Honeywell HPB, HPA User Manual

Honeywell Precision Barometer

HPB & HPA

ADS-14071 5/02 Solid State Electronics Center

Users Manual

Version H2.4

ADS-14071 Rev. 5/02

Customer Service Representative
[phone] fax: [phone]
E-Mail: [e-mail]
Web Site: www.ssec.honeywell.com

No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying and recording, for any purpose, without the express written permission of Honeywell, Inc.
Honeywell reserves the right to make changes to any products or technology herein to improve reliability, function
or design. Honeywell does not assume any liability arising out of the application or use of any product or circuit
described herein; neither does it convey any license under its patent rights nor the rights of others.

©Copyright 2001 Honeywell Inc., All rights reserved. Printed in U.S.A.

Table of Contents

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Hardware Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.0 GETTING STARTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.2 Equipment Needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.3 Terminal Program Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2.4 Initial Turn-On Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.5 Command Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.6 Step-By-Step Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.7 Command Functional Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.0 COMMANDS - QUICK REFERENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.0 FUNCTIONAL OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.2 What Is Integration? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.3 Pressure Reading Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.4 Customized Pressure Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.5 Command Illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.6 Pressure Reading Decimal Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.7 HPB Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.0 COMMANDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.1 Command Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.2 Information Request Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.3 Action Directing Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.4 Command RepliesGeneral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.5 ASCII Format Replies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.6 Binary Format Replies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5.7 Command And Reply Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

5.8 Command Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.9 Command Summary Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

5.10 Command Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6.0 ELECTRICAL CONNECTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

7.0 TIMING DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

8.0 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

9.0 DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

i

Figures

Figure 1. HPB Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 2. Pressure Reading Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 3. Custom Slope (X=) Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 4. Custom Offset (Z=) Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 5. Integration (I=) Command, Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 6. Integration (I=) Command, Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 7a. Deadband and Sensitivity (DS) Command Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 7b. Deadband and Sensitivity (DS) Command Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 8. Idle Count (IC) Command Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 9. Synchronize Integration Cycles (SI) Command Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 10. HPB Ring Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 11. HPB Multi-drop Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 12. Single HPB Command and Reply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 13. Multiple HPB Network Command and Replies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 14. HPB Electrical Connector Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Figure 15. Connection to a Host Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Figure 16. Default Single Pressure Reading Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Figure 17. Default Continuous Pressure Reading Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Figure 18. Continuous Pressure (with IC = 1) Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Figure 19. Timing Diagram for 20 Readings Per Second . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Figure 20. Timing Diagram for 50 Readings Per Second . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Figure 21. Timing Diagram for 120 Readings Per Second . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Figure 22. HPB Case Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Figure 23. Electrical Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

ii

Tables

Table 1. Decimal Place Locations for Pressure Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 2. Header Description for Binary Format Pressure Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 3. Binary Format Character Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 4. Command List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 5. Command Factory Default List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 6. Display Units Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Table 7. Transmission Times at Selected Baud Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Table 8. Number of bytes in Various Replies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Table 9. ASCII Conversion Table, Decimal to Hexadecimal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Table 10. RS-232 Standard Pin Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

iii

1.0 INTRODUCTION

1.1 Product Overview

The Honeywell Precision Barometer* (HPB) provides high accuracy absolute pressure readings in digital form. The
first-time user will be able to use the HPB within minutes, yet capability exists to configure the HPB for optimum
performance in specific applications.

The heart of the HPB measuring system is a silicon piezoresistive sensor, which contains both pressure and
temperature-sensitive elements. Digital signals representing temperature and pressure are processed by a
microprocessor to produce fully temperature compensated and calibrated pressure readings over the entire -40 to
85°C temperature range.

The HPB receives commands and sends data in either a ring or a multidrop TTL-Level configuration. Using an RS232­to-TTL converter, up to 89 units can be connected in a ring or multi-drop configuration to a single serial port of a
computer. Group (multicast) addressing allows up to nine groups of HPBs to be addressed with a single
command. Global (broadcast) addressing will send a command to all HPBs on the bus.

Any computer having a serial port, terminal emulation software and a RS232-to-TTL converter can be connected to
the HPB to allow the user to select baud rates, sample rates, readout resolution, units of pressure and other choices.

