YOKOGAWA PH200 Instruction Manual

IM 12B6C2-E-H

6th edition

Instruction
Manual

Model PH200
2-wire pH transmitter

YOKOGAWA

FAIL

HOLD

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.

YES

NO

ENT

OUTPUT
SET HOLD
SERVICE

*

NO MODEYES

>

ENT>

MODE

TEMP.MAN

HOLD

pH
mV

OUTPUT HOLD

FLAG

MEASURED

VALUE DISPLAY

MESSAGE DISPLAY

KEY PROMPT FLAGS

SELECTION KEYS
YES : Accept setting
NO : Change to new setting

ADJUSTMENT KEYS
> : Choose digit for adjustment
^ : Adjust digit (to decrease pass

through zero)

ENT : Enter new value

NOTE: The first digit changes from 1, -1, - to blank

SELECT MODE
MEASURE/MAINTENANCE

Can be used to escape program at any
time

MANUAL TEMPERATURE

COMPENSATION FLAG

FAIL FLAG

MENU POINTER FLAGS

MENU FOR MAINTE­NANCE FUNCTIONS
(see chapter 5)

MENU FOR COMMIS­SIONING FUNCTIONS
(see chapter 4)

SELECT MODE
MEASURE/COMMISSIONING

IM 12B6C2-E-H

HOLD

pH
mV

TEMP.MAN

NO MODEYES

>

YES

FAIL

NO

ENT

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

ENT>

OUTPUT
SET HOLD
SERVICE

*

IM 12B6C2-H-H

CONTENTS

1. INTRODUCTION..................................................................1

1-1. Application......................................................................1

1-2. Required components for pH measurement...................1

1-3. Identification ...................................................................1

2. TECHNICAL SPECIFICATIONS...........................................2

2-1. General specifications .....................................................2

2-2. Functional description .....................................................3

3. INSTALLATION AND WIRING .............................................4

3-1. Installation and dimensions.............................................4

3-1-1. Installation site ...................................................4

3-1-2. Mounting methods.............................................4

3-2. Wiring of sensors............................................................6

3-2-1. General precautions...........................................6

3-2-2. Additional precautions for installations in

hazardous areas ................................................6

3-2-3. Liquid earth........................................................6

3-2-4. Access to terminal and cable entry....................6

3-2-5. Connection diagram for sensors........................7

3-3. Wiring of power supply...................................................8

3-3-1. General precautions...........................................8

3-3-2. Additional precautions for installations in

hazardous areas ................................................8

3-3-3. Connection of the power supply........................8

3-3-4. Switching the instrument on...............................8

4. COMMISSIONING..............................................................11

4-1. Operations overview .....................................................11

4-2. Output range adjustment.....................OUTPUT...........12

4-3. Set up the HOLD function ...................SET HOLD ........14

4-4. Sensor selection and diagnostics..................................16

4-4-1. Selection of measurement and reference

electrode..........................................................16

4-4-2. Selecting a temperature sensor .......................16

4-4-3. Off-line calibration checks................................16

4-4-4. On-line impedance chacks ..............................16

5. MAINTENANCE..................................................................17

5-1. Automatic calibration...........................AUT.CAL...........18

5-2. Manual calibration ...............................MAN.CAL .........20

5-3. Selecting a value to display .................DISPLAY ...........22

5-4. Temperature compensation.................TEMP ...............24

5-5. Hold output function.....................................................26

6. TROUBLE SHOOTING .......................................................28

6-1. Introduction ..................................................................28

6-2. Error messages and explanation...................................29

IM 12B6C2-E-H

7. SERVICE MODE.................................................................30

7-1. Introduction.................................................................30

7-2. Access to service settings...........................................31

7-3. Temperature function...................................................32

7-4. Temperature sensors...................................................32

7-5. Sensor checking..........................................................33

7-6. Display resolution ........................................................34

7-7. Signalling of fail condition ............................................34

7-8. Stabilization check .......................................................34

7-9. Auto return ..................................................................35

7-10.Buffer tables................................................................35

7-11.Temperature adjustment..............................................36

7-12. Manual adjustment of ITP, slope and

asymmetry potential....................................................36

7-13. Passwordprotection by three digit code......................37

7-14. Restore default settings ..............................................37

8. CLASSIFICATION...............................................................38

8-1. Cenelec........................................................................38

8-2. FM................................................................................39

9. CHANGE FROM PH TO ORP MEASUREMENT ..............40

9-1. How to change from pH measurement to

ORP measurement.......................................................40

9-2. Commissioning the transmitter .....................................40

9-3. Maintenance of the transmitter .....................................40

9-4. Special features............................................................40

9-5. Wiring diagram .............................................................41

9-6. Buffer values .................................................................41

APPENDIX A............................................................................42

IM 12B6C2-E-H

1-1. Application

The EXA PH200 transmitter is a 2-wire pH
instrument intended to be used in industrial
installations in the field. For easy maintenan­ce and operation it should be located close
to the sensors. It is powered from a remote
low voltage DC power supply through the 2­wire connection. The EXA PH200 is compa­tible with most commercial available pH sen­sors and fitting systems.
The instrument is available in two versions:

- A general purpose version for use in safe
areas.

- An intrinsically safe version for use in
hazardous areas. The instrument can then
be installed in Zone 1 with the sensors in
Zone 1 or Zone 0.

The micro-processor is used in this instru­ment for continuous sensor diagnostics,
flexible on site commissioning and fine tu­ning by advanced functions.

In general a pH loop can be set up for diffe­rent purposes:

- To be part of a total process control sys­tem

- To indicate dangerous limits of a process.

- To monitor product quality.

1-2. Required components for pH

measurement

1. A pH electrode and a reference electrode
or a combined pH-reference electrode.

2. A temperature sensor Pt100 (according
to IEC 751 or DIN) or Pt1000

3. A fitting for the above electrodes with
accessories

4. Signal cables with or without extension
boxes, etc.

5. The EXA PH200 2-wire transmitter with
mounting accessories for wall or pipe
mounting

6. A DC power supply (nominal 24 V DC)
with cabling and optional zener barriers
or an intrinsic safe power supply

7. Peripherals: e.g. strip-chart recorder,
panel indicator, PID-controller.

1-3. Identification

The instrument has an identification label,
which is fixed to the front plate.
This serves as a reference for the full model
code, power supply voltage and serial num­ber. This label also carries authorised marks
to certify compliance with the current regula­tory norms.

1

1. INTRODUCTION

MODEL
SERIAL NO.
SUPPLY

2-1. General specifications
A. Intrinsic safety

– BASEEFA : Certified by and meets the require-

ments of EEx [ia] ib IIC T4 of CENE­LEC
Certificate nr. : 89C2379)

– FM : For IS CL1, DIV1, GP ABCD

T3B for TA-30 to 70 °C
T4 for TA-30 to 40 °C
Approval report: J.I. 1Y1A7.AX

– CSA : For Ex[ia] Class 1, Div. 1, Groups C

and D, T4A
Approval file: LR 102851-1

B. Indicating range :-1 to +15 pH.
C. Transmission signal : 4 - 20 mA DC; max. load 550 Ω
D. Transmission range : 0 - 14 pH.

User programmable to any range
with a minimum span of 1 unit.

E. Power supply

– Model PH200G : 17 - 40 V DC,

dependent on load

– Model PH200S : 17 - 31,5 V DC,

dependent on load

F. Climatic conditions

– Ambient temperature : -10 to +55 °C
– Storage temperature : -30 to +70 °C
– Relative humidity : 10 to 90%
– Weather protection : Rain and dust-tight IP65 (NEMA 4X)

G. Housing

– Material : Cast aluminium with chemical resi-

stant coating
– Window : Flexible poly-carbonate
– Colours : Moss green/off-white
– Cable glands : Polyamide
– Cable entries : Two

h

” glands

Hose connection optional
– Earth connection : For external ground

H. Mounting possibilities

– Surface mounting : Two M6 bolts, 9 mm length
– Wall/Pipe mounting : With optional mounting kit
– Sunlight protection : With optional hood
– Panel mounting : 154 x 172 octagonal with

30 mm corners (fixing with self-tap-

ping screws

I. Shipping details

– Dimensions : 162 x 178 x 115 mm
– Package : 225 x 225 x 220 mm
– Weight : ca. 2,5 kg

J. Safety and security

– Data protection : EEPROM memory
– Interference test : According IEC 801
– Power down : No affect, reset to measurement

2. TECHNICAL SPECIFICATIONS

IM 12B6C2-E-H

2

IM 12B6C2-E-H

2-2. Functional description

The EXA PH200 is a real time micro-control­ler operated pH analysing system. It uses a
dedicated micro-controller with exclusively
developed software to control all functions
necessary in such a system. The input and
output functions are concentrated in the
analogue section of the instrument. Even
these functions are operated through special
interfaces designed to give a minimum of
interference problems to the digital func­tions. The digital and logic functions are
designed to operate securely. The unique
FAIL-function can give a warning when the
micro-controller has found a fault in the
measuring loop. This is accomplished by
sending a discrete 22 mA signal on the out­put. The micro-controller checks the working
of the analogue to digital input converter cir­cuit and watches over the conversion to the
output signals. By using non-volatile memory
(EEPROM) for the essential in formation the
operating parameters are fixed in memory
without the need for a battery. The software
is designed with the user in mind. It uses a
simple step by step, question and answer
style to communicate with the operator by
giving messages on the second line of the
display and indicating which keys are to be
pressed in the display too.

