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Rev A: 0611
5/98
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TEMPTRONIC
CORPOWTIqN
Preparation for
Use
TP04100A interface
&
Applications
2-17.3
Alternative Thermocouple Attachment
2-1
Z3.1
Thermocouple Construction and Attachment Guidelines
Proper thermocouple to DUT contact is essential to insure accurate temperature sensing.
If the standard interface steps given earlier (see Figure 2-12, "DUT Test Fixture Interface") are not consistent
with your test specimen application, then the following alternative sensor to DUT techniques may be
appropriate.
Follow these steps (in accordance with Section
2-
17.2.1, "Sensor Interface Guidelines") to properly construct
and attach thermocouples to DUT specimens:
For Type T thermocouple construction, use a small gauge (#26,
#28,
#30, or #36 gauge) teflon or
kapton coated copper-constantan thermocouple wire.
Using wire thicker than #36 gauge (0.005 inch
/
0.013 mm) will conduct more heat between the test
specimen DUT and the ambient, resulting in less accurate temperature measurements.
Make the thermocouple junction as small as possible.
Do not ground the sensor: if the DUT case is grounded, then isolate the sensor by using a
material which is electrically nonconductive but is an excellent thermal conductor.
It is preferable that the thermocouple junction and approximately 20-30x the thermocouple wire
diameter be in contact with the center of the DUT to minimize heatsinking (see Figure 2-13,
"Alternative Thermocouple Attachment").
Mount the sensor beneath the DUT to shield it from high velocity ThermoStream air.
If the sensor is mounted on top of the device and is in the airstream, then timeltemperature
measurements will not be the actual DUT temperature but be some weighted average of both device
and air temperatures.
The above techniques are illustrated in Figure 2-13, on page 2-36.
Page
2-35
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