User selected functions are set through the digital interface. The selected functions may either be used temporarily,
until the HPB is powered down, or may be stored in the internal EEPROM to automatically configure the HPB each
time power is applied.

The HPB is a low power device. It can be configured to enter a micropower shut down mode with a simple command
or by switching the state of power control line, see the OP command in section 5.10 for details. For buoy
applications, the HPB has a wave filtering routine to make data acquisition easier. See the DO command in section

5.10 for details.

1.2 Hardware Description

See Sections 8 and 9.

* For simplicity, references thoughout this manual to both HPB & HPA have been shortened to HPB.

1

2. 0 GETTING STARTED

2.1 Overview

The first-time user should approach the HPB in a manner analogous to using a word processor program; i.e., many
features are available but one may begin by using those of interest at the moment. Section 2.7 of this manual lists
command features by functional groups to assist in this selection. When shipped from the factory, the default
settings provide a pressure transducer that will be usable for many applications. Feel free to make command-driven
configuration changes as you become familiar with the HPB. Default parameters are restored when the power is
cycled. Once the user is familiar with the performance and command structure, changes may be made and stored
using the Store Parameters (SP) command. Once stored, the new default settings are activated each time the HPB is
powered up. This tailors the personality of the HPB to meet the needs of a particular application.

2.2 Equipment Needed

To prepare the HPB for operation, several items are needed:

 A mating connector with proper wiring connections (see connector part number and wiring diagram in Section 6-

Electrical Connections);

 A DC power supply;

 A pressure source;

 A computer, or host processor, having an RS-232 serial port and terminal program software such as PROCOMMTM,

VERSATERMTM, TERMINAL (Windows® 3.x) or HYPERTERMINAL (Windows® 95). These programs are normally
used to interface to a modem. The wiring diagram designates which HPB pins must connect to the computer
send, receive and common pins for proper communications. Some computers may not have an RS-232 serial
port connection identical to the one shown in Section 6, making it necessary to adapt the HPB connections to that
particular computer.

 An RS232-to-TTL converter

2.3 Terminal Program Settings

 Enter the following settings in the terminal program:

Baud Rate.............................................................9600

Start Bits......................................................................1

Data Bits......................................................................8

Stop Bits......................................................................1

Parity....................................................................None

 Attach a line feed to the incoming carriage return <CR>.

 Turn the local echo ON.

When shipped from the factory, the HPB is set to a baud rate of 9600, 1 start bit, 8 data bits with no parity and
one stop bit. If the baud rate has been subsequently changed, and is unknown, it will be necessary to search all
baud rate values to reestablish communication. See the BP command description in Section 5.10 of this manual
for possible settings.

2

2.4 Initial Turn-on Response

Digital Output

Once the wiring connections and terminal program settings are complete, the HPB will automatically send the
following response (or similar to) when power is applied. This reply will be generated any time power is applied to
the HPB.

Typical Reply:

?01HPB_ _ 1200HPAa ring network configuration
?00HPB_ _1200HPAa multi-drop network configuration

The ?01 or ?00 indicates a default address device called a null address. This HPB has not yet been assigned
an ID number so it assumes the null address.

2.5 Command Format

Any command interaction with the HPB requires electrical connection to the TTL serial communications pins.
There are two basic types of commands  action directing commands and information requesting commands.
Theses are described in Commands  Section 5

Typical HPB commands have the form *ddcc = nnn <cr>

Where: * is the command header character

dd is the decimal address of the HPB
cc is a command (refer to Commands  Section 5 for a complete description of commands)
= equal sign (required in some commands)
nnn additional characters (required in some commands)
<cr> carriage return is required to end all commands

(do not type, press the ENTER/RETURN key)

2.6 Step-by-Step Examples (Only for single HPB connection)

 READ SINGLE PRESSURE

Once the HPB is powered up and connected to a computer, enter the following command:

Type: *00P1 <cr> Response: ?01CP=15.458 (ring)

Where: * indicates the start of a command

00 is the null address of the HPB (see note below)
P1 is the command to read the most current pressure

Note: The ? indicates a response from a null address HPB  one which has not been assigned a device ID. A

null address, 00, is coded into each HPB at the factory. When a ring networked null address HPB
responds, it adds one to its address, hence, the response 01. Refer to the ID command in Section 5.10
for a description of addresses and responses.