The user-interface is limited to a basic set of
6 keys accessible through the flexible win­dow cover. The keys are scanned conti­nuously and actions are taken immediately.
An extensive system of checking va lues and
parameters is implemented in the software .
The 2-wire design gives maximum flexibility
of operation with other industrial instruments
and controlling systems. An intrinsically safe
version is available for hazardous areas. The
rugged housing is designed for outdoor use
(IP65). In addition it is shaped in a way that
indoor panel mounting is also possible. The
optional universal mounting kit includes
brackets for all mounting methods. The
commissioning of the instrument can be
performed on site or in advance. A three
level operating system keeps the approach
clear and distinguishes between every day
operation and maintenance against one time
operations like commissioning or fine-tuning.
All this makes the EXA PH200 operate like a
normal analogue transmitter with a number
of additional functions.

These extra functions are only possible by
using a micro-controller at the heart of the
system:

• Sensor checking durig measurement (1)

• Simplified calibration through a semi­automatic sequence.

• Additional process temperature compen­sation can be activated.

• Simple range adaptation making it a ver­satile instrument.

• Wide selection of temperature sensors.

• A HOLD-function for the output.

• Three buffer tables can be programmed.

• Programmable isothermal point of inter­section.

• Protection against unauthorized access
by a passcode.

(1) European patent No. 0241601

US patent No. 4777444

3

3. INSTALLATION AND WIRING

IM 12B6C2-E-H

3-1. Installation and dimensions

3-1-1. Installation site

As the transmitter is a rain-tight type it can
be installed outdoors as well as indoors. It
should, however, be installed as close as
possible to the sensors avoiding long cable
lengths between sensors and transmitter.
The certified version can be installed in
Zone 1.
Select an installation site where:

- mechanical vibrations and shocks are
negligible;

- no relay/power switches are in the direct
environment;

- the transmitter is not mounted in direct
sunlight and severe weather conditions;

- maintenance activities are possible (no
corrosive atmospheres).

The ambient temperature and humidity
should be within the limits of the specifica­tions .

3-1-2. Mounting methods

The EXA PH200 transmitter has universal
mounting possibilities:

- panel mounting using selftapping screws

- surface mounting on a plate (by bolts
from the back)

- wall mounting on a bracket (e.g. thick
brick wall);

- pipe mounting using a bracket on a hori­zontal or vertical pipe (maximum diame­ter 50 mm).

4

Panel mounting

Surface mounting

DimensionsCut-outs for panel mounting

2 x M6 (Screws)

Unit: mm (“)Unit: mm (“)

154 (6.06`)

162 (6.4)

180 (7)

77

115 (4.5)

30 1.2)

30 (1.18)

172(6.77)

2x ø4

min. 203 (8)

min. 229 (9)

IM 12B6C2-E-H

5

Option /M: Universal wall/pipe mounting kit

Pipe mounting
(vertical)

Pipe mounting
(horizontal)

2” Pipe

2” Pipe

Wall mounting

115

(4.53)

70 (2.75)

56 (2.2)

200

(7.87)

2x ø6.6

(0.26)

4x ø10

(0.4)

77 (3.03)

IM 12B6C2-E-H

3-2. Wiring of sensors

3-2-1. General precautions

Generally, transmission of signals from pH
sensors is at a very low voltage and high
impedance level. Thus a lot of care must be
taken to avoid interference. Before connec­ting sensor cables to the transmitter make
sure that next conditions are met:
– the sensor cables are not mounted in

tracks together with high voltage and or
power switching cables

– only standard coaxial electrode cables or

extension cable are used

– the transmitter is mounted within the dis-

tance of the sensor cables (max. 10 m)

– the setup is kept flexible for easy inser-

tion and retraction of the sensors in the
fitting.

3-2-2. Additional precautions for instal-

lations in hazardous areas

Make sure that the total of capacitances and
inductances connected to the input termi­nals of the EXA PH200 do not exceed the
limits given in the certificate.
This sets a limit to the cable and extensions
used.
– Grounding:

• If the sensors are mounted in a grounded
fitting, the external earth connection on
the left hand side of the transmitter must
be connected to "protective" earth.

• If the sensors are mounted in a fitting iso­lated to ground, it is recommended (not
required) to connect the earth connection
on the left hand side of the transmitter to
"protective" earth.

– The intrinsic safe version of the EXA

PH200 instrument can be erected in
Zone 1.

– The sensors can be installed in Zone 0 or

Zone 1 if a safety barrier according to the
limits given in the system certificate is
used.

3-2-3. Liquid earth

In all circumstances, the sensor side of the
measuring loop must be grounded to the
measuring liquid. The EXA PH200 uses
advanced differential high impedance input
circuits. This technique calls for a grounding
to the liquid. In addition to that the sensor
checking circuits also use the liquid earth for
measurement of impedance of the sensors.
All Yokogawa fittings have provisions for this
connection. It is usually called liquid earth in
all our manuals.
A separate connection should be made to
the terminal numbered 14 in all cases to get
a proper and stable measuring loop.

3-2-4. Access to terminal and cable

entry

1. To access terminals remove the front
cover of the EXA PH200 by releasing the
4 captive screws.

2. Thread the sensor cables into the con­nection space and connect the cables to
the terminals as indicated in the wiring
diagram. Make sure all connections are
firm and do not touch each other.

3. Screw the gland securely and tighten it to
keep out moisture. DO NOT use a
wrench to tighten the nut.

4. The optional hose connection is used to
guide the cables coming from an immer­sion fitting through a protective plastic
tubing to the transmitter.

6

IM 12B6C2-E-H

7

3-2-5. Connection diagram for sensors

+

-

G 11 12 14 13 17 15

16

Rd Bl Rd Bl Rd

Bl

+

-

G 11 12 14 13 17 15

16

Rd Bl Wt RdBl

+

-

G 11 12 14 13 17 15

16

+

-

G 11 12 14 13 17 15

16

T

1

T

2

SE RE GE S

Rd=Red, Bl=Blue, Wt=White,

Single electrodes

Temperature Combined

Liquid earth

Temperature - Reference pH
Pt 100 AgCl glass
(Pt 1000) (other) (other)

EXA compact and retractable electrodes

pH∑ Combined electrode

Combined electrodes

Liquid earth

Connect the numbered cable leads to the
corresponding terminals

IM 12B6C2-E-H

3-3. Wiring of power supply

3-3-1. General precautions

Do not activate the power supply yet. First
make sure that the DC-power supply is
according to the specifications given.

WARNING: DO NOT USE ALTERNATING
CURRENT OR MAINS POWER SUPPLY! !

The cable leading to the distributor (power
supply) or safety barrier transports power to
and output signal from the transmitter. Use a
two conductor shielded cable with a size of
at least l.25 mm

2

and an outside diameter of
9 to 15 mm. The cable gland supplied with
the instrument accepts these diameters. The
maximum length of the cable is 2000 metre.
This ensures the minimum operating voltage
for the instrument.

3-3-2. Additional precautions for instal-

lation in hazardous areas

1. Ensure that the total of capacitances and
inductances connected to the terminals
of the EXA PH200 do not exceed the
limits given in the certificate of the safety
barrier or distributor.

2. The cable used should preferably have a
BLUE colour or marking on the outside.

3. Grounding:

• If the transmitter is mounted on a

grounded surface (e.g. a metal frame
fixed in the soil) the shield of the 2-wire
cable may NOT be connected to
ground at the distributor.

• If the transmitter is mounted on a non-

conducting surface (e.g. a brick wall) it
is recommended to ground the shield
of the 2-wire cable at the distributor
end.

4. Installation for EEx ia (sensors in Zone 0
or 1):
Generally, the distributor with input/out­put isolation has no external earth con­nection. If there is an earth connection on
the distributor and the external connec­tion of the transmitter is connected to
"protective" earth, the shield of the 2-wire
cable may NOT be connected to "protec­tive" earth at the distributor too.

3-3-3. Connection of the power supply

The terminal strip is accessed as was
described in § 3-2-4. Use the left-hand
gland to insert the 2-wire cable to the trans­mitter. Connect the supply to the terminals
mar ked +, - and G as is indicated in the
figures on pages 9 & 10.

3-3-4. Switching the instrument on

After all connections are made and checked,
the power can be switched on from the dis­tributor. Observe the correct activation of the
instrument at the display. If for any reason
the display does not indicate a value, con­sult the trouble shooting section.

