glass and reference electrode
SMC5 2592 E SG vs. ref Electrical potential between solution ground and reference
SMC6 2624 E aux vs. ref Electrical potential between auxiliary electrode and reference
SMC7 2656 E reference Electrical potential between reference electrode and electrical
SMC8 2688 pH act Current pH value (3-seconds-reading)
SMC9 2720 T act Current T value (3-seconds-reading)

Number of
registers

Reg1 … Reg8
16 ASCII characters

Description

(16 ASCII)

electrode
electrode
ground

Modbus
function code

Read
access

Write
access

Figure 2.5.5.1.2: Full list of starting register addresses for the plain text ASCII description of each SMC
Example:

Command: SMC 1 text
Parameter: Text
Format: Character
Value:

Figure 2.5.5.1.3: Example to read the description of SMC1 at address 2464. It is “R glass”.

624300/01 page 24 / 67

R glass

Modbus address: 2464 Length: 8 Type: 3

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.5.5.2 Reading the measurement value of SMC

The registers defined here are used to read the measurementvalues of each SMC.

Start reg. Num-

ber of
reg.

Address 6 Physical unit Measurement

Figure 2.5.5.2.1: Definition of register at Address. Measurement value of each SMC.

Description Address Text Unit Min value Max value
SMC1 2472 R glass MOhm 30 600
SMC2 2504 R reference kOhm 0.25 100
SMC3 2536 R auxiliary kOhm 0.25 100
SMC4 2568 E pH vs. ref mV -900 900
SMC5 2600 E SG vs. ref mV -900 900
SMC6 2632 E aux vs. ref mV -50 50
SMC7 2664 E reference mV -900 900
SMC8 2696 pH act pH -0.5 14
SMC9 2728 T act K 253 403

Figure 2.5.5.2.2: Full list of register addresses for the measurement values of SMC1 to SMC9
Example:

Command: SMC1 read
Parameter: Unit Value Standard dev.
Format: Hex Float Float
Value:

Figure 2.5.5.2.3: Example to read register 2472. Physical unit is MOhm (0x8000), the measurement

value of SMC1 is 247.66 MOhm, standard deviation of SMC1 is 0.02 MOhm

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

value of SMC

Modbus address: 2472 Length: 6 Type: 3

0x8000 247.56 0.02

Standard
deviation

Read
function
code
3, 4 U/A/S none

access

Read

Write
access

624300/01 page 25 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.6 Configuration of the Measurement

This chapter describes the configuration of PMC1 and PMC6 by means of measurement parameters
(PA).

2.6.1 Available Parameters

In register 3072, all available parameters (PA) are given.

Start
register
3072 2 Available parameters (see figure 2.6.1.2) 3, 4 U/A/S none

Figure 2.6.1.1: Definition of register 3072.

Bit # Hex value Description Definition in pH ARC Sensors
0 (LSB) 0x0001 PA1 not available

7 0x0080 PA8 not available

8 0x0100 PA9 Moving average

9 0x0200 PA10 not available
10 0x0400 PA11 not available

11 0x0800 PA12 Moving average R

15 (MSB) 0x8000 PA16 not available

Figure 2.6.1.2: Bitwise definition of parameters PA1 to PA16, valid for pH ARC Sensors

Command: Available parameters
Parameter: Measurement

Format: Hex
Value:

Figure 2.6.1.3: Example to read the available parameters. The value 0x0900 corresponds to 0x0100

Number of
registers

parameters

0x0900

(PA9) + 0x0800 (PA12). Parameter 9 and 12 are available.

Reg1 / Reg2
(bitwise defined)

not available

not available

Modbus address: 3072 Length: 2 Type: 3

Modbus
function code

Read
access

Write
access

Read

Genereal note:

 PA1 to PA8 use FLOAT as data format for its values
 PA9 to PA16 use UNSIGNED INT as data format for its values.

624300/01 page 26 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.6.2 PA9: Moving Average

The pH ARC Sensor provides new pH readings every 3 seconds. One has the possibility to smoothen
the pH reading (PMC1) by means of a moving average applied to the 3-seconds-readings.

PA9 can be applied on 1 to 16 3-seconds-readings. The default value is 2.

Effect of Moving Average (n=1 vs n=16)

5.5

pH

pH

5.18

5.16

5.14

4.5

3.5

2.5

5.2

5

4

3

2

15:46

15:46

15:46

15:46

15:46

15:47

15:47

15:47

15:47

15:48

15:48

15:48

15:48

15:49

tim e

15:49

mov av = 1
mov av = 16

15:49

15:49

15:50

15:50

15:50

Effect of Moving Average (n=1 vs n=16)

mov av = 1
mov av = 16

5.12

5.1

15:46

15:46

15:46

15:46

15:46

15:47

15:47

15:47

15:47

15:48

15:48

15:48

15:48

15:49

15:49

15:49

15:49

15:50

15:50

15:50

tim e

Figure 2.6.2.1: Comparison of the response of a pH ARC Sensor to a change from pH 5.1 to pH 2.5,

using no moving average (n=1) or a moving average over 16 3-seconds-readings.

Using moving average, the short term signal stability can be improved; on the other hand, the response
time of the sensor increases with increasing moving average. A moving average over 16 samples
results in a response time of at least 48 s.

Note:

 PA9 is applied to both PMC1 and PMC6.

624300/01 page 27 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.6.2.1 Description of PA9 (Moving Average)

In register 3360, a plain text ASCII description of PA9 is given.

Start
register
3360 8 Description of PA9 3, 4 U/A/S none

Figure 2.6.2.1.1: Definition of register 3360.

Command: Moving average text
Parameter: Text
Format: Character
Value:

Figure 2.6.2.1.2: Example to read the description for “Moving average“.

2.6.2.2 Selecting the Physical Unit and Writing the Value for PA9

In register 3368, the available physical units for PA9 are defined.

Start
register
3368 2 Available physical units for PA9 3, 4 U/A/S none

Figure 2.6.2.2.1: Definition of register 3368.

Command: Moving average av. units
Parameter: Units
Format: Hex
Value:

Figure 2.6.2.2.2: Example to read the available physical units for PA9. The only one available here is

Number of
registers

Moving average

Number of
registers

0x01

“none”(0x01). For the definition of the physical units see chapter 2.5.1.

Reg1 … Reg8
16 ASCII characters

Modbus address: 3360 Length: 8 Type: 3

Reg1 / Reg2
(bitwise defined)

Modbus address: 3368 Length: 2 Type: 3

Modbus
function code

Modbus
function code

Read
access

Read
access

Write
access

Read

Write
access

Read

Start
register
3370 4 Select physical unit

Figure 2.6.2.2.3: Definition of register 3370. Only one bit for the physical unit can be set. PA9 can be

By writing to register 3370 the active physical unit for PA9 can be selected by choosing one of the
physical units that are defined in register 3368. The value of the parameter can be set as well.

Command: Moving average
Parameter: Unit Value
Format: Hex Decimal
Value:

Figure 2.6.2.2.4: Example to set the physical unit of PA9 to “none”(0x01) and the value of the moving

Number of
registers

set to the value 1-16. A value of 1 does not influence the response time of the sensor, a value of
16 increases the response time of the sensor to 48 s.

0x01 12

average to 12.

Reg1 / Reg2
(bitwise defined)

for PA9

Reg3 / Reg4 Modbus

function code
Value for PA9
(1-16, default: 2)

Modbus address: 3370 Length: 4 Type: 16

16 none S

Read
access

Write
access

Write

624300/01 page 28 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.6.2.3 Reading all Values for PA9

By reading register 3370, the active physical unit of measurement, the selected value, and the min and
max values can be read.

Start
register

3370 8 Physical

Figure 2.6.2.3.1: Definition of register 3370.

Command: Moving average
Parameter: Unit Value Min value Max value
Format: Hex Decimal Decimal Decimal
Value:

Figure 2.6.2.3.2: Example to read PA9. The physical unit is 0x01 (“none”), the value is 10 and the limit

Number of
registers

is 1 to 16.

Reg1 /
Reg2

unit

0x01 10 1 16

Reg3 /
Reg4

Current
value

Modbus address: 3370 Length: 8 Type: 3

Reg5 /
Reg6

Min
value

Reg7 /
Reg8

Max
value

Modbus
function
code
3, 4 U/A/S none

Read
access

Write
access

Read

624300/01 page 29 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.6.3 PA12: Moving Average R

pH ARC Sensors allow to have a separate moving average on secondary measurement values:

 Glass resistance
 Reference resistance

The moving average can be applied on 1 to 16 3-s measurement values. The default value is 4.
Especially if high resistancesare measured, it is recommended to choose a higher moving average.

2.6.3.1 Description of PA12 (Moving Average R)

In register 3456, a plain text ASCII description of PA12 is given.

Start
register
3456 8 Description of PA12 3, 4 U/A/S none

Figure 2.6.3.1.1: Definition of register 3456.

Command: Moving average text
Parameter: Text
Format: Character
Value:

Figure 2.6.3.1.2: Example to read the description for “Moving average R“.

2.6.3.2 Selecting the Physical Unit and Writing the Value for PA12

In register 3464, the available physical units for PA12 are defined.

Start
register
3464 2 Available physical units for PA12 3, 4 U/A/S none

Figure 2.6.3.2.1: Definition of register 3368.

Command: Moving average av. units
Parameter: Units
Format: Hex
Value:

Figure 2.6.3.2.2: Example to read the available physical units for PA12. The only one available here is

Number of
registers

Moving average R

Number of
registers

0x01

“none”(0x01). For the definition of the physical units see chapter 2.5.1.

Reg1 … Reg8
16 ASCII characters

Modbus address: 3456 Length: 8 Type: 3

Reg1 / Reg2
(bitwise defined)

Modbus address: 3464 Length: 2 Type: 3

Modbus
function code

Modbus
function code

Read
access

Read
access

Write
access

Read

Write
access

Read

Start
register
3466 4 Select physical unit

Figure 2.6.3.2.3: Definition of register 3466. Only one bit for the physical unit can be set. PA12 can be

624300/01 page 30 / 67

Number of
registers

set to the values 1-16.

