iWorX TM-100 Technical Note

TM-100 Temperature Sensor

Technical

Note

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TM-100

Overview

The TM-100 Temperature Sensor is a sensor that can monitor temperatures
between 15°C above and 15°C below room temperature. The TM-100 is capable of
responding to changes in temperature within a few seconds because of its small
size (1mm x 3mm) and mass. The TM-100 is suitable for monitoring the
temperature of nasal airflow, changes in skin temperature that indicate evaporative
cooling, and changes in atmospheric temperature and temperature in
environmental chambers. Since the sensor element is water-resistant, the tip of the
TM-100 can be immersed in aqueous solutions, including saline solutions, for a
few hours.

How It Works

The sensor element in the TM-100 that responds to temperature changes is a
thermistor, which is a type of resistor that changes resistance with changes in
temperature. The thermistor in the TM-100 has a negative temperature coefficient
(NTC) which means that the resistance of the thermistor decreases as the
temperature goes up. Thermistors with positive temperature coefficients also exist.
Table 1 at the end of this Technical Note shows the resistances of the thermistor in
the TM-100 over a range of temperatures from 0°C to 50°C.

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The thermistor in the TM-100 is wired into the circuit of the sensor as one leg of a
Wheatstone bridge. On the other three legs of the bridge circuit, selected resistors
are used to give the TM-100 a linear output over a range that is 15°C above and
below room temperature.

TM-100 Temperature Sensor

How to Use the TM-100

Equipment Setup

1) Insert the DIN8 connector of the TM-100 temperature sensor into a DIN8
extension cable.

2) Insert the other end of the DIN8 extension cable into a DIN8 transducer input
on an iWorx data acquisition unit or amplifier.

Start the Software

1) Open LabScribe by clicking on the LabScribe desktop icon.

2) When the program opens, select Preferences from the Edit menu (or from

the LabScribe menu on a Macintosh computer).

3) Select the Channel preferences dialog window. Name the channel to which

the TM-100 is connected. Set the Mode/Function for this channel to DIN8.
Also, set the sampling rate and display time. Click OK.

Calibration of the TM-100 Temperature Sensor

1) Prepare two beakers of water, one at 10

the temperature of the cold water with a thermometer just before the TM-100
temperature sensor is placed in the beaker.

2) Place the tip of the TM-100 temperature sensor in the center of the beaker of
cold water.

3) Click the Start button on the Main window of the LabScribe software and

begin recording. Type “Calibration at <Cold Water Temperature>” on the
comment line to the right of the Mark button.

4) After about twenty seconds in the cold water, the output of the TM-100

temperature sensor displayed on the recording channel should reach a stable
level. Press the Enter key on the keyboard to mark the recording. Continue
recording.

5) Measure the temperature of the warm water with a thermometer just before the

TM-100 temperature sensor is placed in the beaker. Type “Calibration at
<Warm Water Temperature>” on the comment line.

6) Continue recording as the temperature sensor is moved from the cold water to
the warm water.

7) After about twenty seconds in the warm water, the output of the TM-100

temperature sensor displayed on the recording channel should reach a stable
level. Press the Enter key on the keyboard to mark the recording. Click Stop
to halt the recording.

8) Select Save As in the File menu, and type a name for the file. Choose a

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destination on the computer in which to save the file. Click on Save to save
the file.

o

C, and the other at 40oC. Measure