8

IM 12B6C2-E-H

Dependance of load to supply voltage

9

Wiring diagrams for power supply

General purpose design
pH-transmitter
EXA PH200G

Sensor

Distributor

Output

Supply

NOTE:
The outside earth terminal should be connected to site ground by a large area conductor (e.g. a flat earth strip) for
best protection against interference.

1200

1000

800

600

400

200

0

1718 20 24 40

Ohm

550

Supply voltage (V)

Load resistance (Ω)

+
–

+
–

G

Wiring diagrams for hazardous areas

IM 12B6C2-E-H

10

Intrinsically safe design
(CELENEC standard EEX ib [ia] IIC T4)
pH-transmitter
EXA PH200S

Intrinsically safe design
(CELENEC standard EEX ib [ia] IIC T4)
pH-transmitter
EXA PH200S

EEx ib
Certified safety barrier

EEx ib
Certified distributor with
input/output isolation

Electronic current
limiting barrier
Vmax: 31.5 V
lmax: 35 mA
Pmax: 1,1 W
Zenerbarrier with
resistor
Vmax: 28 V
lmax: 93.3 mA
Pmax: 0.66 W

Shunt zener barrier or
supply unit or
isolated repeater
Vmax: 22 V
Imax: 85 mA

Sensor

Distributor

Output

Supply

Sensor

Output

Supply

Protective earthProtective earth

Protective earth

Hazardous area Safe area

Zone 0 or 1 Zone 1

Hazardous area Safe area

Zone 0 or 1 Zone 1

+
–

+
–

G

+
–

+
–

G

IM 12B6C2-E-H

4-1. Operations overview

NOTE: All 3 levels can be separately protected by a password (see §7-13).

11

4. COMMISSIONING

Routine Use Chapter

MAINTENANCE AUT.CAL Calibration with buffer solutions 5-1
Operation by keys through MAN.CAL Calibration in process 5-2
closed cover DISPLAY Show or fix additional values 5-3

TEMP Select automatic or manual

temperature compensation 5-4

HOLD Switch HOLD-function on/off 5-5

COMMISSIONING OUTPUT Adjusting the output function 4-2
Operation by *-key when SET HOLD Activating the HOLD-function 4-3
cover is removed

SERVICE SERVICE Finetuning the performance 7
Operation by coded entry
from commissioning

1. Access output

Remove cover by releasing 4 screws.

Access to commissioning menu

Select output function

Select OUTP
Confirm selection

2. Adjust low span value

Display will show *4 mA
Adjust value for low span

Select digit to adjust

Adjust digit
Confirm adjusted value

3. Adjust high span value

Display will show *20 mA
Adjust value for high span

Select digit to adjust

Adjust digit
Confirm adjusted value
Return to measurement

4-2. Output range adjustment

YES

ENT

>

^

ENT

MODE

>

^

NO

IM 12B6C2-E-H

12

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

x

MODE

OUTPUT
SET HOLD
SERVICE

YES

NO

YES

NO

MODE

*

YES

NO

MODE

pH

OUTPUT
SET HOLD
SERVICE

ENT

YES

NO

MODE

OUTPUT
SET HOLD
SERVICE

ENT

IM 12B6C2-E-H

1. What is the Output-range?

The display will always show the actual value
between -1 and 15 pH.

The output range is a linear function of mA
versus pH and is fixed by two points.
As the output is fixed to 4..20 mA the two
points of the linear function have to be pro­grammed to set the range.

The factory setting is a full range of 0..14pH.
Any value between -1.. + 15 pH is accepta­ble for both points. A minimum span of 1
unit must be kept.
An error E19 will point to not acceptable
values.

NOTE:

1. The linear output signal is limited to 3.9 to

20.5 mA giving a safety area of 2.5% at
both ends.

2. Values below 3.9 or above 20.5 mA are
not related to input values and signal a
malfunction.

2. How to adjust?

EXAMPLE:
The EXA PH200 has to be programmed for
a range of 2 ... 12 pH.

Adjust 4 mA to 2.00 pH
Adjust 20 mA to 12.00 pH

The instrument will now correct its calcula­tion for the output signal accordingly.

3. Calculation example

The current to be set at the output is calcu­lated as follows:

pH - pH

min

mA = x 16 + 4

pH

max - pHmin

pH = actual value
pH

min

= value at 4 mA

pH

max

= value at 20 mA

pH

max

- pHmin = span (≥ 1 pH)

It is advisable to choose a span devisable by
10, 5 or 2 for easy reading on scales.

4. Other possibilities

Set a 22 mA signal on the output, when
FAIL is on (see §7-7).

13

4-2. Output range adjustment

4-3. Set up the HOLD-function

IM 12B6C2-E-H

1. Access to HOLD-function

Remove cover by releasing 4 screws.

Push this key to select
Commissioning mode

Select HOLD

Move pointer to SET HOLD

HOLD = HOLD-function

Confirm selection

2. Activate HOLD-function

Display shows actual status
*H.OFF = HOLD not active
*H.ON = HOLD activated

Activate (deactivate) HOLD

Changing setting
Confirm setting

*H.FIX = HOLD fixed value
*H.LST = HOLD last value

Select HOLD fixed or last

Change selection
Confirm selection

3. Select value to hold

Display shows current setting

Adjust fixed value

Select digit to adjust

Adjust value of digit
Confirm setting
Return to measurement

14

OUTPUT
SET HOLD
SERVICE

YES

NO

YES

NO

MODE

*

.

YES

ENT

>

^

NO

YES

NO

YES

NO

x

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

MODE

YES

NO

YES

NO

MODE

OUTPUT
SET HOLD
SERVICE

*

.

YES

NO

MODE

OUTPUT
SET HOLD
SERVICE

ENT

IM 12B6C2-E-H

1. What is HOLD?

HOLD is a function freezing the output signal
temporary, during normal maintenance, pre­venting all sorts of alarming situations to
occur.
Two possibilities are generally used:
a. Keeping the output at the LAST value

just before the start of maintenance. This
should be used when recording and not
controlling instruments are connected to
the output signal.

b. Keep the output at a preset FIXED value

which will not cause any of the alarms to
go off or any controlling action to be
taken. This is the preferred situation
when dealing with pH-control systems.

2. How does it work?

The HOLD-function has to be activated from
the commissioning menu before it can be
used.
The EXA PH200 will keep the output frozen
during the following events:
a. Access to the commissioning menu.
b. Access to either of the calibration modes.
c. Switching it from the maintenance menu.

HOLD is signalled in the display by a special
flag.

The operator is prompted to switch HOLD
on or off before returning to nor mal mea­surement.

3. Example

In a neutralization set-up with both acid and
base dosing systems the neutral value is pH

7.00.
Activate the HOLD function and choose the

FlXed output value.
The span was set for 2-12 pH (see §4-2).
Thus pH 7.00 = 12 mA. Adjust the preset

value for the output at 12 mA.
During maintenance the output will be at 12

mA = pH 7.00 and no acid or base will be
pumped.

4. Auto return

Hold can be de-activated after 10 minutes if
no key is pressed. To cancel this function
(see §7-9).

15

4-3. Set up the HOLD-function

IM 12B6C2-E-H

4-4. Sensor selection and diagnostics

The inputs of the EXA PH200 transmitter are
free programmable for ease of retrofit on
existing installation. Standard glass pH-elec­trodes, Ag/AgCI reference electrodes and
Pt100 sensor need no programming. If there
is a mismatch of the sensors connected a
fault will be indicated with a signal field on
the display and if activated by a 22 mA
signal.

4-4-1. Selection of measurement and

reference electrode

The EXA PH200 is preprogramed to ac-cept
industry standard glass electrodes and refe­rence electrodes. Checks for asymmetry­potential and slope are implemented during
calibration. The on-line impedance check on
both sensors is not initialized unless activa­ted from the service level §7-5. The EXA is
suitable for all type of electrodes (e.g.
Enamel, Antimony). In §7-3 the specific
Isothermal point of intersection (ITP), slope
(pH/mV) and asymmetry potential can be set
for each type of electrode.

4-4-2. Selecting a temperature sensor

The EXA PH200 has been factory set for a
Pt100 temperature sensor to DIN standards.
This will give satisfactory results when the
normal electrode cable length is used. To
correct for cable resistance it is possible to
calibrate the sensor from the service level
(zie §7-11).
The highest accuracy is obtained by using a
Pt1000 element with the EXA PH200 trans­mitter. This element gives a ten-fold increase
in resistance dependance over a Pt100 sen­sor. Setting the instrument for Pt1000 is
from the service level at §7-4.

4-4-3. Off-line calibration checks

The EXA PH200 transmitter incorporates a
checking of the asymmetry-potential after a
calibration has been performed. This is valid
for both manual or automatic calibration.
The actual value can be called up from the
display routine in the maintenance menu
(AS). A large value can indicate a poisoning
of the reference system used. If the asym­metry-potential exceeds + 120 mV or

-120 mV an error E2 will be generated.
To disable this checking see §7-5.
The EXA PH200 also checks for the slope of
the pH sensor after automatic calibration
has been performed. The actual value of the
slope can be called up from the display rou­tine in the maintenance menu (SL). The
value is an indication for the "ageing" of the
sensor. If the value stays within the limits of
70 to 110 % of the theoretical value of

59.16 mV/pH at 25°C it is accepted.
Otherwise an error E3 is generated. Disable
this testing from the service level §7-5.