Reg1 / Reg2
(bitwise defined)

for PA12

Reg3 / Reg4 Modbus

function code
Value for PA12
(1-16, default: 4)

16 none S

Read
access

Write
access

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

By writing to register 3466, the active physical unit for PA12 can be selected, by choosing one of the
physical units that are defined in register 3464. The value of the parameter can be set as well.

Command: Moving average
Parameter: Unit Value
Format: Hex Decimal
Value:

Figure 2.6.3.2.4: Example to set the physical unit of PA12 to “none”(0x01) and the value of the moving

average R to 7.

2.6.3.3 Reading all Values for PA12

By reading register 3466, the active physical unit of measurement, the selected value, and the min and
max values can be read.

Start
register

3466 8 Physical

Figure 2.6.3.3.1: Definition of register 3466.

Command: Moving average
Parameter: Unit Value Min value Max value
Format: Hex Decimal Decimal Decimal
Value:

Figure 2.6.3.3.2: Example to read PA12. The physical unit is 0x01 (“none”), the value is 7, and the

limits are 1 to 16.

0x01 7

Number of
registers

0x01 7 1 16

Reg1 /
Reg2

unit

Modbus address: 3466 Length: 4 Type: 16

Reg3 /
Reg4

Current
value

Modbus address: 3466 Length: 8 Type: 3

Reg5 /
Reg6

Min
value

Reg7 /
Reg8

Max
value

Modbus
function
code
3, 4 U/A/S none

Read
access

Write

Write
access

Read

624300/01 page 31 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7 Calibration

2.7.1 Available Calibration Points

In register 5120, the available number of Calibration Points (CP) for Primary Measurement Channel 1
(PMC1) is defined. 8 individual CP are theoretically possible.

Start
register
5120 2 Available number of CP for PMC1

Number of
registers

Reg1 / Reg2
(bitwise defined)

Modbus
function code

Read
access

Write
access

3, 4 U/A/S none

(see figure 2.7.1.2)

Figure 2.7.1.1: Definition of register 5120.

Bit # Hex value Description Definition in ARC Sensors

0 (LSB) 0x01 CP1 Calibration Point 1
1 0x02 CP2 Calibration Point 2

2 0x04 CP3 not available
… … … not available

5 0x20 CP6 Product Calibration

6 0x40 CP7 not available
7 (MSB) 0x80 CP8 not available

Figure 2.7.1.2: Bitwise definition of CP1 to CP8.

Command: Available cali points

Modbus address: 5120 Length: 2 Type: 3
Parameter: Points
Format: Hex
Value:

0x23

Figure 2.7.1.3: Example to read the available CPs. 0x23 = 0x01 (CP1) + 0x02 (CP2) + 0x20 (CP6).

Standard Calibration at 2 calibration points

Read

200

CP1

CP2

pH value

electrical potential glass vs. ref [mV]

150

100

50

0

-50

-100

-150

-200
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Figure 2.7.1.4: pH ARC Sensors allow 3 calibration points:

CP1 and CP2 are used for standard calibration (shown in this figure).
The product calibration CP6 is used to adjust the standard calibration function to specific process
conditions (the effect of CP6 is shown in Figure 2.7.3.2.1).

624300/01 page 32 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.2 Definitions of Calibration Points

2.7.2.1 Calibration Points 1 and 2 (Standard Calibration)

The limits for the calibration point 1 are defined in register 5152, for calibration point 2 in register 5184.

Start
register
5152 6 Physical unit

5184 6 Physical unit

Figure 2.7.2.1.1: Definition of register 5152 for CP1 and 5184 for CP2.

The only physical unit available for calibration is pH ! The physical unit defined in 5152, 5184 and 5312
for CP1, CP2 and CP6 is NOT linked to the physical unit defined for PMC1 in register 2090.
When performing a calibration while having the physical unit set to “mV”, the calibration status will
report “CP1: incorrect measurement unit”or “CP2: incorrect measurement unit”(see figure 2.7.4.1.1).

Command: Calibration limits CP1
Parameter: Unit Min value Max value
Format: Hex Float Float
Value:

Figure 2.7.2.1.2: Example to read the limits of CP1. Currently active physical unit is pH (0x01000). The

Number of
registers

Attention:

0x01000 0 0

min and max values are both 0, indicating, that calibration at CP1 can be performed only using
defined calibration standards having discrete pH values.

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

function code

currently
active for
CP1

currently
active for
CP2

Min value for
CP1 (in the
physical unit
as defined in
Reg1 and 2)
Min value for
CP2 (in the
physical unit
as defined in
Reg1 and 2)

Modbus address: 5152 Length: 6 Type: 3

Max value for
CP1 (in the
physical unit
as defined in
Reg1 and 2)
Max value for
CP2 (in the
physical unit
as defined in
Reg1 and 2)

3, 4 U/A/S none

3, 4 U/A/S none

Read
access

Read

Write
access

Command: Calibration limits CP2
Parameter: Unit Min value Max value
Format: Hex Float Float
Value:

Figure 2.7.2.1.3: Example to read the limits of CP2. The active physical unit is is pH (0x01000). The

min and max values are both 0, indicating, that calibration at CP2 can be performed only using
defined calibration standards having discrete pH values.

When initiating the calibration at CP1 and CP2, the measured pH and temperature have to be stable for
at least 3 minutes. The stability criteria are defined in register 5128:

Start
register
5128 4 Max. Drift PMC1

Figure 2.7.2.1.4: Definition of register 5128.

0x01000 0 0

Number of
registers

Reg1 / Reg2
(Float)

pH
[pH/min]

Modbus address: 5184 Length: 6 Type: 3

Reg3 / Reg4
(Float)
Max. Drift PMC6
Temperature
[K/min]

Modbus
function code
3, 4, 16 U/A/S S

Read
access

Read

Write
access

624300/01 page 33 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Command: Read calibration stability
Parameter: Max drift pH

[pH/min]
Format: Float Float
Value:

Figure 2.7.2.1.5: Example to read the calibration stability.

Command: Set calibration stability
Parameter: Max drift pH

Format: Float Float
Value:

Figure 2.7.2.1.6: Example to set the calibration stability.

Attention:

The stability criteria defined in register 5128 is valid for CP1 and CP2 only, but NOT for CP6.

2.7.2.2 Calibration Point 6 (Product Calibration)

The limits for calibration point 6 are given in register 5312.

0.1 0.5

[pH/min]

0.2 0.5

Modbus address: 5128 Length: 4 Type: 3
Max drift Temp
[K/min]

Modbus address: 5128 Length: 4 Type: 16
Max drift Temp
[K/min]

Read

Write

Start
register
5312 6 Physical unit

Figure 2.7.2.2.1: Definition of register 5312 for CP6.

Command: Calibration limits CP6
Parameter: Unit Min value Max value
Format: Hex Float Float
Value:

Figure 2.7.2.2.2: Example to read the limits of CP6. The active physical unit is pH, the min value is pH

Number of
registers

0x01000 0 14

0 and the max value is pH 14.

Note: the definition of min and max is different than the one for CP1 / CP2, because CP6 can be

set to any pH value.

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

function code

currently
active for
CP6

Min value for
CP6 (in the
physical unit
as defined in
Reg1 and 2)

Modbus address: 5312 Length: 6 Type: 3

Max value for
CP6 (in the
physical unit
as defined in
Reg1 and 2)

3, 4 U/A/S none

Read
access

Read

Write
access

624300/01 page 34 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.3 Calibration Procedure

2.7.3.1 Calibration at CP1 and CP2 (Standard Calibration)

The ARC Sensor family has a unique calibration routine. When initiating the calibration, the data set of
the sensor is automatically traced back within the last 3 minutes and a decision is made immediately if
the calibration is successful or not. The operator therefore gets an immediate result. The criteria for a
successful calibration are:

 the stability of pH value and temperature over the last 3 minutes (see register 5128)
 the currently measured pH value fits to one of the calibration standardsdefined in the selected

set of calibration standards

 the limits of slope and offset at pH 7 have to be met

Standard Calibration at 2 calibration points

200
150

100

CP1

electrical potential glass vs. ref [mV]

50

0

-50

-100

-150

-200
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

CP2

pH value

Figure 2.7.3.1.1: Standard Calibration using CP1 and CP2.

CP1 and CP2 define a linear relationship between the electrical potential and the pH value. This
linear calibration function is defined by an offset at pH 7 [mV] and a slope [mV/pH]. These two
values are stored in register 5448.
Note: the pH value of CP1 can be lower or higher than the pH value of CP2. However, the
difference in pH between CP1 and CP2 must always be greater than 1 pH unit.

Notes:

 In order to perform a standard calibration at CP1 and CP2, it is necessary to use commercially

available calibration standards. The operator is restricted to use those standards that are
defined in the six sets of calibration standards (see chapter 2.7.11).

 There are two ways of performing a standard calibration:

- standard calibration with automatic recognition of the calibration standard:
in this case, the sensor decides on itself in what calibration standard it is immersed.
The criteria to decide on is the electrical potential measured. The sensor checks the list
of calibration standardsthat are available for automatic recognition (see chapter

2.7.11)

- standard calibration with manual selection of the calibration standard:
the operator is selecting the calibration standard in which the sensor is immersed.

 Factory calibration is pH 4 at CP1 and pH 7 at CP 2.

624300/01 page 35 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Standard Calibration with Automatic Recognition of the Standard

Prior to calibration, the specialist selects - for each set of calibration standards - a list of calibration
standards allowed for automatic recognition (register 9530).
When the calibration is initiated, the sensor screens this list of allowed calibration standardsand
checks if the currently measured electrical potential is within the allowed range of electrical potentials,
defined for the individual calibration standards in this list.