In the reply, the 01 identifies the individual unit address (range 01-89). The CP=15.458 indicates
a compensated pressure of 15.458 psi. Your unit may not show this specific reading, depending on the
applied pressure it is measuring.

?00CP=15.458 (multi-drop)

3

 SET DEVICE ID

To give the HPB an assigned address of 01 up to 89, enter the following commands (Assumes the HPB is still null­addressed):

Type: *00WE <cr> This enables the HPB to change a parameter in RAM

Type: *00ID=01 <cr> This sets the null addressed HPB to device ID=01.

Note: The device ID is now used in the command input

Type: *01S= <cr> Response: #01S=00052036 (serial number test)

The # now replaces the ? in the header and indicates the HPB response is from an address assigned unit.

Where: * indicates the start of a command

00 is the null address of the HPB
WE is the command to enable a configuration parameter change
ID is the command to change the device address
01 is the assigned HPB address for this example
S= is the command to read the serial number

 READ PRODUCTION DATE

To read the production date, enter the following command:

Type: *01P= <cr> Response: #01P=09/26/00

 READ CONTINUOUS PRESSURE

For continuous pressure readings at the factory set default rate of 5 per second, enter the following command:

Type: *01P2 <cr> This enables a continuous stream of compensated pressure readings

to flow into the terminal program.

Type: $*99IN <cr> This is the best way to stop the continuous pressure reading commands.

The $ character temporarily stops, or suspends, either the continuous
pressure or temperature readings. The *99IN command stops the continuous
readings.

 CHANGE TO A NEW SAMPLE RATE

Enter the following command:

Type: *01WE <cr> This enables the HPB to change a parameter in RAM.

Type: *01I=M20<cr> This sets the integration time to value 20, which corresponds to an output

sample every 2 seconds.

The sample rate will change to one every 2 seconds. I= is an abbreviation for Integration time which determines
how long to accumulate pressure samples between readings. Each integration period gathers the data for one
pressure reading output (see Section 4.2 What is integration?). The range of integration times can be set by
specifying readings per second (I=R45 for 45 readings/sec) or time delay in 100 millisecond intervals (I=M60
for 6 seconds). The factory set integration time is 5 samples per second (I=M2). See Section 5.10, command
descriptions, for more detail.

The output data rate can also be altered by use of the idle count (IC) command or by changing the reading rate (RR)
command in conjunction with the operating mode (OP) command. See Section 4 for description of these commands.

 REPEAT THE READ CONTINUOUS PRESSURE STEP ABOVE

Notice the slower output rate of one sample every 2 seconds.

4

 TRY OTHER COMMANDS

Experiment with other commands to become familiar with the command structures. A short overview of each command
with input and response examples is shown in Section 3 Commands  Quick Reference. See Section 5Commands
for complete command descriptions. Until an SP=ALL command is executed, no changes will be stored in the
EEPROM. Cycle the power or send an IN=RESET command to revert to previous EEPROM settings.

2.7 Command Functional Groups

 PRESSURE DISPLAY UNITS HPB reads out psi, in wc, mm Hg, etc.

DU Set pressure units for output readingsany one of 17 units
U= Specify a user supplied unit of measure

 TEMPERATURE

T1 Single °C
T2 Continuous °C
T3 Single °F
T4 Continuous °F

 RING/MULTI-DROP BUS PARAMETERS

BP Changes baud rate and parity
ID Assign device ID and group addresses
M= Select alternate message Headers [Multi-Drop]
SI Synchronize Integration cycles among units [Multi-Drop]
TO Set Transceiver Operating parameters

 OUTPUT READING AND RATESpeed up or slow down output rate

Single Reading Commands

P1 Single pressure reading...ASCII format
P3 Single pressure reading...binary format
T1 Single temperature reading...°C
T3 Single temperature reading...°F

