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Post by alcrityf174 on Sept 27, 2017 10:53:30 GMT -5
 Hi, I was hoping to get some advice ref these temp sensors. Here in our lab we are trying to reinstall an antiquated cryogenic tool. Basically a heat exchanger connected to a cryo cold head. The heat exchanger has two temp sensors. I carried out some basic tests, they have two wires connected to an electrical connector outside of the vacuum vessel. They seem to be some version of a diode. I made up a set of jumper leads to turn the two wires into 4 wires. Then using a lakeshore current source and a multimeter attempted to measure the voltage drop and using the standard charts obtain a temp. Current source is set to 10ma. Unfortunately the voltage drop measured does not relate to anything on these charts, I am getting 0.867v nowhere near what I was expecting for rt. Not my field of expertise so any advice greatly appreciated. |
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Post by Lake Shore Jeff M on Sept 27, 2017 11:37:47 GMT -5
When using a current source and voltmeter to test a diode sensor, set the current to 10uA and depending on which model of diode sensor you have, the resulting room temperature voltage should be between 0.36V up to 0.56V, however, if the cryostat you have is equipped with a magnet, the sensor may be a GaAlA, gallium aluminum arsenide diode, which does produce a voltage of approximately 0.89V at room temperature.
If you would like additional assistance in this, please email service@lakeshore.com. |
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Post by alcrityf174 on Sept 27, 2017 11:48:23 GMT -5
Many thanks,
No magnets involved.
I misunderstood the current value. Was using 10ma rather than 10uA
Now I have a reading of 0.57v So 21.85 deg C.
That makes more sense.
Thanks for the advice it's much appreciated.
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Post by Lake Shore Jeff M on Sept 27, 2017 12:18:06 GMT -5
0.57V Sounds like you may have a DT-670 sensor. On the DT-670 curve, 0.57V would indicate 295.5K
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Post by alcrityf174 on Sept 27, 2017 14:40:42 GMT -5
0.57V Sounds like you may have a DT-670 sensor. On the DT-670 curve, 0.57V would indicate 295.5K I think you are correct, Started up the system, from RT to 35K and still dropping. Very happy. Thanks |
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