If the sensor does find a corresponding calibration standard, the nominal pH value of the specific
calibration standard is assigned to the currently measured electrical potential. The temperature
dependency of the calibration standard is considered during the assignment.

Temperatue depend ency of Hamil ton pH buffer solutions

14

13

12

11

10

9

8

7

pH

6

5

4

3

2

1

0

0 10 20 30 40 50 60

Temper ature [°C]

Figure 2.7.3.1.2: Temperature dependency of the pH value of HAMILTON DURACAL calibration

standards.

If the sensor does not find any corresponding calibration standard, the bit representing the
corresponding status “no matching calibration standard”is set in the calibration status register.

Note that only the nominal value of the calibration standard is used for calibration. The actual value of
the calibration solution, which may deviate from the nominal value, is not taken into account and cannot
be set by the operator.

Standard Calibration with Manual Selection of the Calibration Standard

If the operator knows in what calibration standard the sensor is immersed, he can initiate the calibration
procedure by means of setting the pH value to the actual value of the calibration standard. The sensor
now screens the list of calibration standards that are allowed for manual selection (register 9530). If the
pH value entered by the operator fits in the allowed pH range of one of the allowed calibration
standards, the entered pH value is assigned to the currently measured electrical potential. The
temperature dependency of the calibration standard is considered during the assignment.

If the sensor does not find any corresponding calibration standard, the bit representing the
corresponding status “no matching calibration standard”is set in the calibration status register.

Note: using manual selection only, the actual pH value of the calibration standard can be set. However,
the actual value must be within the given tolerance of the standard in use.

624300/01 page 36 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Perform the following steps to do a standard calibration at CP1 and CP2:

Step1: Select the desired set of calibration standards (see chapter 2.7.11)

Step 2: Immerse the sensor into one of the calibration standards available in the selected set

Attention:

It is important that the pH ARC Sensor is immersed in a defined calibration standard at least 3
minutes BEFORE the calibration is started.

Step 3: Choose one of the calibration points CP1 or CP2.

Attention:

The assignment of both CP1 and CP2 to the same pH value is rejected.
Try to avoid the following situations:

For example, the sensor was calibrated earlier at pH 4 (CP1) and at pH 7 (CP2):

 You want to perform a new calibration at CP1: it is possible to assign CP1 to pH 4 or to

pH 10, but not to pH 7 (already used for CP2).

 You want to perform a new calibration at CP2: it is possible to assign CP2 to pH 7 or

pH 10, but not to pH 4 (already used for CP1).

 If you calibrate now CP1 at pH 10, pH 4 will later be free for selection at CP2. In this

case you can calibrate CP2 at pH 4 or pH 7, but not at pH 10 (CP1).

Step 4: Start the calibration (automatic recognition or manual selection)

The calibration is initiated at CP1 by writing to register 5162 or at CP2 by writing to register 5194.

Start
register
5162 2 pH value at CP1 (unit is always pH) 16 none A/S
5194 2 pH value at CP2 (unit is always pH) 16 none A/S

Figure 2.7.3.1.3: Definition of register 5162 and 5194. You have two options to enter the pH value:

Step 5: Read the calibration status (see chapter 2.7.4)

Step 6: Check the pH ARC Sensor’s quality indicator

Number of
registers

Automatic recognition: pH value=0: the sensor tries to assign the measured electrical potential to

one of the calibration standards available for automatic calibration.

Manual selection: enter the actual pH value at 25°C (the value must be within the tolerance

range of the nominal value of one of the calibration standardsavailable for manual selection)

Reg1 / Reg2 Modbus

function code

Read
access

Write
access

624300/01 page 37 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Examples: (Definitionsof register 5158 and 5190 used in these examples are given in chapter 2.7.4.1,
those for register 4872 in chapter 2.8.6)

Example to calibrate at CP1 with automatic recognition:

Command: Make calibration CP1
Parameter: pH value
Format: Float
Value:

Figure 2.7.3.1.4: Example to start the calibration at CP1, setting a value of 0 for automatic

recognition of the calibration standard.

Example to calibrate at CP2 with automatic recognition:

Command: Make calibration CP2
Parameter: pH value
Format: Float
Value:

Figure 2.7.3.1.5: Example to start the calibration at CP2, setting a value of 0 for automatic

recognition of the calibration standard.

Example to read the calibration status of CP1:

Command: Calibration status CP1
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.3.1.6: Example to read the calibration status of CP1 after calibration CP1 at 0 = auto.

All bits of CP1 are zero (0x00000000), indicating that the calibration was successful. The
physical unit of the last calibration is pH (0x00001000) and the assigned pH value is 4.01
at 25°C.

0

0

0x00000000 0x00001000 4.01

Modbus address: 5162 Length: 2 Type: 16

Modbus address: 5194 Length: 2 Type: 16

Modbus address: 5158 Length: 6 Type: 3

Write

Write

Read

Example to read the calibration status of CP2:

Command: Calibration status CP2
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.3.1.7: Example to read the calibration status of CP2 after calibrating CP2 at 0 = auto.

All bits of CP2 are zero (0x00000000), indicating that the calibration was successful. The
physical unit of the last calibration is pH (0x00001000) and the pH value is 7.

Example to calibrate at CP1 with manual selection of the calibration standard:

Command: Make calibration CP1
Parameter: pH value
Format: Float
Value:

Figure 2.7.3.1.8: Example to start the calibration at CP1, by means of manually selecting the

calibration standard HAMILTON DURACAL 4.01 (nominal value 4.01). The operator knows
from the certificate of the specific production lot that the actual pH value is 4.00.

0x00000000 0x00001000 7

4.00

Modbus address: 5190 Length: 6 Type: 3

Modbus address: 5162 Length: 2 Type: 16

Read

Write

624300/01 page 38 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Example to read the sensor’s quality indicator:

Command: Quality indicator
Parameter: Quality [%]
Format: Float
Value:

Figure 2.7.3.1.9: Example to read the sensor’s quality indicator

2.7.3.2 Calibration at CP6 (Product Calibration)

The product calibration is a process in order to adjust the measurement of a correctly calibrated pH
ARC Sensor to specific process conditions.
Product calibration is a two stage process:

1. An initial measurementis performed while the operator takes a sample of the process solution.
At that time point the pH ARC Sensor stores its raw measurement value, temperature and
operating hour in the memory.

While the operator takes the sample to the analytics lab for reference analysis the pH ARC
Sensor is still running on its prior standard calibration (CP1 and CP2) while the initial
measurement data for the ongoing product calibration is kept in the sensor’s memory.

2. When the result of the reference analysis is available this value is assigned, at a second time
point, to the former initial measurement data stored in the pH ARC Sensor.

100

Modbus address: 4872 Length: 2 Type: 3

Read

The sensor is now, after valid assignment, running on a calibration function which is
compensated for the correct process conditions. The product calibration (CP6) is now active.

Performing a Cancel command for the product calibration (CP6) brings the sensor back to its still stored
standard calibration (CP1 and CP2).

If a product calibration is still active and a standard calibration (CP1 or CP2) is performed the product
calibration (CP6) is cancelled.

If the operator needs to overrun an active product calibration (old CP6) by a new product calibration
(new CP6) the above process applies in the same way. After initial measurement the pH ARC Sensor
is still running on the first product calibration (old CP6) until a valid assignment has been done (new
CP6).

624300/01 page 39 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Product Calibration function

What happens to the pH ARC Sensor’s calibration function upon product calibration (CP6)?
A product calibration adds an offset to the linear calibration function defined by the standard calibration
at CP1 and CP2.

Product calibration of ARC pH sensors

200

150

100

Standard Calibration function

50

0

5 6 7 8 9 10

-50

Electrical potential [mV]

-100

-150

-200

CP1

CP6

CP2

pH

Figure 2.7.3.2.1: Effect of the product calibration CP6 on an existing standard calibration function

defined by CP1 and CP2.

The operator starts with a Standard Calibration with calibration points CP1 and CP2:
CP1: pH value of calibration standard: 6 electrical potential: 64.2 mV

CP2: pH value of calibration standard: 9.21 electrical potential: -125.2 mV
The sensor internally calculates the calibration function, using the calibration points CP1 and
CP2. The resulting calibration function, compensated to the standard temperature 25°C, is
shown as a straight line. The calibration function is described by two parameters: the offset at pH
7 and the slope.
Some weeks later, the operator believes that the Standard Calibration function is not correct
anymore. As the process is running and he is not able to perform a standard calibration under
defined conditions in the lab, he decides to perform a product calibration CP6, in other words
adjusting the standard calibration function to the process conditions:

CP6: pH value of product: 7.2 electrial potential: 5 mV
The sensor internally adds an offset to the calibration curve. The slope remains unchanged.

Another special feature of this calibration point is to switch off and back on again a product calibration.
These functions are called “restore standard calibration”and “restore product calibration”.

Note:
The sensor’s internal criteria for a successful product calibration are:

 the sensor is currently in an environment corresponding to the pH ARC Sensors measurement

range.

 the manually assigned pH value does not deviate more than 2 pH units from the value

measured prior the product calibration

624300/01 page 40 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

The different functionalities of product calibration (CP6) are accessible through the following sensor
commands:

 Initial measurement
 Assignment
 Cancel
 Restore standard calibration
 Restore product calibration

All commands are executed by writing a command value to the register 5340 except for assignment
where the calibration value is written to register 5322 (see below).

Definition of the commands for product calibration

The commands for register 5340 are defined as follows:

Code Hex Definition of commands
0x01 Perform initial measurement
0x02 Cancel an active product calibration
0x03 Restore a standard calibration from an active product calibration
0x04 Restore a product calibration from an active standard calibration

Figure 2.7.3.2.2: Definition of the commands related to the product calibration

Start
register
5340 2 Code as defined in Figure 2.7.3.2.2 3, 4, 16 A/S A/S

Figure 2.7.3.2.3: Definition of register 5340

2.7.3.2.1 Product calibration: Initial measurement

Upon process sample collection for laboratory analysis the command for initial measurement is sent to
the sensor.
This is achieved by writing the command 0x01 to register 5340 which performs the initial measurement
and stores the corresponding measurement values in the sensor.