Continuous Readings Commands

P2 Continuous pressure readings...ASCII format
P4 Continuous pressure readings...binary format
T2 Continuous temperature readings...°C
T4 Continuous temperature readings...°F

Integration Time Commands Changes pressure reading response time

DS Set deadband and sensitivity parameters
I= Set pressure integration time and reading rate
SI Synchronize pressure Integration cycles

Idle Count Command Changes pressure reading response time

IC Set number of idle integration cycles

Reading Response To Changes In Input PressureFilters small changes

RR Set number of identical readings to skip
OP Transmit all readings or only changed readings

5

 FORMAT PRESSURE READINGSChanges data length into host processor

Binary Format Commands

P3 Single pressure...binary format
P4 Continuous pressure...binary format
OP Set operating mode...binary format checksum...set signed or extended binary output format

ASCII Format Commands

All readings, except P3, P4 and ~, are ASCII format readings.

OP Set operating mode...all readings or only changed readings

 START-UP PARAMETERSSets the HPB configuration after power is applied

WE Enable parameter writes to the RAM or EEPROM
SP Store RAM parameters to the EEPROM for startup
MO Specify the power-up message and operating mode

 PRESSURE NOISE REDUCTIONReduces pressure noise signals

DS Set deadband and sensitivity parameters

 DIAGNOSTIC AND RESET CONTROL

IN Performs a software reset of microprocessor
RS Read status of error indicators
CK Performs and provides the result of EEPROM checksum
OP Use pressure reading checksum for binary format

 USER AND STARTUP MESSAGES

A= Store 8 characters of user supplied data
B= Store 8 characters of user supplied data
C= Store 8 characters of user supplied data, which can be configured as a watchdog or reset message
D= Store 8 characters of user supplied data, which can be configured as a watchdog or reset message
MO Specify the startup header selection

 HPB UNIT INFORMATION

P= HPB production date
S= HPB serial number
V= HPB software version number
ID Assign device ID and group addresses
M= Read the maximum full scale pressure limit allowed

 CUSTOMIZE PRESSURE WINDOW

F= Customize the full scale pressure limit
X= Set the slope m parameter for user input mx+b control
Z= Set the offset b parameter for user input mx+b control

6

3.0 COMMANDSQUICK REFERENCE

A= Data String A

(up to 8 characters, a <cr> indicates end-of-message. *00A=2-8-95
More than 8 characters is an invalid write)
(Can store info. such as dates, readings, etc.) Inquiry *00A= ?01A=2-8-95

BP Baud Rate and Parity Setting

B= Data String B

(up to 8 characters, a <cr> indicates end-of-message, *00B=123.4567
and more than 8 characters will not write to location)
(Can store info. such as dates, readings, etc.) Inquiry *00B= ?01B=123.4567

CK Check EEPROM

C= Data String C

(up to 8 characters, a <cr> indicates end-of-message, *00C=This_is_
and more than 8 characters will not write to location
The C and D string can be used for a watchdog or reset
message(see MO command). Inquiry *00C= ?01C=This_is_

DO Default Operating Parameters

(factory default setting) *00DO=E

DS Deadband and Sensitivity Control

set deadband to 20 x 0.005% = 0.10%FS ) *00DS=20

DU Display Units Control

D= Data String D

(up to 8 characters, a <cr> indicates end-of-message, *00D=A_HPB!!!
of more than 8 characters will not write to location)
The C and D string can be used for a watchdog or reset
message (see MO command). Inquiry *00D= ?01D=A_HPB!!!

F= Custom Full Scale Range

(set custom FS range to 10.5psi) *00F=10.5

Example Example
Input (1) Response (2)

Write string A *00WE

Set parameters *99WE

(no parity, 1200 baud) *99BP=N1200

Write string B *00WE

Inquiry *00CK ?01CK=OK

Write string C *00WE

Set DO parameters *00WE

Inquiry *00DO ?01DO=E0NX

Set DS parameters *00WE

Inquiry *00DS ?01DS=00S0

Set DU parameters *00WE

(set units to in. Hg) *00DU=INHG

Inquiry *00DU ?01DU=INHG

Write string D *00WE

Set F= parameter *00WE

Inquiry *00F= ?01F=10.500

Note: See Section 5.10 for complete command descriptions.