16

IM 12B6C2-E-H

4-4-4. On-line impedance checks

The EXA PH200 transmitter is delivered from
the factory with an impedance check disab­led. To activate this impedance checking
refer to §7-5. The impedance check works
on both measuring and reference electrode,
but not in the same way. The measuring
electrode is checked for presence of a high
impedance on the input side. An open cir­cuit is signalled by an error E5. A short cir­cuit is signalled by an error E4. The impe­dance of the reference electrode is meas­ured (RZ). The actual value (in kilo Ohm) can
be called up from the display routine in the
maintenance menu. When pH is measured
in high purity water it is necessary to adjust
the reference impedance for the low con­ductivity of the solution. In general a high
impedance value can be related to a dia­phragm clogging, fouling or non-immersion
of the sensors. If the value exceeds the limit
set an error E6 is generated. Activation and
limit setting (*IM.LMT) is done from the servi­ce level §7-5.

17

1.Access automatic calibration

AUT.CAL = Automatic calibration

Access to maintenance mode

Select automatic calibration

Move pointer to AUT.CAL
Confirm selection

2. First buffer calibration

CAL 7 = Calibrate at pH 7
Select pH value for first buffer solution

Accept displayed buffer

Select other value

Calibration can be ended *

Continue calibration with second
buffer solution
End calibration with on buffer only
(asymmetry potential only)

3. Second buffer calibration

CAL 4 = Calibrate at pH 4.
Select pH value for second buffer solution

Accept displayed buffer

Select other value

Calibration can be ended *

End calibration

Repeat calibration with first buffer
solution

5. MAINTENANCE 5-1. Automatic calibration

IM 12B6C2-E-H

18

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

pH

MODE

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

MODE

NO

YES

NO

YES

NO

YES

NO

YES

NO

YES

Insert electrodes in buffer solution. Display shows CAL and
flashes while instrument searches for stable measurement.

Display show CAL.END. Measurement is now stable.

*) The value shown on the display can deviate from the buffer value. This is fixed after calib-

ration is completed.

Insert electrodes in buffer solution. Display shows CAL and
flashes while instrument searches for stable measurement.

Display show CAL.END. Measurement is now stable.

YES NO

YES NO

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

IM 12B6C2-E-H

1. What is automatic calibration?

Automatic calibration is the usual process of
calibrating a pH measuring loop with the aid
of two buffer solutions.

The first calibration is usually at pH 7; this is
to correct the asymmetry potential of sen­sors (zero).
The second calibration is most commonly
made at pH 4. This corrects the slope of the
sensors (sensitivity) . After this two point cali­bration the instrument is accurate to the
buffers used.
The EXA PH200 gives you the freedom to
use up to three buffer-solutions you want in
any sequence you like. The buffer solutions
can be programed in memory tables.
In the automatic calibration mode the instru­ment prompts the operator for the re quired
buffer solution, checks the signal for stable
conditions and then calibrates. The new cali­bration is then checked and a warning is
given if values are unacceptable.

During calibration the output will be frozen if
HOLD was activated.

2. How does it work?

A. The instrument asks for a buffer. Accept

or change

B. The sensor is immersed and checked for

stability

C. CAL.END, Stop or move on the second

calibration
D. Values acceptable or rejected.
E. After second calibration give YES to end

session.
NOTES:

1. It is not necessary to have the calibration

points within the measuring range of the

instrument, it is however advisable to do

so.

2. If no keys are pressed for 10 minutes

and the calibration was not finished the

instrument will return to measurement

with the old calibration values.

3. If HOLD was activated the instrument will

return to measurement after another 10

minutes.
Press YES to start the calibration. After sta-

bilization CAL.END will show. Press NO to
move on to pH 4.

3. Example

Standard calibration procedure.
Select AUT.CAL routine using MODE and
YES keys (enter pass code if necessary).
Select buffer pH 7using YES key.

Insert the rinsed sensors from the process
into a solution of pH 7.00 at 25°C.
CAL.END display on stable reading. Press
YES to end or NO to go on to next buffer.

Clean the sensor with water and insert into
buffer solution of pH 4.00 at 25°C.
CAL.END display on stable reading. Press
YES to end.

The whole process will not take more than
15 minutes and should be repeated at least
once every 2 months or whenever the EXA
PH200 signals a malfunction with an
ERROR-message .

4. Further possibilities

- Other buffer solutions than after 4, 7, 9.

- Using Special buffer tables for temperature
compensation (e.g. calibration in warm
buffers) §7-10.

19

5-1. Automatic calibration

5-2. Manual calibration

IM 12B6C2-E-H

1. Access to manual calibration

MAN.CAL = Manual calibration

Access to maintenance mode

Select manual calibration

Move pointer to MAN.CAL
Confirm selection

2. Adjust value manually

Display shows measured value
START = Start manual calibration

Confirm start of adjustment (dis­play frozen, ready for adjustment

to new value)
Adjust new value.
Adjust process value to previously determi­ned value (e.g. from hand-held pH-meter)

Select digit to adjust

Adjust value

Confirm adjusted value

3. End calibration

CAL.END = End of calibration
End calibration

End calibration and return to
measurement
Continue routine to calibrate
second point when using buffer
solution (repeat step 2)

Error E02 or E19 indicate manual calibration
is not acceptable

20

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

E

ESCAPE TO MEASURE can be used at any stage to abort operation.

WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

MODE

NO

YES

YES

ENT

>

^

YES

NO

YES NO

YES NO

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

MEASUR
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES

YES

NO

.

NO

MODE

IM 12B6C2-E-H

1. What is manual calibration?

Manual calibration or process calibration is
the calibration executed with a freshly taken
sample from the process.

This sample is then measured with an off
line instrument and the value obtained is
programmed into the EXA PH200 transmit­ter.
Manual calibration can be used for calibra­ting the sensors with a buffer solution spe­cially made for this purpose.

NOTE:
This routine can also be used to calibrate
with two points as an alternative to automa­tic calibration e.g. for occasional use of not
programed buffers.

2. How does it work?

1. Take a sample from the process.

2. Measure the pH with an off-line pH meter
which has been previously calibrated with
standard buffers and is equiped with an
automatic temperature compensation.

3. Adjust the value of the in-line EXA PH200
transmitter to the measured value.

4. Any values outside the normal operating
range of the instrument are signal led by
Error 19.

3. Example

The EXA PH200 indicates a process value of
pH 6.54 at 50°C.

A freshly calibrated portable pH-meter inser­ted into a hot sample reads 6.62 pH at
50°C.

The value is adjusted to the process value at
manual calibration to bring the values in
agreement.

A laboratory check of the same sample
shows the value to be pH 6.612 at 25°C.

The difference is due to the change of pH of
this particular sample with temperature.

21

5-2. Manual calibration

1. Access display routine

DISP = Display routine

Access to maintenance mode

Select display

Move pointer to DISPLAY
Confirm selection

2. Read data

The second line of the display will show the
possibilities

Parameter Unit

Temperature °C
Output signal mA

Potential mV
AS Asymmetry mV
SL Slope %
RZ Impedance Ref. electrode kΩ
REL Software release

3. Reprogram data display

Move to desired value for diaplay

Confirm selection
Return to measurement

IM 12B6C2-E-H

22

5-3. Selecting a value to display

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

MODE

NO

YES

NO
YES

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

MODE

YES NO

YES NO

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

IM 12B6C2-E-H

1. What is the display routine?

The second line in the display is intended to
be used to:
– show actual status
– show messages
– show errors

When delivered from the factory the EXA
PH200 shows the temperature on the
second line.

You can make the instrument show a diffe­rent parameter on the second line by selec­ting it from the list at the right.

2. What can you read?

Temperature actual value
Output signal actual value
Potential actual value
Asymmetry measured value
Slope measured value
Impedance actual value

Reference impedance is an actual value.
The choice of temperature units is done

from the Service level.
Reference impendance is shown to indicate

the status of the diaphragm of the reference
electrode. Glass electrode impedance is also
checked but not shown.

The release version is an indication for the
servicing of the instrument and cannot be
fixed in the display.

3. Example

To check the value of the output signal
(4...20 mA) it is displayed on the second
line.

Measuring range 2 - 12 pH
Ouptut signal 4 - 20 mA

Process value 8.5 pH
Output value 4.4 mA

When the second line is changed to display
output the current signal is visible all the
time.

Whenever HOLD is activated the value on
the display is frozen to the programmed
value (using the FIXED setting).

Pressing MODE will take you back to
measuring and the temperature will show
again.

4. Further possibilities

0.01 pH/0.1 pH display resolution.
(See §7-6).