Command: CP6: Initial measurement
Parameter: Command
Format: Hex
Value:

Figure 2.7.3.2.1.1: Example to start the product calibration procedure. Writing the command code 0x01

After successful initial measurement the corresponding calibration status (register 5318, figure

2.7.4.2.1) is “CP6 initial measurement”(0x08000000) (see figure 2.7.4.1.1).
The sensor continues measuring using the prior standard calibration.

Number of
registers

0x01

(initial measurement) to the CP6 command register 5340.

Reg1 / Reg2 Modbus

Modbus address: 5340 Length: 2 Type: 16

function code

Read
access

Write
access

Write

624300/01 page 41 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.3.2.2 Product calibration: Assignment

After successful initial measurement a correct value must be assigned to the initially stored
measurement data.
This is achieved by writing the correct calibration value to register 5322.

Start
register
5322 2 pH value [pH] 16 none A/S

Figure 2.7.3.2.2.1: Definition of register 5322

Command: CP6: Assignment
Parameter: Value
Format: Float
Value:

Figure 2.7.3.2.2.2: Example to assign a calibration value to the above performed initial measurement.

From now on the sensor is measuring using the here performed product calibration.
The calibration status (register 5318) is 0x14000000 meaning that a correct value has been assigned

and that the product calibration is active (see figure 2.7.4.1.1).

2.7.3.2.3 Product calibration: Cancel

To cancel an active product calibration or an active initial measurement the command 0x02 is written to
register 5340.

Number of
registers

7.2

This is achieved by writing the correct pH value.

Reg1 / Reg2 Modbus

Modbus address: 5322 Length: 2 Type: 16

function code

Read
access

Write
access

Write

Command: CP6: Cancel
Parameter: Command
Format: Hex
Value:

Figure 2.7.3.2.3.1: Example to cancel an active product calibration or an initial measurement.Writing

the command 0x02 (cancel) to register 5340.

Performing this action the product calibration or any initial measurements are canceled. The values of
the prior product calibration are removed from the sensor’s memory. From now on the sensor is
measuring using its prior CP1 / CP2 standard calibration.

The sensor’s calibration status (register 5318) will be reading 0x00 again (see figure 2.7.4.1.1).

0x02

Modbus address: 5340 Length: 2 Type: 16

Write

624300/01 page 42 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.3.2.4 Product calibration: Restore standard calibration

If a product calibration is active this product calibration can be temporarily switched off by writing the
command 0x03 to register 5340.
Performing this action the values of the product calibration remain stored in the sensor’s memory.

Command: CP6: Restore standard
Parameter: Command
Format: Hex
Value:

Figure 2.7.3.2.4.1: Example to restore a standard calibration from an active product calibration. Writing

command 0x03 (restore standard calibration) to register 5340.

From now on the sensor is measuring using its prior CP1 / CP2 standard calibration.
The sensor’s calibration status (register 5318) will be reading “CP6 assigned”(0x10000000) meaning
that a valid assignment for a product calibration is available in the sensor’s memory (see figure

2.7.4.1.1).

2.7.3.2.5 Product calibration: Restore product calibration

If a valid but inactivated product calibration is available in the sensors memory, the calibration status is
reading “CP6 assigned”(corresponding to 0x10000000, see figure 2.7.4.1.1), this stored product
calibration can be restored or reactivated by writing command 0x04 to register 5340.

Command: CP6: Restore product
Parameter: Command
Format: Hex
Value:

Figure 2.7.3.2.5.1: Example to restore an available product calibration from an active standard

calibration. Writing command 0x04 (restore product calibration) to register 5340.

0x03

0x04

Modbus address: 5340 Length: 2 Type: 16

Modbus address: 5340 Length: 2 Type: 16

Write

Write

From now on the sensor is measuring using its prior CP6 product calibration.
The sensors calibration status (register 5318) will be reading 0x14000000 (corresponding to “CP6
assigned”and “CP6 active”, see figure 2.7.4.1.1) again.

If this command is performed without available product calibration in the sensor’s memory the sensor
will respond with a Modbus exception since this command is not valid.

624300/01 page 43 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.4 Reading the Calibration Status

2.7.4.1 Reading the Calibration Status of CP1 and CP2

A standard calibration is not always successful. In order to analyze what has gone wrong, two different
calibration status registers can be read:

 Register 5158 for CP1
 Register 5190 for CP2

Note

Registers 5158 and 5190 contain the same information!

Bit # Hex value Definition
0 (LSB) 0x00000001 CP1: difference between CP1 and CP2 < pH 1.0
1 0x00000002 CP1: no matching calibration standard
2 0x00000004 CP1: actual temperature reading is too low
3 0x00000008 CP1: actual temperature reading is too high
4 0x00000010 CP1: temperature reading during calibration is not stable
5 0x00000020 CP1: offset a pH 7 is too low or slope is too low
6 0x00000040 CP1: offset a pH 7 is too high or slope is too high
7 0x00000080 CP1: pH reading during calibration is not stable
8 0x00000100 CP2: difference between CP2 and CP1 < pH 1.0
9 0x00000200 CP2: no matching calibration standard
10 0x00000400 CP2: actual temperature reading is too low
11 0x00000800 CP2: actual temperature reading is too high
12 0x00001000 CP2: temperature reading during calibration is not stable
13 0x00002000 CP2: offset a pH 7 is too low or slope is too low
14 0x00004000 CP2: offset a pH 7 is too high or slope is too high
15 0x00008000 CP2: pH reading during calibration is not stable
… not available
24 0x01000000 CP6: out of calibration range
25 0x02000000 CP6: out of range
26 0x04000000 CP6: active
27 0x08000000 CP6: initial measurement
28 0x10000000 CP6: assigned

not available
30 0x40000000 CP2: incorrect measurement unit
31 0x80000000 CP1: incorrect measurement unit

Figure 2.7.4.1.1: Definition of the status for register 5158, 5190 and 5318 (see Figure 2.7.4.1.2 and

2.7.4.2.1).

Start
register

5158 6 Status CP1

5190 6 Status CP2

Figure 2.7.4.1.2: Definition of register 5158 for CP1 and register 5190 for CP2.

624300/01 page 44 / 67

Number of
registers

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

(see figure

2.7.4.1.1)

(see figure

2.7.4.1.1)

Physical unit of
the last
successful
calibration CP1
(always pH)
Physical unit of
the last
successful
calibration CP2
(always pH)

pH value of the
last successful
calibration CP1

pH value of the
last successful
calibration CP2

Read
function
code
3, 4 U/A/S none

3, 4 U/A/S none

access

Write
access

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Command: Calibration status CP1
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.1.3: Example to read the calibration status of CP1 after calibration CP1 at 0 = auto. The

status message is: “CP1 pH reading during calibration is not stable”(0x00000080). The physical
unit of the last successful calibration is pH (0x00001000) and the last successful calibration has
been performed at pH 4.01.

Command: Calibration status CP2
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.1.4: Example to read the calibration status of CP2 after calibrating CP2 at 0 = auto. All bits

of CP2 are zero (0x00000080), indicating that the calibration was successful. The physical unit of
the last calibration is pH (0x00001000) and the last successful calibration has been performed at
pH 7.

Command: Calibration status CP2
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.1.5: Example to read the calibration status of CP2 after attempt to calibrate CP2 at pH

4.01, which is the same as CP1. The value is 0x00000180 = 0x00000080 + 0x00000100. Shown
is still 0x00000080 of CP1 and new 0x00000100 of CP2, which says: “CP2 space to CP1 < pH

1.0”.

0x00000080 0x00001000 4.01

0x00000080 0x00001000 7

0x00000180 0x00001000 7

Modbus address: 5158 Length: 6 Type: 3

Modbus address: 5190 Length: 6 Type: 3

Modbus address: 5190 Length: 6 Type: 3

Read

Read

Read

2.7.4.2 Reading the Calibration Status of CP6 (Product Calibration)

The calibration status and the current state of the product calibration process (CP6) is read in the
calibration status register for CP6 (register 5318).

Start
register

5318 6 Status CP6

Figure 2.7.4.2.1: Definition of register 5318 for CP6. For examples, see following chapters.

Number of
registers

Reg1 / Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus

function
code

(see figure

2.7.4.1.1)

Physical unit of
the last
successful
calibration CP6
(always pH)

pH value of the
last successful
calibration CP6

3, 4 U/A/S none

Read
access

Write
access

624300/01 page 45 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.4.2.1 Product calibration: Initial measurement

Calibration status after initial measurement command under conditions outside the valid calibration
range for CP6 (defined in register 5312):

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.1.1: Example to read the calibration status of CP6 after having performed an initial

measurement at CP6 under measurement conditions outside the calibration range for CP6.
The status says: “CP6: out of calibration range”(0x01000000). The last successful calibration
has been performed at pH 4.01.
The initial measurementin this case was not successful.
The sensor is still running on its prior standard calibration.

Calibration status after successful initial measurement:

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.1.2: Example to read the calibration status of CP6 after having performed an initial

measurement at CP6 under correct measurement conditions.
The status says: “CP6: initial measurement”(0x08000000). The last successful calibration has
been performed at pH 4.01.
The initial measurementin this case was successful.
The sensor is still running on its prior standard calibration until a valid calibration value has been
assigned to this initial measurement values.

0x01000000 0x00001000 4.01

0x08000000 0x00001000 4.01

Modbus address: 5318 Length: 6 Type: 3

Modbus address: 5318 Length: 6 Type: 3

Read

Read

2.7.4.2.2 Product calibration: Assignment

Calibration status after invalid assignment:

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.2.1: Example to read the calibration status of CP6 after having performed a valid initial

measurement at CP6 and an invalid assignment.
The status says: “CP6: out of range”(0x02000000) and “CP6: initial measurement”
(0x08000000). The last successful calibration has been performed at pH 4.01
The initial measurementin this case is still valid and available for further assignment of a product
calibration value. The here performed assignment was not successful. The sensor remains
running on its prior standard calibration.