7

IC Idle Count Parameter

Set IC parameter *00WE

(set idle count to 12 , so that 12 output samples are skipped) *00IC=12

Inquiry *00IC ?01IC=12

ID Identification Number

Set ID number *00WE

(set device ID of first null addressed unit to 12) *00ID=12

Confirmation of ID=12 *12P1 #12CP= 14.32

Set group number *12WE

[Ring Network] (set group ID of unit 12 to 95) *12ID=95

[Ring Network] Group no. inquiry of device ID=12 *12ID #12ID=95

[Multi-Drop](set group ID of unit 12 to 95 with group sub-address of 01) *12ID=9501

[Multi-Drop] Group no. inquiry of device ID=12 *12ID #12ID=9501

IN Initialize HPB Microprocessor

Stop all current operations *99IN

(does not affect RAM data)

Full reset of HPB processor *99IN=reset

Changes to RAM data are lost unless an SP =ALL command

was previously issued. (Response is user message, if selected) ?01Pressure_tank_1

I= Integration time

Set I parameter *00WE

(set output rate to 50 readings/second) *00I=R50

Inquiry *00I= ?01I=R050

M= Maximum Full Scale Value Allowed

(Factory set) Inquiry *00M= ?01M=0017psia

MO Power Up Mode

Set MO parameter *00WE

Required to save in EEPROM for power-up *00SP=ALL

Inquiry *00MO ?01MO=X2M1

OP Operating Mode Parameters

Set OP parameter *00WE

(set to extended binary output mode) *00OP=E

Inquiry *00OP ?01OP=ANEW

P1 Pressure, Single, ASCII Format

Request compensated pressure *00P1 ?01CP= 14.450

P2 Pressure, Continuous, ASCII Format

Request compensated pressure *00P2 ?01CP= 14.450

P3 Pressure, Single, Binary Format

Compensated pressure (null address) *00P3 ^@PSA or

Compensated pressure (assigned address) *01P3 {@PSA

(typical response is a ^ or { char plus 4 data bytes

that are encoded for computer translation)

Example Example
Input (1) Response (2)

*00MO=M1
*00WE

(repeated)

Note: See Section 5.10 for complete command descriptions.

8

P4 Pressure, Continuous, Binary Format

Compensated pressure (null address) *00P4 ^@P@@ or

Compensated pressure (assigned address) *01P4 {@P@@

(typical response is a ^ or { char plus 4 data bytes (repeated)

that are encoded for computer translation)

P= Production Date

(factory set date, mm/dd/yy) Inquiry *00P= ?01P=09/26/00

RR Reading Rate

(skip 5 x 100 = 500 readings if identical) *00RR=5

RS Read Status

SI Synchronize Pressure Integration

SP Store Parameters in EEPROM

(store all settings stored in RAM in EEPPROM) *00SP=ALL

S= Serial Number

T1 Temperature, Single, °C

T2 Temperature, Continuous, °C

T3 Temperature, Single, °F

T4 Temperature, Continuous, °F

T0 Transceiver Operating Parameters

Set multi-drop response delay to 2 character times *01WE

U= User Supplied Display Units

V= Version Number

Example Example
Input (1) Response (2)

Set RR parameter *00WE

Inquiry *00RR ?01RR=5

Inquiry *00RS ?01RS=0000

Synchronize Integration *01SI

Store Parameter *00WE

Inquiry *00S= ?01S=00005137

Request Celsius temperature *00T1 ?01CT=24.5 or ?01CT=..

Request Celsius temperature *00T2 ?01CT=24.5 (repeated)

Request Fahrenheit temperature *00T3 ?01FT= 76.1 or ?01FT=..

Request Fahrenheit temperature *00T4 ?01FT=76.1 (repeated)

*01T0=2

Inquiry *01T0 #01TO=M2C

Set display units *00WE

(set units to 5.1 x psi) *00U=5.100

Activate user display units *00WE *00DU=USER

Inquiry *00U= ?01U=5.100

Inquiry *00V ?01V=H2.4E0Mnn

Note: See Section 5.10 for complete command descriptions.