23

5-3. Selecting a value to display

5-4. Temperature compensation

IM 12B6C2-E-H

1. Access temperature compensation

TEMP = Temperature compensation

Access to maintenance mode

Select temperature compensation

Move pointer to TEMP
Confirm selection

2. Select automatic or manual temperatu­re compensation

T.AUTO = Automatic temperature compen-

sation

T.MAN = Manual temperature compensa-

tion

Select automatic/manual compensation

Change displayed selection
Confirm selection

Adjustment of temperature
Only when manual is selected

Select digit to adjust
Adjust value
Confirm adjusted value

3. Setting the temperature coefficient *

COEFF = Temperature coefficient

pH change per 10°C

When the additional process compensation
has been commissioned from the service
level this menu will show.

Adjust solution temperature compensation

Select digit to adjust
Adjust value
Confirm adjusted value

* (only when process compensation was

activated in §7-3)

24

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

MODE

NO

YES

NO

YES

ENT

>
^

ENT

>
^

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

YES NO

YES NO

MODE

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.

ENT

HOLD

YES NO

MODE

IM 12B6C2-E-H

1. What is compensated for?

Temperature influences the sensitivity of the
glass electrode.

To nullify this effect the EXA PH200 has to
compensate the pH value with the formula
derived by Nernst.

To be able to do this the temperature has to
be measured as well. Either by a seperate
sensor or a temperature setting.

Temperature compensation can be set to
manual if the process is near pH 7 or at
fixed temperature.

2. How is it compensated?

The process temperature is measured with a
separate circuit connected to the temperatu­re sensor (e.g. Pt1000 resis tor).

The resistance value of the temperature sen­sor is calculated into the temperature value.

This value is used to calculate the compen­sated value for the pH on the display.

3. Example

Setting the manual temperature compen
sation to a fixed setting of 30°C.

Press NO to change from default automatic
compensation to manual compensation.

The display will show TEMP °C and the
value can be adjusted to 30°C. Press ENT
to confirm the setting.

The display will show TEMP.MAN at the top
to indicate your choice.

4. Further Options

- Process temperature compensation (see
Service settings §7-3).

- Calibrating the temperature circuit (see
Service settings § 7-11).

25

5-4. Temperature compensation

5-5. Hold output function

IM 12B6C2-E-H

1. Access HOLD

NOTE:
This function can only be used if activated
during commissioning (see §4-3).

Access to maintenance mode

Select HOLD function

Move pointer to HOLD

Select HOLD

2. Switch HOLD on/off

Display will blink HOLD and YES/NO

Switch off HOLD function
Switch on HOLD function

HOLD in left top of display is switched

26

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

MODE

NO

YES

NO

YES

MEASURE
AUT.CAL
MAN.CAL
DISPLAY
TEMP.
HOLD

YES NO

YES NO

MODE

IM 12B6C2-E-H

1. What is HOLD?

Hold is a function which freezes the output
signal temporarily, it is normally used during
maintenance when the sensor is removed
from the measured solution to prevent
unwanted controller reaction.

The HOLD function must be commissioned
from the programming menu before it can
be switched on or off. See setup the hold
function for more details (§4-3).

2. How does it work?

From this level the HOLD function can only
be switched ON or OFF.

HOLD is switched on when you press YES
and HOLD blinks. When you press NO
HOLD is switched OFF.

A flag is kept in memory and an indication is
made in the upper left corner of the display
field.

The HOLD function only influences the out­put signal, no other functions are influenced.

The operator is prompted to switch HOLD
on or off after having performed a mainte­nance function.

3. Example

During the transfer of cleaning liquid into a
batch reactor with a pH-control system
dosing acid or alkali, the HOLD function is
switched ON to prevent the controlling in­struments from running wild.

After cleaning has ceased and the new
batch has been started HOLD is switched
OFF again and pH control resumes.

27

5-5. Hold output function

6. TROUBLE SHOOTING

IM 12B6C2-E-H

6-1. Introduction

As the EXA PH200 is a micro-processor
analyzing instrument, it performs continuous
self-checks to verify its correct working.

The error messages resulting from faults in
the working of the micro-processor system
are few. Incorrect programming by the user
can be fixed through programming with cor­rected values. See the limits given in the
respective paragraphs.

In addition to that the EXA PH200 also
checks the electrodes to establish whether
these are still functioning within the limits
implemented through the service settings.

The EXA PH200 checks the glass electrode
impedance for a low value to know if it
hasn't broken or cracked.

The reference system is prone to more dis­turbances than the glass electrode in gene­ral. The impedance is measured and com­pared to the programmed value in memory.
A high impedance signals a pollution of the
diaphragm.

Furthermore the sensors are checked at
calibration to see whether they still are reac­ting fast enough to changes in pH.

After calibration the calculated asymmetry
potential and slope are checked to see if
these are still within the limits specified in the
software. The slow shift of the asymmetry
potential could signal a poisoning of the
reference system by the process.

The decrease of slope indicates a deteriora­tion of the sensitivity of the glass electrode
or can show a coating building up at the
electrode.

The remedy for each fault is given very
shortly. Process conditions determine what
action can be taken to correct errors. As the
actual situation may vary, it is not possible
for us to give you a full solution for all cases.
If you have any problems or questions plea­se consult your nearest Yokogawa sales or
service organisation for assistance.

There is a distinction made in the weight of
errors. All errors are signalled by the FAIL
area in the display. Only errors due to faults
in the measuring circuits also result in the
activation of the FAIL function switching the
22 mA signal §7-7. These are indicated by
an asterisk (*) in the error list.

28

Code Error description Possible cause Suggested remedy

E0 Temperature of the buffer liquids is Buffer liquid is too hot Cool buffer liquid

out of range of 0 to 50 °C Bufer liquid is too cold Warm buffer liquid

E1 Measurement has not stabilized Electrodes are fouled Clean electrodes

during calibration Glass electrode too slow Use other type (faster)

Wrong type of glass electrode Use other type

E2 Calculated asymmetry potential out Calibration at pH 7 incorrect Recalibrate at pH 7

of range of -120 to +120 mV Check if buffer solution is fresh

E3 Calculated slope is out of range of Glass electrode has aged Replace glass electrode

70 to 110 % theoretical value Bad isolation on input Dry or replace cable
E4* Impedance of glass electrode too low Glass electrode cracked or broken Replace glass electrode
E5* Impedance of glass electrode too high Glass electrode coated or fouled Clean or replace glass electrode

Open circuit on measurement Check connections and cables

E6* Impedance of reference electrode too high Reference electrode fouled or clogged Clean or replace glass electrode

Liquid earth disconnected Clean or replace glass electrode
Sensors not fully immersed Check installation

E7* Measured temperature too high Process temperature too high Cool process or use sample loop

i.e. above 130 °C Wrong temperature sensor used Correct setting (§7-4)

Temperature sensor damaged Check connections and sensor

E8* Measured temperature too low Process temperature too low Warm process or use sample loop

i.e. below -10 °C Wrong temperature sensor used Correct setting (§7-4)

Short circuit in temperature input Check connections and sensor

E9* Measured value is out of pH range Temperature element broken Replace temperature sensor

of -1 to 15 pH Temperature sensor disconnected Set temperature to manual
E10* EEPROM write error Fault in electronics Try again, if not succesful call your nearest

Yokogawa office

E15 Cable resistance to temperature sensor Cable resistance too high Use Pt1000 for accurate results

exceeds 5Ω Corroded contacts Clean contacts and tighten
E17 Output inside minimum span < 1pH Incorrect programming by user Correct programming
E19 Programmed values are not accepted Incorrect programming by user Correct programming of last function
E20 All programmed values are lost Fault in electronics Call nearest Yokogawa office

Severe interference
When errors appear that are not mentionbed in this list, please consult the Yokogawa service organization. A maximum of 2 errors can be
indicated at the same time. *See §6-1.

IM 12B6C2-E-H

29

6-2. Error messages and explanation

IM 12B6C2-E-H

30

7. SERVICE MODE

7-1. Introduction

Generally speaking their is no necessity to
adjust the settings of the service section. All
parameters are pre-programmed to values
(so-called defaults) enabling you to start
working immediately.

The advanced functions available through
this section are only needed in some specific
applications. This fine-tuning of the in stru­ment gives a superior performance over
analogue 2-wire instruments.

If a function has to be adjusted it is called up
with the code mentioned. Having selected
the code then give you the possibility to eit­her activate or adjust the values for this
function. After this you will return to the entry
point to make other adjustments or go back
to the measuring status.