Calibration status after valid assignment:

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.2.2: Example to read the calibration status of CP6 after having performed an initial

measurement at CP6 and a valid assignment to pH 4.5.
The status says: “CP6: active”(0x04000000) and “CP6: assigned”(0x10000000). The last
successful calibration corresponding to the here performed assignment has been performed at
pH 4.5.

0x0A000000 0x00001000 4.01

0x14000000 0x00001000 4.5

Modbus address: 5318 Length: 6 Type: 3

Modbus address: 5318 Length: 6 Type: 3

Read

Read

624300/01 page 46 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

The here performed assignment was successful. The sensor is running using a valid product
calibration.

2.7.4.2.3 Product calibration: Cancel

Calibration status after cancelling an active product calibration:

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.3.1: Example to read the calibration status of CP6 after having performed a cancel

command at CP6.
The status reports no messages. The last successful calibration at CP6 has been performed at
pH 4.5.
The sensor is running on a valid standard calibration and no product calibration is stored.

2.7.4.2.4 Product calibration: Restore standard calibration

Calibration status after restoring a standard calibration from an active product calibration:

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.4.1: Example to read the calibration status of CP6 after having restored the standard

calibration from an active product calibration (CP6).
The status says: “CP6 assigned”(0x10000000). The last successful calibration at CP6 has been
performed at pH 4.5.
The sensor is running on a valid standard calibration but a valid product calibration is still
available in the sensor.

0x00000000 0x00001000 4.5

0x10000000 0x00001000 4.5

Modbus address: 5318 Length: 6 Type: 3

Modbus address: 5318 Length: 6 Type: 3

Read

Read

2.7.4.2.5 Product calibration: Restore product calibration

Calibration status after restoring an available product calibration from an active standard calibration:

Command: Calibration status CP6
Parameter: Status Unit Value
Format: Hex Hex Float
Value:

Figure 2.7.4.2.5.1: Example to read the calibration status of CP6 after having restored an available

product calibration (CP6) from an active standard calibration (CP1 / CP2).
The status says: “CP6: active”(0x04000000) and “CP6: assigned”(0x10000000). The last
successful calibration corresponding to the here performed assignment has been performed at
pH 4.5.
The sensor is running on a valid product calibration again.

624300/01 page 47 / 67

0x14000000 0x00001000 4.5

Modbus address: 5318 Length: 6 Type: 3

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.5 Currently active Calibration Parameters part 1

In registers 5164 (CP1), 5196 (CP2) and 5324 (CP6) the currently active calibration parameters part 1
are stored. These registers contain the values for temperature, number of calibrations and operating
hour upon calibration.

Start
register

5164 8 Unit of

5196 8 Unit of

5324 8 Unit of

Figure 2.7.5.1: Definition of register 5164 for CP1, 5196 for CP2 and 5324 for CP6.

Command: Calibration CP1 values
Parameter: Unit of temperature Temperature Number of cali Operating hour
Format: Hex Float Decimal Float
Value:

Figure 2.7.5.2: Example to read the calibration values for CP1. The physical unit is °C (0x00000004),

Number
of
registers

0x00000004 24.35184 6 23.78

the temperature is 24.35184 °C, the number of calibrations at CP1 is 6 and the operating hour is

23.78 h.

Reg1 / Reg2 Reg3 /

Reg4

Value of
temperature for
CP1 (bitwise
defined)

temperature for
CP2 (bitwise
defined)

temperature for
CP6 (bitwise
defined)

temperature

of CP1

Value of

temperature

of CP2

Value of

temperature

of CP6

Modbus address: 5164 Length: 8 Type: 3

Reg5 /
Reg6

Number of
calibrations
at CP1

Number of
calibrations
at CP2

Number of
calibrations
at CP6

Reg7 /
Reg8

Operating
hour for
CP1

Operating
hour for
CP2

Operating
hour for
CP6

Modbus
function
code
3, 4 U/A/S none

3, 4 U/A/S none

3, 4 U/A/S none

Read
access

Read

Write
access

Command: Calibration CP2 values
Parameter: Unit of temperature Temperature Number of cali Operating hour
Format: Hex Float Decimal Float
Value:

Figure 2.7.5.3: Example to read the calibration values for CP2. The physical unit is °C (0x00000004),

the temperature is 24.37691 °C, the number of calibrations at CP1 is 5 and the operating hour is

16.45 h.

Command: Calibration CP6 values
Parameter: Unit of temperature Temperature Number of cali Operating hour
Format: Hex Float Decimal Float
Value:

Figure 2.7.5.4: Example to read the calibration values 1 for CP6. The physical unit is °C (4), the

temperature is 29.93 (°C), the number of calibrations at CP1 is 12 and the operating hour is

379.51 (h).

0x00000004 24.37691 5 16.45

0x00000004 29.93368 12 379.5167

Modbus address: 5196 Length: 8 Type: 3

Modbus address: 5324 Length: 8 Type: 3

Read

Read

2.7.6 Currently active Calibration Parameters part 2

Registers 5172 (CP1), 5204 (CP2) and 5332 (CP6) are not defined for pH ARC Sensors, as they
document atmospheric pressure and salinity used for VISIFERM DO / VISIFERM DO ARC Sensors
only.

624300/01 page 48 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.7 Currently active Calibration Parameters part 3

In register 5520, 5528 and 5560 the pH value of the used calibration standards, the electrical potential
of the pH sensor and the temperature upon calibration are stored.

Start
register

5520 8 pH value of

5528 8 pH value of

5560 8 pH value of

Figure 2.7.7.1: Definition of register 5520, 5528 and 5560.

Command: Act calibration CP1
Parameter: pH CP1 [pH] Voltage CP1 [mV] Temp CP1 [K] free
Format: Float Float Float Float
Value:

Figure 2.7.7.2: Example to read the actual calibration values of CP1.

Command: Act calibration CP2
Parameter: pH CP2 [pH] Voltage CP2 [mV] Temp CP2 [K] free
Format: Float Float Float Float
Value:

Figure 2.7.7.3: Example to read the actual calibration values of CP2.

Number
of
registers

4.003401 179.927 297.1378 0

7.006804 3.099747 296.6901 0

Reg1 /
Reg2

calibration
standard at
CP1 [pH]

calibration
standard at
CP2 [pH]

product at
CP6 [pH]

Reg3 /
Reg4

Electrical
potential at
CP1
[mV]
Electrical
potential at
CP2
[mV]
Electrical
potential at
CP6 [mV]

Modbus address: 5520 Length: 8 Type: 3

Modbus address: 5528 Length: 8 Type: 3

Reg5 /
Reg6

Electrical
potential at
CP1
[mV]
Electrical
potential at
CP2
[mV]
Electrical
potential at
CP6 [mV]

Reg7 /
Reg8

free 3, 4 A/S none

free 3, 4 A/S none

free 3, 4 A/S none

Modbus
function
code

Read
access

Write
access

Read

Read

Command: Act calibration CP6
Parameter: pH CP6 [pH] Voltage CP6 [mV] Temp CP6 [K] free
Format: Float Float Float Float
Value:

Figure 2.7.7.4: Example to read the actual calibration values of CP6.

7.1 5.10469 298.3302 0

Modbus address: 5560 Length: 8 Type: 3

Read

2.7.8 Currently active Calibration Parameters part 4

For standard calibration (CP1 / CP2) register 5448 documents offset at pH7 and slope:

Start
register

5448 6 Offset at

Figure 2.7.8.1: Definition of register 5448.

Command: Calculated cali values
Parameter: Offset at pH 7

Format: Float Float Float
Value:

Figure 2.7.8.2: Example to read register 5448: offset at pH 7 is 3.6 mV; slope is -59.5 mV/pH; reference

Number
of
registers

[mV]

3.607782 -59.47631 298.15

temperature is 298.15 K (=25°C)

Reg1 / Reg2
(Float)

pH 7 [mV]

Reg3 / Reg4
(Float)

Slope (25 °C)
[mV/pH]

Modbus address: 5448 Length: 6 Type: 3

Slope
[mV/pH]

Reg5 / Reg6
(Float)

Reference
temperature [K]

Ref temp
[K]

Modbus
function
code
3, 4 U/A/S none

Read
access

Write
access

Read

624300/01 page 49 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.9 Special Commands for Calibration with VISICAL

The VISICAL calibration device allows calibration of pH ARC Sensors at CP1 or CP2. The pH ARC
Sensor’s associated calibration parameters for CP1 and CP2 are those predefined and stored in
corresponding registers of the sensor.
Register 5164 defines the pH value for CP1 and register 5196 defines the pH value for CP2, which are
only valid for use with VISICAL. The same calibration limits for the pH value are used as for standard
calibration at CP1 and CP2 (register 5152 and 5184 respectively).

Attention:

 It is not possible to perform a product calibration using VISICAL.
 Physical unit is fixed to pH by definition.

Start
register
5180 2 pH value at CP1 (default: pH 4.00) 3, 4, 16 U/A/S S
5212 2 pH value at CP2 (default: pH 7.00) 3, 4, 16 U/A/S S

Figure 2.7.9.1: Definition of register 5180 for CP1 and 5212 for CP2.

Command: VISICAL CP1
Parameter: Value [pH]
Format: Float
Value:

Figure 2.7.9.2: Example to read the pH value valid for CP1. It is 4.00. Accordingly, the next time when a

Command: VISICAL CP2
Parameter: Value [pH]
Format: Float
Value:

Figure 2.7.9.3: Example to set the pH value valid for CP2.

Command: VISICAL CP2
Parameter: Value [pH]
Format: Float
Value:

Figure 2.7.9.4: Example to read the pH value valid for CP2. It is 7.00. Accordingly, the next time when a

Number of
registers

4.00

calibration is started using VISICAL at LOW, a calibration with manual selection is performed,
using the calibration standard at pH 4. The operator has to make sure that - within the selected
set of calibration standards - a standard at pH 4 is selected for manual selection.