9

Example Example
Input (1) Response (2)

WE Write Enable to EEPROM or RAM

Write several RAM parameters *01WE=RAM

(example to set output units to cm water column) *01DU=CMWC

(factory default setting) *01DO=E

(Cancel continuous WE=RAM command) *01WE=OFF

Note:Any command changes in RAM will be lost when the PPT is powered down unless an SP command

saves them to EEPROM.

X= Slope - User Compensation Control

Set X= parameter *00WE

(set user slope control to 0.005% x 17 = 0.085%FS) *00X=17

Inquiry *00X= ?01X=17

Note:The input slope and offset control are for user supplied mx+b correction.

Z= Offset - User Compensation Control

Set Z= parameter *00WE

(set mx+b pressure offset to 20 x 0.005%FS = 0.1%FS) *00Z=20

(null adjust output at zero pressure) *00Z=CAL

Inquiry *00Z= ?01Z=20

(1) A carriage return, <cr>, should follow each input. If the HPB has an established address of 12, for instance, then

begin the command with *12.. instead of *00...

(2) The responses shown here begin with ?01.. and are for a null address HPB. That is, a HPB that has not yet

established unit identification (see ID command). If the HPB has an assigned address of 23, for instance, the
response will begin with #23.. instead of ?01...

Note: See Section 5.10 for complete command descriptions.

10

4.0 FUNCTIONAL OPERATION

4.1 Overview

Honeywells Precision Pressure Barometer (HPB) is based on a silicon piezoresistive sensor coupled with a
microprocessor and other electronic circuitry. The Piezoresistive sensor contains both pressure sensitive and
temperature sensitive elements. After testing the sensor over a matrix of pressure and temperatures at the factory,
values are stored in the EEPROM and used by the microprocessor to correct for any sensor non-linearities. Because
of the internal digital circuitry, having a digital output capability is straight forward. The digital readings are
transmitted via TTL-level signals in either a ring or multi-drop configuration. When connected to a computer via an
RS232-to-TTL converter, the user can modify the pressure reading rate, integration times, units of pressure,
thresholds for deadbands, etc.

Pressure

Input

HPB

Pressure

Sensor

Temperature

Sensor

16 bit

Analog

to

Digital

Converter

EEPROM

Micro-

processor

RAM

Voltage Regulator

TTL-Level

COM

(Digital

Serial
Data)

Figure 1. HPB Block Diagram

The HPB can be tailored to specific application requirements. Configuration information is sent to, or read from,
the HPB by user command messages over the serial port. Most configuration parameters that can be changed by a
command may be retrieved by use of that same command. Commands used to change parameters must be preceded
by an enabling command (WE), but commands used to retrieve information do not require an enable. All
configuration changes are stored in the HPB RAM for immediate use until power is removed. These configuration
changes are only made permanent in the EEPROM when the user executes the Write Enable (WE) command
followed by the EEPROM Store Parameters (SP) command. (Exceptions to this are the A=, B=, C=, and D=
commands, which are immediately stored to EEPROM if preceded by the WE command.)

DC
Power

Power
Control

The HPB is a low power device. It can be configured to enter a micro-power shut down mode by either sending a
simple command (See OP=O Command) or by applying +5V to the power control pin on the electrical connector.

If the micro-power mode was entered with a simple command, normal operation is restored by momentarily
grounding the power control pin. If the HPB was configured to enter a micro-power state by applying +5V to the
power control pin (See OP=P Command), normal operation is restored by permanently grounding the power control
pin.

11

4.2 What Is Integration?

The input pressure is converted to an analog electrical signal at the pressure sensor. This signal feeds into a delta­sigma analog-to-digital (A/D) converter where it is changed into a digital signal representing the pressure value.
During the A/D conversion cycle, the signal is integrated over time. That is, the pressure reading is averaged
(integrated) over the A/D conversion cycle so the resultant digital value is the summation of the average pressures
observed during the cycle. This conversion cycle can be controlled by the user with the Deadband and Sensitivity
(DS), Synchronization Integration (SI), Idle Count (IC), and Integration (I=) commands.