If errors are made during the programming
process, these will be indicated, no action
will be taken and you can start the program­ming again

Code Routine Use Chapter

01 Temperature compensation Process comp. on/off

and units Select °C or °F 7-3
02 Temperature sensors Select sensor type 7-4
03 Sensor checking Choose impedance, asymmetry

or slope 7-5
04 Display resolution Select 0,1 of 0,01 pH 7-6
05 Signalling of fail condition Switch burn-out signal 7-7
06 Stabilisation check Adjust parameters 7-8
07 Auto return function Switch on or off 7-9
08 Buffer table (7) Program user tables 7-10
09 Buffer table (4) Program user tables 7-10
10 Buffer table (9) Program user tables 7-10
11 Temperature adjustment Correct cable sensor 7-11
12 Manual adjustment ITP, slope Settings for non-standard

and asymmetry potential electrodes 7-12
33 Password activation Protecting operation levels 7-13
55 Restore default values Erase all user programmed values 7-14

IM 12B6C2-E-H

31

1. Access service

*SERV = Service settings

Access to commissioning mode

Select service function

Move pointer to SERVICE

Confirm selection

2. Enter code to slect required function

Display will show *CODE

Enter access code to select
routine

Select digit to adjust

Adjust code for entry
Confirm selection

3. Adjust setting
(see individual routines)

Select digit to adjust
Adjust value
Confirm adjusted value
Return to step 1 or
Return to measurement

7-2. Access to service settings

OUTPUT
SET HOLD
SERVICE

YES

NO

MODE

ENT

ESCAPE TO MEASURE can be used at any stage to abort operation.
WARNING: If the HOLD function is activated the instrument returns with the question HOLD (flashing); answer YES or NO or

MODE again to return to measurement.

MODE

x

NO

YES

>

ENT

^

>
^

ENT
YES

MODE

YES

YES

NO

NO

MODE

OUTPUT
SET HOLD
SERVICE

*

.

. .

YES

NO

ENT

MODE

OUTPUT
SET HOLD
SERVICE

IM 12B6C2-E-H

32

ACCESS CODE : 01 (see §7-2)
DISPLAY : *T.CODE

Adjustment : (X.X)

Explanation:
The default setting of 000 gives only Nernst
linear compensation for the sensitivity of the
sensors and an indication of temperature in
°C. The choice of automatic or manual tem­perature compensation has no influence.
Setting the code to 01 will give a tempera­ture indication in degrees Fahrenheit (°F) on
the display only. Setting the code to 10 will
activate the extra process compensation
calculation. The coefficient has to be adjus­ted from the maintenance level. Setting the
code to 11 will do the same for indication of
°F.

Default: 0.0 = European model

0.1 = US model

Process compensation factor

In general the automatic temperature com­pensation according to the Nernst equation
will be sufficient for most pH measurements.
In cases where the accuracy is critical an

extra process compensation can be activa­ted. The compensation is expressed by a
factor (

a) which can be programmed
between -1.00 to + pH per 10°C (or -0.100
to +0.100 pH per °C). To establish the cor­rect factor for your application, proceed as
follows:

1. Take a representative sample of your pro-

cess composition.

2. Measure the pH (with automatic tempe-

rature compensation to Nernst) at the
minimum actual temperature of the pro­cess. Call this pH

low

.

3. Heat the sample to the maximum tempe-

rature of the process.

4. Measure the pH. Call this pH

high

.

5. Calculate the correct factor (a) from::

(pH

high

- pH

low

)

a = – x 10

T

high

- T

low

Example : pH

high

= 8.92 at 30°C

pH

low

= 9.20 at 20°C

(8.92 – 9.20)

a = – x 10 = + 0,28

30 – 20

6. Enter this factor with the correct sign in

the temperature compensations routine

§5-4.

ACCESS CODE : 02 (see §7-2)
DISPLAY : *T.SENS

Adjustment : (X)

Explanation:
The indication here determines which tem­perature sensor is connected to the instru­ment. Check what sensor will be used in
your plant and set the correct number for it.
Yokogawa sensors are available with Pt100
or Pt1000 resistance elements. The SIGMA
PH8-ERG or PH8-EFG use the 5k1NTC­sensor.

Default : 1 = Pt100 DIN

X.X

0.X Process compensation inactive

1.X Process compensation active
X.0 Temperature in °C
X.1 Temperature in °F

X
0 Pt1000
1 Pt100 DIN
2 Japanese version
3 SIGMA Combi-electrode 5k1
4 NTC resistor 3k (Balco)

7-3. Temperature function 7-4. Temperature sensors

IM 12B6C2-E-H

33

ACCESS CODE : 03 (see §7-2)
DISPLAY : *CHECK

Adjustment : (X.X.X)

Impedance checking is for both sensors
*IM.LMT = Impedance limit in kΩ

Explanation:
The default setting of 110 has one function
disabled. Each digit controls one function;
0 = OFF; 1 = ON.

The first (left hand) digit controls the asym­metry potential checking function. This
checks whether the calculated asymmetry
after calibration is within the -120 to +120
mV range of the instrument. If not error E02
is generated.

The second (middle) digit controls the slope
checking function. This checks whether the
calculated slope after calibration is within the
limits of 70 to 110 % of the theoretical value
of 59.16 mV/pH at 25°C. If not error E03 will
be generated.

The third (right hand) digit controls the sen­sor impedance checking function. The refe­rence electrode or the reference system of a
combined electrode is checked for a high
impedance value pointing to a problem in
the measurement. Also the glass electrode
checking is switched on.

This check only indicates a broken sensor or
a wrong glass electrode type. When con­necting other than normal glass electrodes
this checking function can be switched off. If
the third digit is set to 1, the next step is to
adjust the maximum value which will trip the
error E06.

The default value of 100 kΩ is sufficient for
most sensors. The display will show
*IM.LMT meaning the impedance limit set­ting value in kΩ. Adjust to a significant value
for the reference system used and suitable
in your process.

NOTE:
See §7-12 for ITP settings out of limits

Default :1.1.0 = European model

1.1.1 = US model

Limits : Impedance

50.0 to 999.0 kΩ

X.X.X

0.X.X Asymmetry checking inactive

1.X.X Asymmetry checking active
X.0.X Slope checking inactive
X.1.X Slope checking active
X.X.0 Impedance checking inactive
X.X.1 Impedance checking active

7-5. Sensor check

IM 12B6C2-E-H

34

7-6. Display resolution

ACCESS CODE : 04 (see §7-2)
DISPLAY : *DISP

Adjustment : (X)

Explanation:
The default setting of 1 gives an indication of

0.01 pH unit on the display which is the
maximum accuracy of the instrument when
normal industrial buffer solutions are used. In
some processes the indication of the last
digit can be suppressed to give an indication
of 0.1 pH units only. The instrument will
maintain its accuracy at the same level as
before only the indication is changed!!

Default : 1 = 0.01 pH

7-7. Signalling of fail condition

ACCESS CODE : 05 (see §7-2)
DISPLAY : *BURN

Adjustment : (X)

Explanation:
Besides an indication at the display in the
field, sometimes an indication of errors in the
control room is also necessary. This is possi­ble by sending a special signal over the 2­wire connection to the receiving instrument.
A singal of 22 mA is used, because it is
outside the normal analogue range of 4 to
20 mA. If at the receiving end an alarm is set
to the value represented by 22 mA, it is
obvious that the proper action can be taken
from the control room too . The signal uses
the same convention as used in thermo­couple indication named as burn-out detec­tion.

Default : 0 = OFF

7-8. Stabilization check

ACCESS CODE : 06 (see §7-2)
DISPLAY : *iT.SEC en *iPH

Adjustment : Criteria for automatic

calibration stabilization
time and pH.

Explanation:
The criteria for deciding whether a value has
stabilized during calibration is set to a rate of

0.02 pH during 5 seconds. Depending on
the specific needs of your sensor system
this parameter can be changed.

Please keep in mind that changing both
values will not always change the criteria i.e.

0.02 pH/5 s=0.04 pH/10 s=0.10 pH/25 s
etc. If the system has not stabilized an error
E02 will be generated.

Default : 0.02 pH/5 seconds.

X
0 0.1 pH displayed
1 0.01 pH displayed

X
0 UIT
1 AAN 22 mA steady signal on fault.
2 AAN 22 mA pulse during 30 s at start

of fault then normal output.

IM 12B6C2-E-H

35

7-9. Auto return

ACCESS CODE : 07 (see §7-2)
DISPLAY : *RET

Adjustment : (X)

Automatic return to measu ring when no
keys were pus hed for 10 minutes.

Explanation:
As a safeguard against long maintenance
jobs or inadvertently pushing a button it is
possible to let the system return to its nor­mal function of measurement when no keys
are pushed for 10 minutes. When you have
activated Hold and entered a routine the
system will return to measurement after 2x
10 minutes.

Default : 1 = ON

7-10. Buffer tables

ACCESSCODE : 08, 09, 10 (see §7-2)

DISPLAY : *BUF.ID

The following tables can be changed by the

user.

Explanation:

There are 3 separate buffer tables in memo-

ry. All three tables work in the same way. As

a default all buffer tables are set to the nomi-

nal values of 7.00, 4.00 and 9.00 for all tem-

peratures between 0 and 50°C. The first

thing to do if you want to use your own

buffer tables is to program the values of

these tables. The first thing you will see is

*BUF.ID: buffer identity number. As a default

it is set to the same value as the pH used in

the table. You can change it to indicate a

change you made. After pushing ENT you

will be prompted with the first buffer value at

0°C. By choosing NO you will skip to the

next value.