7.00

7.00

calibration is started using VISICAL at HIGH, a calibration with manual selection is performed,
using the calibration standard at pH 7. The operator has to make sure that - within the selected
set of calibration standards - a standard at pH 7 is selected for manual selection.

Reg1 / Reg2 Modbus

function code

Modbus address: 5180 Length: 2 Type: 3

Modbus address: 5212 Length: 2 Type: 16

Modbus address: 5212 Length: 2 Type: 3

Read
access

Write
access

Read

Write

Read

624300/01 page 50 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.10 Calibration Standards

2.7.10.1 Available Sets of Calibration Standards

pH ARC Sensors can store and operate six different sets of calibration standards each having max 12
calibration standards. Before calibration the operator has to select one defined set to operate with.
Default setting is the HAMILTON set of calibration standards.
The operator can change the selection of sets at any time, without compromising prior calibration data
at CP1 / CP2.

In register 9472 the available sets of calibration standards are defined.

Start
register
9472 2 Available calibration standard sets 3, 4 U/A/S none

Figure 2.7.10.1.1: Definition of register 9472.

Bit # Hex value Description Definition

0 (LSB) 0x00000001 Set 1 HAMILTON

1 0x00000002 Set 2 MERCK TITRISOL
2 0x00000004 Set 3 DIN 19267
3 0x00000008 Set 4 NIST Standard
4 0x00000010 Set 5 METTLER-TOLEDO
5 0x00000020 Set 6 RADIOMETER

Figure 2.7.10.1.2: Definition of available sets of calibration standards.

Command: Available cali sets
Parameter: Calibration sets
Format: Hex
Value:

Figure 2.7.10.1.3: Example to read the available calibration sets: Set 1 (0x00000001) + set 2

In register 9474 the selected set of calibration standardsis defined.

Start
register
9474 2 Selected set of calibration standard 3, 4 U/A/S S

Figure 2.7.10.1.4: Definition of register 9474. Only one bit can be set.

Number of
registers

0x0000003F

(0x00000002) + set 3 (0x00000004) + set 4 (0x00000008) + set 5 (0x00000010) + set 6
(0x00000020), in total 0x0000003F.

Number of
registers

Reg1 / Reg2
(Bit, see Figure 2.7.10.1.2)

Modbus address: 9472 Length: 2 Type: 3

Reg1 / Reg2
(Bit, see Figure 2.7.10.1.2)

Modbus
function code

Modbus
function code

Read
access

Read
access

Write
access

Read

Write
access

Command: Selected set of cal stand.
Parameter: Calibration set
Format: Hex
Value:

Figure 2.7.10.1.5: Example to read the selected set of calibration standards. Set 1 (HAMILTON)

(0x00000001) is active.

Command: Select set of cal stand.
Parameter: Calibration set
Format: Hex
Value:

Figure 2.7.10.1.6: Example to set the calibration standard set to DIN 19267 (0x04).

624300/01 page 51 / 67

0x00000001

0x04

Modbus address: 9474 Length: 2 Type: 3

Modbus address: 9474 Length: 2 Type: 16

Read

Write

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.7.10.2 Definitions for Individual Sets of Calibration Standards

Once the operator has selected a set of calibration standards(register 9474) the register 9504 and
following give all information on the selected set of calibration standards.

Start
register
9504 8 Manufacturer of the selected set 3, 4 U/A/S none
9512 8 Info 1 of the selected set 3, 4 U/A/S none
9520 8 Info 2 of the selected set 3, 4 U/A/S none

Figure 2.7.10.2.1: Definition of registers 9504 to 9520.

Command: manufacturer of set
Parameter: Text
Format: Character
Value:

Figure 2.7.10.2.2: Example to read the description (in this case, the set 0x01 is selected)
Within one set of calibration standards, a maximum of 12 calibration standards are available. In the

following registers, the details of each calibration standard is given:

Start register Description
9536 Nominal value and tolerance of calibration standard 1
9552 Nominal value and tolerance of calibration standard 2
9568 Nominal value and tolerance of calibration standard 3
9584 Nominal value and tolerance of calibration standard 4
9600 Nominal value and tolerance of calibration standard 5
9616 Nominal value and tolerance of calibration standard 6
9632 Nominal value and tolerance of calibration standard 7
9648 Nominal value and tolerance of calibration standard 8
9664 Nominal value and tolerance of calibration standard 9
9680 Nominal value and tolerance of calibration standard 10
9696 Nominal value and tolerance of calibration standard 11
9712 Nominal value and tolerance of calibration standard 12

Figure 2.7.10.2.3: Definition for the register range from 9536 until 9720.

Number of
registers

HAMILTON

Reg1 … Reg8
(16 ASCII characters)

Modbus address: 9504 Length: 8 Type: 3

Modbus
function code

Read
access

Write
access

Read

Start
register

9536,
9552,

…

Figure 2.7.10.2.4: Definition for registers 9536 until 9720.

Command: Read standard 4
Parameter: Nominal value

Format: Float Float Float Float
Value:

Figure 2.7.10.2.5: Example to read the values for the calibration standard 4.

Number
of
registers
8 Calibr.

[pH]

4.01 0.02 180 80

Reg1 /
Reg2
(Float)

standard
nominal
value
[pH]

Reg3 /
Reg4
(Float)
Tolerance
of nominal
value (±)
[pH]

Modbus address: 9584 Length: 8 Type: 3
Tolerance
(±) [pH]

Reg5 /
Reg6
(Float)
Nominal
electrical
potential
[mV]

Reg7 /
Reg8
(Float)
Tolerance
of electrical
potential
(±) [mV]

Nominal electrical
potential
[mV]

Modbus
function
code
3, 4 U/A/S none

Tolerance of
electrical potential
(±) [mV]

Read
access

Write
access

Read

624300/01 page 52 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Register 9528 defines for the selected set of calibration standards:

 the available calibration standards for manual selection of the pH value
 the available calibration standards for automatic recognition of the pH value

Start
register
9528 2 Availability of the 12 cal. standards 3, 4 U/A/S none

Figure 2.7.10.2.6: Definition of register 9528

Command: Available standards
Parameter: Standard fields
Format: Hex
Value:

Figure 2.7.10.2.7: Example to read the information of register 9528. For the definition of the bits, see

Bit Hex code Index of Calibration

0 (LSB) 0x00000001 1 manual selection
1 0x00000002 2 manual selection
2 0x00000004 3 manual selection
3 0x00000008 4 manual selection
4 0x00000010 5 manual selection
5 0x00000020 6 manual selection
6 0x00000040 7 manual selection
7 0x00000080 8 manual selection
8 0x00000100 9 manual selection
9 0x00000200 10 manual selection
10 0x00000400 11 manual selection
11 0x00000800 12 manual selection
12-15 not available
16 0x00010000 1 automatic recognition
17 0x00020000 2 automatic recognition
18 0x00040000 3 automatic recognition
19 0x00080000 4 automatic recognition
20 0x00100000 5 automatic recognition
21 0x00200000 6 automatic recognition
22 0x00400000 7 automatic recognition
23 0x00800000 8 automatic recognition
24 0x01000000 9 automatic recognition
25 0x02000000 10 automatic recognition
26 0x04000000 11 automatic recognition
27 0x08000000 12 automatic recognition
28-31 not available

Figure 2.7.10.2.8: Availability / Selection for the 12 calibration standards within one given set.

Number of
registers

0x0FFF0FFF

Figure 2.7.10.2.8. The value 0x0FFF0FFF says that (for the selected set of calibration
standards):

 all 12 calibration standards are available for manual calibration
 all 12 calibration standardsare available for automatic recognition.

Bit 0-11 define availability of standards 1-12 for manual calibration.
Bit 16-27 define availability of standards 1-12 for automatic recognition
Register 9528: the corresponding calibration standard is available if bit is set
Register 9530: the corresponding calibration standard is selected if bit is set

Reg1 / Reg2
(Bit, see figure 2.7.10.2.8)

Modbus address: 9528 Length: 2 Type: 3

Standard within the
selected set

Modbus
function code

Calibration type

Read
access

Write
access

Read

624300/01 page 53 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

By means of register 9530, the specialist can define for each available calibration standard if the
specific standard is available.

Start
register
9530 2 Selected standard fields 3, 4 U/A/S S

Figure 2.7.10.2.9: Selected calibration standards within one given set.

Command: Selected standard fields
Parameter: Standard fields
Format: Hex
Value:

Figure 2.7.10.2.10: Example to read the selected calibration standards. The value 0x02480FFF says

Command: Selected standard fields
Parameter: Standard fields
Format: Hex
Value:

Figure 2.7.10.2.11: Example to set the standard fields to 12 calibration standards for manual calibration

The standards selected for automatic recognition must exhibit a difference in pH of at least 2 pH units.

Number of
registers

0x02480FFF

that:

 all 12 calibration standards are selected for manual selection
 only calibration standards 3, 7 and 10 are selected for automatic recognition

0x05540FFF

and calibration standard 3 (0x00040000), 5 (0x00100000), 7 (0x00400000), 9 (0x01000000) and
11 (0x04000000) for automatic recognition.

Attention:

Reg1 / Reg2
(Bit, see figure 2.7.10.2.8)

Modbus address: 9530 Length: 2 Type: 3

Modbus address: 9530 Length: 2 Type: 16

Modbus
function code

Read
access

Write
access

Read

Write

Figure 2.7.10.2.12: Illustration from the ARC Sensor Configurator software tool for registers 9528 and

9530. For this example, the HAMILTON set of calibration standard is selected.
On the left half of the figure, the availability of the calibration standards 1-12 is shown, as defined

in register 9528. In the left column, the availiability for manual calibration is shown (all
standards). In the right column, the availability for automatic recognition is given (all
standards as well).