4.3 Pressure Reading Control

The HPB commands allow considerable flexibility in tailoring pressure acquisition times, sample windows, thresholds,
and output rates. These are controlled by five commands: Deadband and Sensitivity (DS), Integration (I=), Idle Count
(IC), Reading Rate (RR), and OPerating mode (OP). Figure 2 illustrates how the user may control these attributes in
three ways:

First, the internal analog-to-digital converter integration time may be controlled over a range of 1 sample every 12
seconds up to 120 samples per second. This is controlled using the Integration (I=) command. The integration time
is used to control the A/D integration cycle that allow noisy pressure inputs to be filtered, or averaged, over a
selected period of time. See Figures 5. The integration time can be set within a range of 1 to 120 samples/sec using the
I=Rn form or a range of 100msec to 12 sec/sample using the I=Mn form. The values for n range from 1 to 120 for
both the rate (Rn) form and the millisecond (Mn) form.

Second, the integration cycles may be spaced with idle periods that cause pressure reading times to increase to only
as one every 51 minutes. The Idle Count (IC) command will skip from 0 to 255 idle periods equal to the
integration time. If the integration time is set to the maximum, 12 sec/sample, and an idle count of 255 is selected, then
the time between samples = 12 sec. x 256 = 51.2 minutes.

Third, the reading rate may be controlled so pressure readings are obtained only when pressure changes occur. The
Reading Rate (RR) command can be set to output only changed readings, or skip from 100 to 1000 identical readings.
The Operating Mode command (OP) can be set to output every reading or to only output changes. The Deadband
setting in the DS command can filter a small pressure change by not allowing the pressure reading to vary as long as
it remains within the deadband limits. This controls the sensitivity to change of the RR and OP command modes
when the output only when pressure changes options are selected. If the pressure signal is stable within the
deadband limit, then the pressure reading time can be increased up to 1000 times the integration time by using the RR
command.

12

IC = c

Idle Count

(IC=0 factory default)

if c = 0 then no output

Delay

if c = 1 - 255 then add 'c' wait

cycles between inputs

if I = Mn

if I = Rn

Scalar

Display Units

Pressure

P1, P2, P3, P4

TD, RD

Output Mode

and Format

• Single or Continuous

Digital

Outputs

TTL-Level

• ASCII or Binary

Pressure Values

Display Units

HPB Pressure Rate Conditioning

User Compensation

Dead Band

DS = dd Sn

(DS=00S0 factory default)

DB = n x dd x 0.005% FS range

(dd= 0 - 60, n=1, 2, 4, or 8)

(X=m, Z= b)

Press. = mX + b

User Compensation

X=nn, Z=nn

(X=1.000 factory default)

Dead Band and Sensitivity

A/D

Converter

Integration

I = Rn or I = Mn

(I=M002 factory default)

Integration Time

range for n value: 1-120

Rn: n readings/sec

Mn: n x 100 msec/reading

Input

Pressure

RR = r

Reading Rate

(RR=00 factory default)

OP = d m n p

Operating Mode

Output Control

(OP=ANEX factory default)

Output Control

if r = 0 then output every input

if r = 1 - 10 then skip r x 100

identical readings

if d = A then output every input

if d = U then output only changes

if p = X then no watchdog timer

if p = W then use watchdog timer

For binary format mode:

if m = N then no checksum

if m = C then use checksum

if n = S then use standard format

if n = E then use extended format

Shaded blocks represent command codes executed in the microprocessor

Figure 2. Pressure Reading Control

13

4.4 Customized Pressure Range

The user can adjust the pressure vs. output value transfer curve using the X=, Z= and F= commands. The X=
command adjusts the slope of the pressure output curve. The range of adjustment for X=, and Z= commands is
±0.6%FS in 0.005% increments. The F= command can change the full scale pressure span to any value between 50%
and 100% of the factory specified range (M=).

