28022 Datasheet 28022 | P1-P3

Parallax, Inc. • DS2760 Thermocouple Kit (#28022) • 01/2004

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Rocklin, California 95765, USA

Office: (916) 624-8333

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General: info@parallax.com

Technical: support@parallax.com

Web Site: www.parallax.com

Educational: www.stampsinclass.com

DS2760 Thermocouple Kit (#28022)

1-Wire

Thermocouple Interface

Introduction

Thermocouples provide a low-cost, reliable means of measuring temperature over a wide range. The

challenge when using a thermocouple is accurately measuring the very low Seebeck output voltage

(fractional to low millivolts) from the element, and providing for cold junction temperature compensation.

The Dallas/Maxim DS2760 High Precision Li+ Battery Monitor is very easily configured into an effective

thermocouple interface. The Parallax DS2760 Thermocouple Module capitalizes on this application and

provides a complete connection between the BASIC Stamp and a standard thermocouple element.

Features

 1-Wire

interface allows multiple devices with just one Stamp IO pin

 Cold Junction measurement: 0°C to +127°C (0.125°C resolution)

 Low power consumption:

-- Active current: 90 A max

-- Sleep current: 2 A max

Packing List

Verify that your DS2760 kit is complete in accordance with the list below:

 DS2760 Thermocouple Module #550-28022

 (3) Thermocouple elements:

-- (1) K-type (Chromel / Alumel) #800-00011

-- (1) J-type (Iron / Constantan) #800-00012

-- (1) T-type (Copper / Constantan) #800-00010

 This documentation

Note: DS2760 demonstration software may be downloaded from www.parallax.com.

Parallax, Inc. • DS2760 Thermocouple Kit (#28022) • 01/2004

Connections

Before connecting the DS2760 Thermocouple Module to the BASIC Stamp you will need to prepare a

thermocouple element, and then connect it to the cold junction port of the module. Start by carefully

removing about one inch (250 mm) of the outer sleeve from each end of the element. From each lead on

the temperature measurement end, remove about ½ inch (125 mm) of insulation and then carefully twist

together (using pliers if necessary) and trim as shown in Figure 1.

Figure 1: Thermocouple Junction

On the cold junction (DS2760 module) end of the element, remove only ¼ inch (60 mm) of insulation from

each lead. Route these leads through the bottom of the thermocouple module PCB and insert snuggly

into the pin sockets as shown in Figure 2.

Figure 2: Cold Junction Connection to DS2760 PCB

Use this table to ensure that you make the proper thermocouple connections to the module. If the leads

are reversed, the measured temperature will be incorrect.

Type Materials SNS Vss

K Chromel / Alumel Red Yellow

J Iron / Constantan Red White

T Copper / Constantan Red Blue

Finally, the DS2760 Thermocouple Module is connected to the BASIC Stamp as shown in Figure 3 below

(Note that the module includes a 4.7 K pull-up on the 1-Wire

data line).

Figure 3: DS2760 Connections to BASIC Stamp

Vdd

Vss

Data IO

Parallax, Inc. • DS2760 Thermocouple Kit (#28022) • 01/2004

BASIC Stamp Application

The following BASIC Stamp application will run on either the BS2p or BS2pe and demonstrates how easy

measuring wide-range temperatures can be when using the DS2760 Thermocouple Module. Other

Stamps will require a Serial-to-1-Wire protocol converter, as well as code to manage the large tables

across program slots, and are not covered in this document.

A little background: When two dissimilar metal wires are joined, a voltage will be developed across the

open end that is proportional to the temperature difference between the joined and open ends. This

effect was discovered by Thomas Seebeck in 1821. Through empirical testing, voltage tables have been

established that correspond to the thermocouple junction temperature. These tables, however, use a

cold junction (voltage measurement point) reference of zero degrees Celsius, forcing electronic devices to

employ cold junction compensation.

Using the DS2760 we can measure the Seebeck voltage from the thermocouple with a resolution of

15.625 microvolts, then measure the cold junction temperature with a resolution of 0.125 degrees

Celsius. A simple table look-up using the cold junction temperature will give us the cold junction

compensation voltage. This is combined with the Seebeck voltage and, using a modified binary search

algorithm, we can determine the compensated temperature from the thermocouple data table.

' =========================================================================

' File...... DS2760TC_Demo.BPE

' Purpose... Thermocouple temperature measurement using the DS2760

' E-mail.... support@parallax.com

' Started...

' Updated... 19 JAN 2004

' {$STAMP BS2pe, KTablePos.BPE, JTablePos.BPE, TTablePos.BPE}

' {$PBASIC 2.5}

' =========================================================================

' -----[ Program Description ]---------------------------------------------

' This program lets a BS2p or BS2pe read the temperature from the Parallax

' DS2760 thermocouple module. User input of thermocouple type (K, J, or T)

' and temperature display is via the DEBUG window.

' -----[ Revision History ]------------------------------------------------

' -----[ I/O Definitions ]-------------------------------------------------

OW PIN 8 ' 1-Wire buss pin

P1-P3 P4-P6 P7-P8

28022

Mfr. #:

Buy 28022

Manufacturer:

Parallax

Description:

Sensor Development Tools Temperature Sensor Development Tools DS2760 THERMOCOUPLE KIT

Lifecycle:

New from this manufacturer.

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