On the right half of the figure, the individual selection defined by the specialist is shown as read

from register 9530. In the left column, the selection for manual selection is shown (all
standards). In the right column the selection for automatic recognition is given (calibration
standards 4, 7 and 10).

624300/01 page 54 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Manufacturer Availability for manual selection (left) and

automatic recognition (right)

HAMILTON

MERCK TITRISOL

DIN 19267

NIST STANDARD

624300/01 page 55 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Manufacturer Availability for manual selection (left) and

automatic recognition (right)

METTLER TOLEDO

RADIOMETER

Figure 2.7.10.2.13: Default definitions in register 9528 for all 6 sets of calibration standards available in

pH ARC Sensors.

624300/01 page 56 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.8 Sensor Status

2.8.1 Temperature Ranges

In registers 4608, 4612 and 4616 three different temperature ranges are defined:

 Operation –in this range the sensor will work properly (current output, Modbus

communication), except the measurement, which is stopped until the temperature is back in
the measurement range. In this case the last value of measurement will be frozen and sent to
analog interfaces.

 Measurement –in this range the sensor is able to measure.
 Calibration –in this range the sensor can be calibrated.

Start
register

4608 4 Operating
4612 4 Measurement
4616 4 Calibration

Figure 2.8.1.1: Definition of register 4608, 4612 and 4616.

Command: Operating T range
Parameter: Operating T min

Format: Float Float
Value:

Figure 2.8.1.2: Example to read the operating temperature values min and max.

Command: Measurement T range
Parameter: Measurement T

Format: Float Float
Value:

Figure 2.8.1.3: Example to read the measurement temperature values min and max.

Number of
registers

[°C]

-20 130

min [°C]

-20 130

Reg1 / Reg2 Reg3 / Reg4 Modbus

temperature min [°C]
temperature min [°C]
temperature min [°C]

function

code
Operating
temperature max [°C]
Measurement
temperature max [°C]
Calibration
temperature max [°C]

Modbus address: 4608 Length: 4 Type: 3
Operating T max
[°C]

Modbus address: 4612 Length: 4 Type: 3
Measurement T
max [°C]

3, 4 U/A/S none
3, 4 U/A/S none
3, 4 U/A/S none

Read
access

Write
access

Read

Read

Command: Calibration T range
Parameter: Calibration T min

[°C]
Format: Float Float
Value:

Figure 2.8.1.4: Example to read the calibration temperaturevalues min and max.

624300/01 page 57 / 67

5 50

Modbus address: 4616 Length: 4 Type: 3
Calibration T max
[°C]

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.8.2 Operating Hours and Counters

In register 4676 are given:

 total operating hours
 operating hours above max measurement temperature (see chapter 2.8.1)
 the operating hours above max operating temperature (see chapter 2.8.1)

In register 4682 are stored:

 number of power ups
 number of watchdog resets
 number of writing cycles to the sensor’s flash memory

In register 4688 are given:

 number of sterilizations in place (SIP) (see chapter 2.8.5)
 number of cleanings in place (CIP) (see chapter 2.8.5)

Start
register
4676 6 Operating

4682 6 Number of

4688 4 Number of

Figure 2.8.2.1: Definition of register 4676, 4682 and 4688.

Command: Operating hours
Parameter: Operating hours [h] Operating hours

Format: Float Float Float
Value:

Figure 2.8.2.2: Example to read the total operating hours, the operating hours above the max

Number of
registers

168.3667 0 0

measurement temperature and the operating hours above the max operating temperature.

Reg1 / Reg2 Reg3 / Reg4 Reg3 / Reg4 Modbus

function code

hours
[h]

Power ups

SIP cycles

Operating
hours above
max
measurement
temperature
[h]
Number of
Watchdog
resets

Number of
CIP cycles

Modbus address: 4676 Length: 6 Type: 3

above max
measurement
temperature
[h]

Operating
hours above
max
operating
temperature
[h]
Number of
Writing
cycles to
flash memory

- 3, 4 U/A/S none

Operating hours
above max
operating
temperature
[h]

3, 4 U/A/S none

3, 4 U/A/S none

Read
access

Read

Write
access

Command: Power & watchdog
Parameter: Number of Power

ups

Format: Decimal Decimal Decimal
Value:

Figure 2.8.2.3: Example to read the number of power ups, the number of watchdog resets and the

number of writing cycles to flash memory.

Command: SIP & CIP
Parameter: SIP cycles CIP cycles
Format: Decimal Decimal
Value:

Figure 2.8.2.4: Example to read the number of SIP cycles and the number of CIP cycles. For the

definition of SIP and CIP cycles see chapter 2.8.5.

624300/01 page 58 / 67

34 1 16

0 0

Modbus address: 4682 Length: 6 Type: 3
Number of
Watchdog resets

Modbus address: 4688 Length: 4 Type: 3

Number of Writing
cycles to flash
memory

Read

Read

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.8.3 Warnings

A “Warning”is a notification message which still allows further functioning of the system. This message
alerts the operator of a possible problem that could lead to uncertain results.

2.8.3.1 Currently Active Warnings

The currently active warnings are stored in register 4736.

Start
register

4736 8 Active

Figure 2.8.3.1.1: Definition of register 4736 (see chapter 2.8.3.3)

Command: Active warning
Parameter: W Measurement W Calibration W Interface W Hardware
Format: Hex Hex Hex Hex
Value:

Figure 2.8.3.1.2: Example to read the currently active warnings.

2.8.3.2 History of Warnings

The history of warnings is not implemented in pH ARC Sensors.

Number of
registers

0x00 0x00 0x00 0x00

Reg1 /
Reg2

warning
measure­ment
(bitwise
defined)

Reg3 /
Reg4

Active
warning
calibration
(bitwise
defined)

Modbus address: 4736 Length: 8 Type: 3

Reg5 /
Reg6

Active
warning
interface
(bitwise
defined)

Reg7 /
Reg8

Active
warning
hardware
(bitwise
defined)

Modbus
function
code
3, 4 U/A/S none

Read
access

Read

Write
access

2.8.3.3 Definition of Warnings

Bit # Hex Description

not available

Figure 2.8.3.3.1: Definition of warnings “measurement”. None is defined.

Bit # Hex Description
0 (LSB) 0x0001 PMC1 (pH) calibration recommended
1 0x0002 PMC1 (pH) last calibration not successful

Figure 2.8.3.3.2: Definition of warnings “calibration”.

Bit # Hex Description

not available

Figure 2.8.3.3.3: Definition of warnings “interface”. None is defined.

Bit # Hex Description

not available

Figure 2.8.3.3.4: Definition of warnings “hardware”. None is defined.

624300/01 page 59 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.8.4 Errors

An “Error”message indicates a serious problem of the sensor which does not allow further proper
functioning of the sensor. This problem must be solved.

2.8.4.1 Currently Active Errors

The currently active errors are stored in register 4800.

Start
register

4800 8 Active error

Figure 2.8.4.1.1: Definition of register 4800 (see chapter 2.8.4.3)

Command: Active errors
Parameter: E Measurement E Calibration E Interface E Hardware
Format: Hex Hex Hex Hex
Value:

Figure 2.8.4.1.2: Example to read the currently active errors.

2.8.4.2 History of Errors

The history of errors is not implemented in pH ARC Sensors.

Number
of
registers

0x00 0x00 0x00 0x00

Reg1 /
Reg2

measure­ment
(bitwise
defined)

Reg3 /
Reg4

Active error
calibration
(bitwise
defined)

Modbus address: 4800 Length: 8 Type: 3

Reg5 /
Reg6

Active error
interface
(bitwise
defined)

Reg7 /
Reg8

Active error
hardware
(bitwise
defined)

Modbus
function
code
3, 4 U/A/S none

Read
access

Read

Write
access

624300/01 page 60 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.8.4.3 Definition of Errors

Bit # Hex Description

not available
5 0x0000020 Glass resistance too high
6 0x0000040 Glass resistance too low
7 0x0000080 Reference electrode resistance too high
8 0x0000100 Reference electrode resistance too low

not available
15 0x0008000 Auxiliary electrode electrical potential too high
16 0x0010000 Auxiliary electrode electrical potential too low
17 0x0020000 Auxiliary electrode resistance too high
18 0x0040000 Auxiliary electrode resistance too low

not available
25 0x2000000 Temperature sensor defective

Figure 2.8.4.3.1: Definition of errors “measurement”.

Bit # Hex Description
1 0x0000002 Sensor failure (Quality value < 15%)

Figure 2.8.4.3.2: Definition of errors “calibration”.

Bit # Hex Description

not available

Figure 2.8.4.3.3: Definition of errors “interface”. None is defined.

Bit # Hex Description

not available
24 0x1000000 Internal communication error (betweenfront-end and user-end)

Figure 2.8.4.3.4: Definition of errors “hardware”.

624300/01 page 61 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.8.5 Reading Definition of SIP and CIP

pH ARC Sensor are counting special cleaning events such as sterilizations or cleaning cycles by
means of tracking typical temperature profiles (see chapter 2.8.2).

Register 4988 defines a typical temperature profile for SIP (sterilizationin place) and register 4996 for
CIP (cleaning in place). For the explanation the followingvalues are given:

CIP temperature min: 80 °C CIP temperature max: 100 °C CIP time min: 30 minutes
SIP temperature min: 120 °C SIP temperature max: 130 °C SIP time min: 30 minutes

CIP and SIP

140

120

100

80

60

Temperature [°C]

40

20

0

08:00

08:15

08:30

no SIP 1) SIP ok 3)

CIP ok 2)

08:45

09:00

09:15

09:30

09:45

10:00

10:15

10:30

10:45

11:00

11:15

11:30

11:45

12:00

Time

Figure 2.8.5.1: Definition of CIP and SIP cycles.

1) no SIP-cycle counted, because time too short <30 minutes.

2) CIP-cycle counted, because time >30 minutes and in CIP temperature range.