The purpose of these commands is to allow the user to provide compensation for the pressure values specific to an
application. This type of adjustment is made after the HPB temperature compensates the pressure reading according
to the factory calibration. The user supplied values (X=, Z=) are used as an mx+b correction. The X= command
supplies the slope adjustment, or m, value and the Z= command supplies the offset adjustment, or b, value.
Figures 3 and 4 illustrate these commands.

1200 hPa

Digital Output

+0.6%FS

Figure 3. Custom Slope (X=) Options

○○○

- 0.6%FS

1200

Slope=1

Digital Output

Applied
Pressure (hPa)

Figure 4. Custom Offset (Z=) Options

+0.6% FS

○○○

Offset=0

- 0.6%FS

1200

Applied
Pressure (hPa)

The user compensated pressure output can be expressed in terms of X= slope values m where m=0 to ±120. The
offset value, Z=, can be expressed as b where b=0 to +120.

Pressure Output = [(1 + m x 0.00005) x Pressure Reading] + [(b x 0.00005) x (full scale)]

The F= command is used in conjunction with the X=, and Z= command to customize the full scale range and user
compensation of the HPB. The F= command allows the user to reduce the full scale range of the HPB as much as
one-half the factory FS value. The F= command value can have up to 5 significant digits with a decimal point. Enter
an F=0 command to disable this function and return to the factory default (M=) full scale value. Using the
F= command, the maximum allowable full scale pressure is the M= value and the minimum allowable FS pressure is
(0.5 x the M= value). The new F= value becomes the standard FS number used for other commands and range
calculations. (Note that the accuracy specification is always referenced to the factory (M=) full scale value.) For
example, to customize the full scale range of a 1200 hPa (900mm Mercury - mmhg) device to 800 mmhg, first select
the desired display units using the DU command. Enter the command *ddWE followed by a *ddDU=mmhg. Then
enter a *ddWE followed by a *ddF=800. The full scale pressure for this unit is now 800 mmhg.

14

4.5 Command Illustrations

The figures below illustrate the commands that affect the pressure output rate. Figure 5 shows a varying pressure
signal having a reading integration time of 200 msec. If the small variations on the pressure signal are considered
noise and are undesirable, increase the integration time to time-average the pressure signal, and filter out the noise.

Pressure

5.24

5.20

5.16

5.12

5.08

5.04

5.00

4.96

4.92

(psi)

1.0 2.0 3.0

Integration Time

Integration Time = 0.2 sec

(I=M2 sets 2x100 msec/sample)

(0.2 sec)

I = M2 IC = 0
RR = 0 OP=A

Integration time
HPB pressure output
Actual pressure

Time (sec)

Figure 5. Integration (I=) Command, Example 1

Figure 6 shows the same pressure signal with a 1 second integration time reducing the noise variations on the output
readings. Of course, the penalty for doing this is reducing the response time to rapidly changing pressures that are
not considered noise.

Integration Time (1 sec)

Integration Time = 1 sec

(I=R1 sets 1 reading/sec)

I=R1 IC = 0
RR = 0 OP=A

Integration time
HPB pressure output
Actual pressure

5.24

5.20

5.16

5.12

5.08

5.04

5.00

4.96

4.92

Pressure

(psi)

1.0 2.0 3.0

Time (sec)

Figure 6. Integration (I=) Command, Example 2

15

Figure 7 shows the effect of the deadband setting in the DS command. If a deadband of ±0.02% FS is selected, then
the pressure output will not change reading as long as it is within this limit (±2.4hPa for a 1200 hpa unit). If the
pressure exceeds or falls below this threshold, the pressure reading will track the actual pressure value. It will
continue to track the pressure value until there is no change again within the threshold limit.

Figure 8 illustrates the effect of the Idle Count (IC) command for four different pressure curves. The IC command
does nothing more than skip over a set number of readings. If the idle count were set to IC=4, then after a pressure
output reading, the HPB would not output the next 4 readings and the fifth one would become the next output
reading. This feature allows the reading rate to be established different from the integration time. This feature is
useful for minimizing the communications traffic on a network of many HPB units.

Figure 9 illustrates the Synchronize Integration cycle (SI) command as well as the Transceiver Operating parameters
(TO) options that affect it. This is only for units configured to multi-drop operation.

16