By choosing YES you can adjust the value

to your wishes. The next value is 5 °C and

then on to 50 °C in 5 ° steps. Examples of

commercially available buffer solutions are

mentioned in the literature.

NOTES:

1. It is not necessary to program every sin­gle value of the table.

2. By pushing NO, values are skipped; the
system will use interpolation between
values.

3. The two digit number entered as BUF.ID
is shown in the calibration routine after

CAL....

X
0 OFF
1 ON

Servicecode 08 09 10
BUF.ID 07 04 09

0 °C 6.98 4.01 9.46

5 °C 6.95 4.01 9.39
10 °C 6.92 4.00 9.33
15 °C 6.90 4.00 9.27
20 °C 6.88 4.00 9.22
25 °C 6.86 4.01 9.18
30 °C 6.85 4.01 9.14
35 °C 6.84 4.02 9.10
40 °C 6.84 4.03 9.07
45 °C 6.83 4.04 9.04
50 °C 6.83 4.06 9.01

IM 12B6C2-E-H

36

7-11. Temperature adjustment

ACCESS CODE : 11 (see §7-2)
DISPLAY : *T.ADJ

Adjustment : Correction for cable

resistance

Explanation:
The temperature measurement is a two wire
resistance measurement. In this kind of
measurement the length of the connecting
cable can influence the accuracy of the tem­perature indication. To compensate for the
extra resistance of the cable up to 551 can
be calibrated. Connect the correct tempera­ture sensor to the EXA instrument and insert
it in a stable temperature bath of a known
value. Check the temperature indicated at
this setting in °C and adjust the value if
necessary. Now the EXA transmitter has
been calibrated to compensate for the cable
resistance.

7-12. Manual adjustment of ITP, slope

and asymmetry potential

ACCESS CODE : 12 (see §7-2)
DISPLAY : *ITP, *SLOPE, *ASPOT

Adjustment : Set the value of the

isothermal point of
intersection (ITP),
slope and asymmetry­potential.

Explanation:
The EXA PH200 can be programmed for pH
electrodes that do not have a standard ITP
(0 mV point) at pH 7.

In some applications special pH electrodes
are used (e.g. Emamel, Antimony, etc.)
which have a different construction and prin­ciple than standard electrodes. The basic
parameters of these electrodes can be pro­grammed in this section The isothermal
point of intersection (ITP) is the pH-value
where the electrode gives 0 mV. The slope is
the sensitivity of the electrode in percent of
theoretical value (59.10 mV/pH at 25°C).
The asymmetry potential is the offset in mV
of the reference system used.

Defaults : ITP = 7.00 pH

SLOPE = 100%
ASPOT = 0 mV

Limits : ITP :-1 to 15 pH

SLOPE : 70 to 110%
ASPOT : -120 to

+120 mV

With checks off:

SLOPE : 25 to 199%
ASPOT : -199 to

+199 mV

IM 12B6C2-E-H

37

7-13. Pasword protection by three digit

code

ACCESS CODE : 33 (see §7-2)
DISPLAY : *PASS

Adjustment : (X.X.X)

Explanation:
In some cases a protection of operation
levels is wanted. In this way unauthorized
access to any of the 3 levels can be blocked
by a simple password. When a password is
selected for an operation level, access to
that level can only be obtained after entering
the password. The display will show a mes­sage *PASS* to indicate the entry of the
password.

NOTE:
# can be a digit from 1 to 9, and it will give a
protection according to the schematic below
of the programmed level.

0 = No password
1 = Password is 111
2 = Password is 333
3 = Password is 777
4 = Password is 888
5 = Password is 123
6 = Password is 957
7 = Password is 331
8 = Password is 546
9 = Password is 847

NOTE:
For the Maintenance and Commissioning
level the password entry is always requested
when entering from the measure mode.
– For the Service level the password entry

is requested after pushing the YES-key

– When the Service level protection is acti-

vated, the password cannot be changed
by unauthorized persons.

Default : 0.0.0 No password protection

7-14. Restore default settings

ACCESS CODE : 55 (see §7-2)
DISPLAY : ERASE

Adjustment:
YES = Erase all programmed values and

replace them by defaults.

NO = Keep all programmed values as

before

Explanation:
This entry is provided to make it possible to
start from the default values given by
Yokogawa and thus erase all previously pro­grammed information.

X.X.X

0.X.X Protection on Maintenance level
inactive

X.0.X. Protection on Commissioning

level inactive

X.X.0 Protection on Service level

inactive

#.X.X Protection on Maintenance level

active

X.#.X Protection on Commissioning

level active

X.X.# Protection on Service level

active

WARNING

1. Do not use this code without pro­per authority as all settings and
programmed functions will be lost!!

2. Do not enter service codes that are
not mentioned in this booklet.

IM 12B6C2-E-H

38

8. CLASSIFICATION 8-1. Cenelec

Any shunt zenerdiode safety barrier or supply unit or isolated repeater certified by BASEEFA or any EEC approved certification body to
[EEx ia] IIC or [EEx ib] IIC where the output current is limited in a different way and not exceeding the follwoing characteristics:
Vmax.out = 22 V en Imax.out = 85 mA
such as (but not limited to): Type : Camille Bauer Sineax 84-2B1-511

Sineax 89-2B1-511 (P.T.B. Cert. Ex-81/2044X)

of

SYSTEM CERTIFICATE
EXA200 INSTRUMENTS
BASEEFA NR Ex 892380

A) 1 ORP-sensor,

such as (but not limited to) SM29-PT8
or
A) 1 PH-glass sensor, SM21-AG4

such as (but not limited to) SM21-AG6
plus SM21-TL4
B) 1 reference sensor SR20-AC22

such as (but not limited to) SR20-AP24
or SR20-AL32
AB) 1 combined sensor SC21-AGP24

such as (but not limited to) SC21-ASP24
plus
C) 1 temperature sensor SM60-Pt100

such as (but not limited to) SM60-Pt1000
These are all passive sensors to be regarded as “simple appara-

tus” i.e. devices which comply with clause 1.3 van EN 50014.

Ex-classification: EEx ib [ia] IIC T4
Zone 0 or 1 Zone 1

ZONE 1

OR

ZONE 2

Connecting cables
such as (but not limited to):
WU20-PC5 WU20-PC2
WU20-PC10 K1220 EM
WU-LT2

pH 200 S
Vout = 14.4 V max.
Iout = 3.6 mA max.
C ext = 1300 nF max
L ext = 1000 mH max.

BASEEFA Nr. Ex 89C2379

SC 200 S
Vout = 14.4 V max.
Iout = 72.8 mA max.
C ext = 1300 nF max
L ext = 8.0 mH max.

BASEEFA Nr. Ex 89C2379

NON HAZARDOUS AREA

Certified Barrier with electronic current limitation and the following characteristics:
Vmax.out = 31.5 V, Imax.out = 35 mA, Pmax.out = 1.1 W
Type: Yokogawa Bard 400 (BASEEFA Cert. Ex 84B2257X)

Any shunt zenerdiode safety barrier certified by BASEEFA or any EEC approved certification body to [EEx ia] IIC or [EEx ib] IIC where the
output current is limited by a resistor “R” directly in the output line such that Imax.out = Vmax.out / R and not exceeding the follwoing
characteristics:
Vmax.out = 28 V; Imax.out = 93.3 mA Pmax.out = 8.66 W.
such as (but not limited to):
Type: MTL 728

MTL 788 (BASEEFA Cert. Ex 832452)
MTL 788 R
Stahl 8981/31-280/085/00 (P.T.B. Cert. Ex-78/2007X)

of

1 conductivity sensor with SC41-SP34

integral temperature sensor SC49-FP08

such as (but not limited to) SC41-SP24

SC41-EP14
SC41-EP04

These are all passive sensors to be regarded as “simple appara­tus” i.e. devices which comply with clause 1.3 van EN 50014.

Connecting cables
such as (but not limited to):
WU40-LH18 WU40-LH2
WU40-LH5

11 12 14 13 17 15 16

11 12 14 13 17 15 16

G - +

G - +

IM 12B6C2-E-H

39

Class I, Division I, Groups ABCD
Vmax = 31.5 V
Imax = 93.3 mA
Ci = 5 µF
Li = 16.5 mH

8-2. FM

A) 1 ORP-sensor,

such as (but not limited to) SM29-PT8
or
A) 1 PH-galss sensor, SM21-AG4

such as (but not limited to) SM21-AG6
plus SM21-TL4
B) 1 reference sensor SR20-AC22

such as (but not limited to) SR20-AP24
or SR20-AL32
AB) 1 combined sensor SC21-AGP24

such as (but not limited to) SC21-ASP24
plus
C) 1 temperature sensor SM60-Pt100

such as (but not limited to) SM60-Pt1000
These are all passive sensors to be regarded as “simple appara-

tus”, i.e. devices which do neither store nor generate voltages
over 1.2 V, currents over 0.1 A, power over 25 W or energy over
20 mJ .

pH 200 S
V

out

= 14.4 V max.

