B&B Electronics 232DTT User Manual

Digital Thermometer & Thermostat

with RS-232 Interface

Model 232DTT

Document No. 232DTT1795

B&B Electronics Mfg. Co. Inc.

P.O. Box 1040 -- Ottawa, IL 61350

PH [phone] -- FAX [phone]

Internet:

http://www.bb-elec.com

[e-mail]

[e-mail]

B&B Electronics -- April 1995

232DTT1795 Manual Cover Page

B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350

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TABLE OF CONTENTS

CHAPTER 1. GENERAL INFORMATION.................................. 1

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

FEATURES ..................................................................................... 1

PACKING LIST ................................................................................ 1

SPECIFICATIONS ............................................................................ 1

RS-232 CONNECTIONS.................................................................. 2

CHAPTER 2. 232DTT FUNCTIONS.......................................... 3

DIGITAL THERMOMETER ................................................................. 3

PROGRAMMABLE THERMOSTAT ...................................................... 3

CHAPTER 3. 232DTT DATA FORMAT..................................... 5

CHAPTER 4. 232DTT COMMANDS.......................................... 7

READ TEMPERATURE ..................................................................... 7

READ STATUS................................................................................ 7

READ HIGH.................................................................................... 8

READ LOW .................................................................................... 8

CLEAR STATUS REGISTER.............................................................. 8

SET HIGH THERMOSTAT ................................................................. 9

SET LOW THERMOSTAT.................................................................. 9

CHAPTER 5. SOFTWARE....................................................... 11

INSTALLATION .............................................................................. 11

WINDOWS SETUP ........................................................................ 11

APPENDIX A. USING SIMPTERM..........................................A-1

APPENDIX B. DECIMAL/ASCII TABLE.................................B-1

232DTT1795 Manual Table of Contents

B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350

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Chapter 1. General Information

Introduction

The 232DTT is a digital thermometer and thermostat which
operates through an RS-232 interface. Non-volatile registers hold
programmable high and low thermostat settings. Current
temperature is reported by polling the DTT, while thermostat
operations continue as long as the unit is powered.

Features

• ±0.5 °C accuracy and resolution

• High, low and hysteresis type thermostat outputs

• Port-powered from host RS-232 port (RTS & DTR high)

• Thermostat thresholds programmable in non-volatile registers

• Status Register latches if thermostat outputs have tripped

Packing List

Examine the shipping carton and contents for physical
damage. The following items should be in the shipping carton:

1. 232DTT unit

2. One 232DTT 3.5” disk

3. This instruction manual
If any of these items are damaged or missing, contact B&B
Electronics immediately.

Specifications

Communications:

Standard: RS-232 (unit is DCE)
Baud Rate: 1200 to 9600 (automatic detection)
Format: 8 data bits, 1 stop bit, no parity
Connector: DB-25S (female)

Thermometer Error

±0.5 °C from 0 - 70° C
(±0.9 °F from 32 - 158°F)
±1 °C from -40 °C to 0 °C and 70 °C to 85 °C *
(±1.8 °F from -40 °F to 32 °F and 158 °F to 185 °F)

* The 232DTT is guaranteed to operate from 0-70 °C.

232DTT1795 Manual Chapter 1 1

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Thermometer Resolution

0.5 °C (0.9 °F)

Temperature Conversion Time

1 second

Open Collector Thermostat Outputs

Low (on) voltages: 1.2VDC @ 100 mA max.
High (off) voltages: 40VDC max.

Power Supply

Port powered with RTS and DTR outputs set high
External power: 12VDC @ 30mA

NOTE: When using an external supply, the supply should be
connected only to specifically labeled power inputs (power
jack, terminal block, etc.). Connecting an external power supply
to the handshake lines may damage the unit. Contact technical
support for more information on connecting an external power
supply to the handshake lines.

RS-232 Connections

The 232DTT communicates using pins 2, 3, and 7 (TD, RD
and GND). However, power is drawn from the handshake lines RTS
(pin 4) and DTR (pin 20). These connections must be present to
power the unit.

Table 1. RS-232 Pinouts

Signal Pin
TD 2
RD 3
RTS 4
GND 7
DTR 20

2 Chapter 1 232DTT1795 Manual

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Chapter 2. 232DTT Functions

Digital Thermometer

The 232DTT continuously measures temperature, with a
new measurement completed once per second. When a Read
Temperature command is received, the DTT immediately reports
back the result of the last measurement completed.

Programmable Thermostat

The 232DTT also functions as a thermostat. Two non­volatile registers can be programmed. The high threshold register,
TH, is programmed using the !0SH command. The low threshold
register, TL, is programmed using the !0SL command. A complete
command description can be found in Chapter 4. Thermostat
operation is a continuous background function. As long as the unit is
powered, the thermostat outputs will be serviced.

Three open collector outputs provide thermostatic controls.
These outputs are current sinking (low) when on, high impedance
(high) when off.

1. T

user programmed TH register.

2. T

the user programmed TL register.

3. T

TH register and turns off when the temperature is equal to or
less than the TL register. This output allows the user to program
any amount of hysteresis.

- Turns on when the temperature equals or exceeds the

HIGH

- Turns on when the temperature is equal to or less than

LOW

- Turns on when the temperature equals or exceeds the

COM

Remember, these are open collector outputs. They do not
source any current (similar to a contact closure to ground). For
example, to drive a relay with a 12VDC coil with the TCOM output,
connect as follows:

1. Connect +12Vdc to one side of the relay coil.

2. Connect the other side of the coil to the TCOM output.

3. Connect the ground of the 12V supply to the GND terminal

block.

232DTT1795 Manual Chapter 2 3

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