3) SIP-cycle counted, because time >30 minutes and in SIP temperature range.

4) no CIP-cycle counted, because of reaching the SIP-min limit.

no CIP 4) no CIP 4)

12:15

12:30

12:45

13:00

13:15

13:30

13:45

14:00

14:15

14:30

14:45

15:00

15:15

15:30

15:45

16:00

16:15

16:30

16:45

17:00

T CIP
T SIP
CIP min
CIP max
SIP min
SIP max

Start
register

Number
of

Reg1 /
Reg2

Reg3 /
Reg4

Reg5 /
Reg6

registers

4988 8 SIP

Tempera­ture min
[°C]

4996 8 CIP

Tempera­ture min
[°C]

SIP
Tempera­ture max
[°C]
CIP
Tempera-

-ture max
[°C]

SIP
Process
time min
[min]
CIP
Process
time min
[min]

Figure 2.8.5.2: Definition of register 4988 and 4996.

624300/01 page 62 / 67

Reg7 /
Reg8

Modbus
function

Read
access

code

Empty 3, 4 U/A/S S

Empty 3, 4 U/A/S S

Write
access

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Command: SIP definition
Parameter: T min [°C] T max [°C] Timemin [min] Empty
Format: Float Float Float Float
Value:

Figure 2.8.5.3: Example to write the SIP definitions.

Command: SIP definition
Parameter: T min [°C] T max [°C] Timemin [min] Empty
Format: Float Float Float Float
Value:

Figure 2.8.5.4: Example to read the SIP definitions.

Command: CIP definition
Parameter: T min [°C] T max [°C] Timemin [min] Empty
Format: Float Float Float Float
Value:

Figure 2.8.5.5: Example to write the CIP definitions.

Command: CIP definition
Parameter: T min [°C] T max [°C] Timemin [min] Empty
Format: Float Float Float Float
Value:

Figure 2.8.5.6: Example to read the CIP definitions.

120 130 30 0

120 130 30 0

80 100 30 0

80 100 30 0

Modbus address: 4988 Length: 8 Type: 16

Modbus address: 4988 Length: 8 Type: 3

Modbus address: 4996 Length: 8 Type: 16

Modbus address: 4996 Length: 8 Type: 3

Write

Read

Write

Read

2.8.6 Reading the Sensor’s Quality Indicator

In register 4872 the sensor’s quality indicator (0-100%) is given.

Start
register

4872 2 Quality [%] 3, 4 U/A/S none

Figure 2.8.6.1: Definition of register 4872.

Command: Quality indicator
Parameter: Quality [%]
Format: Float
Value:

Figure 2.8.6.2: Example to read the sensor’s quality indicator.
The sensor’s quality indicator is influenced by:

 Offset a pH 7
 Slope
 Errors

Number of
registers

100

Reg1 / Reg2
(Float)

Modbus
function
code

Modbus address: 4872 Length: 2 Type: 3

Read
access

Write
access

Read

624300/01 page 63 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

2.9 Sensor Identification and Information

2.9.1 General Information

General information about the sensor is available as shown in the figure below.

Start
register

1024 8 Userend FW Date 2010-04-28 3, 4 U/A/S none
1032 8 Userend FW EPHUM011 3, 4 U/A/S none
1040 8 Userend BL Date 2009-09-18 3, 4 U/A/S none
1048 8 Userend BL BL0UX012 3, 4 U/A/S none
1056 8 Userend P/N 242822/01 3, 4 U/A/S none
1064 8 Userend S/N not available 3, 4 U/A/S none
1072 8 Userend (space holder) not available 3, 4 U/A/S none
1080 8 Userend (space holder) not available 3, 4 U/A/S none
1088 8 Frontend FW Date 2009-09-16 3, 4 U/A/S none
1096 8 Frontend FW EPHFI010 3, 4 U/A/S none
1104 8 Frontend BL Date not available 3, 4 U/A/S none
1112 8 Frontend BL not available 3, 4 U/A/S none
1120 8 Frontend P/N 242828/00 3, 4 U/A/S none
1128 8 Frontend S/N not available 3, 4 U/A/S none
1136 8 Frontend (space holder) not available 3, 4 U/A/S none
1144 8 Frontend (space holder) not available 3, 4 U/A/S none

Figure 2.9.1.1: Definition of registers containing read-only sensor information.

Command: Userend Firmware
Parameter: Text
Format: Character
Value:

Figure 2.9.1.2: Example to read register 1032.

Number of
registers

EPHUM011

Reg1 … Reg8
(16 ASCII characters)

Modbus address: 1032 Length: 8 Type: 3

Example of content Modbus

function
code

Read
access

Write
access

Read

2.9.2 Sensor Identification

Start
register

1280 8 Part number 242111/01 3, 4 U/A/S none
1288 8 Sensor name Polilyte Plus 3, 4 U/A/S none
1296 8 Work order number 3214567 3, 4 U/A/S none
1304 8 Work order date 2010-04-30 3, 4 U/A/S none
1312 8 Serial number 0001001 3, 4 U/A/S none
1320 8 Manufacturer part 1 HAMILTON Bonaduz 3, 4 U/A/S none
1328 8 Manufacturer part 2 AG Switzerland 3, 4 U/A/S none
1336 8 Sensor type ARC e. pH Sensor 3, 4 U/A/S none
1344 8 Power supply 007..030V 0150mW 3, 4 U/A/S none
1352 8 Pressure range 0 ... 6 bar 3, 4 U/A/S none
1360 8 Sensor ID 242111-0001001 3, 4 U/A/S none
1368 8 a-length 120 3, 4 U/A/S none
1376 8 (space holder) not available 3, 4 U/A/S none
1384 8 Electrical connection VP 8.0 3, 4 U/A/S none
1392 8 Process connection PG 13.5 3, 4 U/A/S none
1400 8 Sensing material H-Glass 3, 4 U/A/S none

Figure 2.9.2.1: Definition of registers containing sensor identification.

Number of
registers

Reg1 … Reg8
(16 ASCII characters)

Example of content Modbus

function
code

Read
access

Write
access

624300/01 page 64 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Command: Serial number
Parameter: Text
Format: Character
Value:

Figure 2.9.2.2: Example to read register 1312.

0001001

Modbus address: 1312 Length: 8 Type: 3

Read

2.9.3 Free User Memory Space

These registers can be used to store any customer specific information in the sensor. There are
different registers which can be read by everybody, but only specific operators can write them.

Start
register

1536 8 Free user space U/A/S *FREE_USERSPACE* 3, 4, 16 U/A/S U/A/S
1544 8 Free user space U/A/S *FREE_USERSPACE* 3, 4, 16 U/A/S U/A/S
1552 8 Free user space U/A/S *FREE_USERSPACE* 3, 4, 16 U/A/S U/A/S
1560 8 Free user space U/A/S *FREE_USERSPACE* 3, 4, 16 U/A/S U/A/S
1568 8 Free user space A/S *FREE_USERSPACE* 3, 4, 16 U/A/S A/S
1576 8 Free user space A/S *FREE_USERSPACE* 3, 4, 16 U/A/S A/S
1584 8 Free user space A/S *FREE_USERSPACE* 3, 4, 16 U/A/S A/S
1592 8 Free user space A/S *FREE_USERSPACE* 3, 4, 16 U/A/S A/S
1600 8 Measuring point 242111-0001001 3, 4, 16 U/A/S S
1608 8 Free user space S *FREE_USERSPACE* 3, 4, 16 U/A/S S
1616 8 Free user space S *FREE_USERSPACE* 3, 4, 16 U/A/S S
1624 8 Free user space S *FREE_USERSPACE* 3, 4, 16 U/A/S S
1632 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1640 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1648 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1656 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1664 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1672 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1680 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1688 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1696 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1704 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1712 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1720 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1728 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1736 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1744 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none
1752 8 Free user space others *FREE_USERSPACE* 3, 4 U/A/S none

Figure 2.9.3.1: Definition of registers containing user information.

Number
of
registers

An important register is 1600, as it is the description of the measuring point. The information of
this register is displayed on the ARC View Handheld in order to identify individual sensors.

Reg1 … Reg8
(16 ASCII characters)

Example of content Modbus

function
code

Read
access

Write
access

Attention:
The Free User Memory Space is located in a memory which allows in total max 10’000 write
operations.

624300/01 page 65 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

Command: Info user
Parameter: Text
Format: Character
Value:

Figure 2.9.3.2: Example to write 16 ASCII characters to register 1568 with operator A or S.

Command: Info user
Parameter: Text
Format: Character
Value:

Figure 2.9.3.3: Example to read the register 1568 (written in figure 2.9.1.6).

Hello World

Hello World

Modbus address: 1568 Length: 8 Type: 16

Modbus address: 1568 Length: 8 Type: 3

2.10 System Commands

2.10.1 Recall Sensor’s Factory Settings

Using register 8192 you can recall the sensor manufacturer values (interfaces, calibration data and
passwords), except the SIP and CIP data which remain unchanged. By sending the recall value
“732255”, all configuration values will be set to default.

Write

Read

Start
register
8192 2 Recall by value 732255 16 none S

Figure 2.10.1.1: Definition of register 8192.

Command: Recall
Parameter: Recall
Format: Decimal
Value:

Figure 2.10.1.2: Example to write the restore command.

Number of
registers

732255

Reg1 / Reg2 Modbus

function code

Modbus address: 8192 Length: 2 Type: 16

Read
access

3 Abbreviations

AO Analog Output Interface
CP Calibration Point
ECS Electrochemical Sensor Interface
PMC Primary Measurement Channel
SMC Secondary Measurement Channel

Write
access

Write

624300/01 page 66 / 67

pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)

HAMILTON Bonaduz AG
Via Crusch 8
CH-7402 Bonaduz
Switzerland

Tel. [phone]
Fax [phone]

[e-mail] 05 May 2010
www.hamiltoncompany.com Manual P/N: 624300/01

624300/01 page 67 / 67