I

out

= 26 mA max.

C ext = 1 µF max
L ext = 58 mH max.

SC 200 S
V

out

= 14.4 V max.

I

out

= 129 mA max.

C ext = 1 µF max
L ext = 2.3 mH max.

NON HAZARDOUS LOCATION

31.5 Vmax
4-20 mA

CONTROL DRAWING FOR EXA 200 INSTRUMENTS

HAZARDOUS LOCATION

1 conductivity sensor with SC41-SP34

integral temperature sensor SC49-FP08

such as (but not limited to) SC41-SP24

SC41-EP14
SC41-EP04

These are all passive sensors to be regarded as “simple appara­tus”, i.e. devices which do neither store nor generate voltages
over 1.2 V, currents over 0.1 A, power over 25 W or energy over
20 mJ .

Connecting cables
such as (but not limited to):
WU20-PC5 WU20-PC2
WU20-PC10 K1220 EM
WU-LT2
10 meters maximum

Connecting cables
such as (but not limited to):
WU40-LH18 WU40-LH2
WU40-LH5
10 meters maximum

FMRC-approved barrier
To be installed in accordance with ANSI/RP 12.6 and NEC requirements
Maximum safe area voltage should not exceed 250 Vrms

+

+

–

–

•

•

•

11 12 14 13 17 15 16

11 12 14 13 17 15 16

IM 12B6C2-E-H

40

9. CHANGE FROM PH TO ORP MEASUREMENT

The PH200 transmitter can be used for pH
measurement and tor ORP measurement.
The factory delivers the instnument in the pH
configuration with the possibility to change
easily to ORP.

9-1. How to change pH measurement to

ORP measurement

Remove the cover after loosening the 4
screws. Now you have access to the elec­tronics. Loosen the 4 screws that hold the
boards in place and remove them from the
enclosure. On the upper back-side of the
DlSPLAY-board there is a blue jumper
switch. Change the springjumper from the
upper contact to the lower contact and
make sure that the spring is in its locked
position to ensure good contact (see figure).

The PH200 transmitter can be reassembled
now, following the opposite sequence as de
scribed above. The next step is to reset the
memory of the transmitter. The following
simple procedure must be followed:

1. Push the key marked with *, push the NO
key 2 times till *SERV appears in the mes­sage display, push YES.

2. The display shows *CODE 00; Change
the code 00 to 55 with the arrow keys.
Confirm selection with the ENT-key.

3. The display shows ERASE and now the
YES key must be pushed.

4. The display shows *SERV. Pushing the
MODE key finishes the procedure to
measure ORP.

9-2. Commissioning the transmitter

As ORP transmitter, the PH200 has basically
the same functions as explained earlier in
this manual. While commissioning, the
microprocessor will skip its relevant settings.
Instead of pH all values and limits are
expressed in mV.

9-3. Maintenance of the transmitter

Calibration of the ORP transmitter is a one
point calibration only. Although there are
several ORP buffers available, mostly the
unit is calibrated with grab sample, analysed
on the laboratory with reference method.
Automatic temperature compensation for
ORP is not possible, so the menus AUT.CAL
and TEMP are skipped during maintenance
menu after pushing the MODE key.

9-4. Special features

In many applications the ORP readings are
dependent on the pH of the process liquid.
In many applications we can eliminate this
influence by using a pH electrode as a refe­rence electrode. Due to the high impedance
of the glass electrodes, the electrodes are
connected reverse, resulting in “ - “ readings
where nor mally “ + “ readings are expected.
This does not necessarily influence the ORP
control, since the output range is freely
selectable.

pH

ORP

IM 12B6C2-E-H

41

11
12
13
14
15
16
17

11
12
13
14
15
16
17

Reference Calomel Ag/AgCl (1 m) Ag/AgCl (3m) Ag/AgCl (verz.) pH glass
ORP BUFFER MEDIUM
Saturated in 1.68 pH 356 364 393 401 ± 50
Chinhydron in 4.0 pH 218 226 255 263 ± 50

in 6.86 pH 49 57 86 94 ± 50

in 9.18 pH -87 -79 -50 -42 ± 50
Saturated
Hydrochinon in 6.86 pH -50 -42 -13 -5 ± -50
ZoBell
solution 187 195 225 232

NOTE: all values at 25 °C and tolerance +/- 20 mV

9-6. Buffer values

11
12
13
14
15
16
17

11
12
13
14
15
16
17

11
12
13
14
15
16
17

Temperature
Temperature
Reference
Liquid earth
Metal (measure)
Shield
Shield

Cable marker

T1 Temperature
T2 Temperature
RE Reference
SE Liquid earth
GE (Measure)

T1 Temperature
T2 Temperature
RE Reference
SE Liquid earth
GE (Measureg)

Red

Black

Red

Blue

Blue

Blue

Red

White

Green
Yellow
Black

Red

ORP/PH-WIRING

ORP/REF-WIRING

Green
Yellow
Red

Transp.

Blue

Yellow

Red

ORP-TRANSMITTER

Combined
ORP/pH-electrode

Separate electrodes

ORP/REF Elektroden

NOTE: reverse mV reading

9-5. Wiring diagram

IM 12B6C2-E-H

42

APPENDIX A

Software version 3.0 compared to ver­sions 1 and 2*.

In 1994 the software of EXA PH200 has
undergone a major update as result of user
feed back. New features are made accessi­ble by additional Service Codes to avoid
programming conflicts with users of previous
versions.

The new features are:
9-1. Call for maintenance

CODE : 13
DISPLAY : *CALL.M

Adjustment: (X)

If “1” is selected, the period can be adjusted in
days between 1 and 250.
Default: 60

Explanation:
Company policy may require scheduled
maintenance for pH transmitters. This func
tion will alert the user that the time has
come to perform the scheduled maintenan­ce. This becomes visible on the display by
E16 FAIL message. This is one of the advan­ced diagnostic features of the pH200 trans­mitter.

Default: 0

2. Setting limits of asymmetry

CODE : 14
DISPLAY : *ASLOW

Adjustment : Set the maximum de-

viation from theoretical
zero point. Both
deviations AS.LOW(-)
and AS.HIG(+) are set
in dependently.
Adjustment can be
achieved after activa­ting in access-code

03.

Explanation:
Most sensors have theoretical 0 mV at 7 pH.
Actually these sensors have some off set
voltage which is called 'asymmetry poten­tial'. During calibration EXA corrects this
asymmetry potential. The value of the asym­metry potential is an indicator of the condi­tion of the sensor. Therefore EXA allows the
user to finetune this important diagnostic
tool. Exceeding the programmed value gives
E2 immediately after calibration.

Default : -1 20mV

+120 mV

3. Setting limits of slope

CODE : 15
DISPLAY : *SL.LOW

Adjustment : The user is prompted

to adjust the maxi­mum deviation from
the theoretical sensiti­vity of a sensor (59.16
mV at 25 °C.
Both deviations
SL.LOW (-) and
SL.HIG (+) are set in
dependently.
Adjustment can be
achieved after activa­ting in access-code

03.

Explanation:
pH sensors follow the Nernst equation. How
ever, aged or contaminated sensors will
show a loss of sensitivity. This sensitivity can
be expressed in % of the theoretical value
and is then called 'slope'. To prevent the
user from calibrating a bad sensor, EXA will
display E3 immediately after calibration if the
calculated slope exceeds these limits.

Default : 70% low

110% high

X
0 Not active
1 Active

IM 12B6C2-E-H

43

4. Selection of "soft" or "hard" FAIL
signalling

CODE : 16
DISPLAY : *ERR.01

Adjustment:
NO : Error 01 is skipped. Next error is

shown

YES : 0 = “soft” alarm

1 = “hard” alarm

Pressing “ENT" confirms the selection.
Explanation:

The self-diagnostics monitor the condition of
sensor and transmitter. Some troubles are
less severe than other. EXA allows the user
to choose between a "call for maintenance”
and a "system failure”. If soft alarm action is
selected, the FAIL message flag is flashing.
The output functions will not go into “BURN­OUT” position.

If hard alarm function is selected the output
goes into *BURN-OUT* signal. If program­med that way in service code 30. The FAIL
flag is shown in the display and the contact
functions are no longer active.

Defaults:
See "Error messages and explanation
(Chapter 6-2).

5. New defaults

CODE : 03
Adjustment : 1.1.1

CODE : 08, 09, 10
Adjustment : NIST Buffers

(formerly NBS)

6. New display messages

E14 : No valid calibration

The transmitter has
been switched from
pH to ORP. Reset
memory with code 55.

E16 : Call for maintenance

The MTBM is expired;
cali bration is needed.

IM 12B6C2-E-H
Subject to change without notice
Copyright ©

Printed in The Netherlands, 06-707 (A) Q

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