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Post by wootie on May 13, 2024 16:50:22 GMT -5
Hello,
Typically we only use LN2 with our cryostat and the temperature controller, Lakeshore 331, works well. We've recently installed a closed helium system and on the first cool-down, the temp. controller sensor A said "S. Over", while sensor B said "T. Over". My understanding is that "S. Over" is a short; while, "T. Over" involves the calibration curve? How do we fix these problems? Thanks!!
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Post by Lake Shore Jeff M on May 14, 2024 7:24:28 GMT -5
Actually, S. Over normally indicates an open. S. Over says the input is above the maximum value it can read. For a silicon diode sensor, that is 2.5V, for a NTCRTD sensor, it is 7500 ohms and for a platinum sensor, it depends on which range you select, normally 250 or 500 ohms.
T. over indicates that the sensor value is outside of the highest temperature on the curve. For a diode and NTCRTD sensor that would be a low value and for a platinum sensor it would be a high value for that sensor.
In order to help troubleshoot the issue further, I need to know what type of sensors you have assigned to the inputs and which one is showing the S. Over and/or T. Over.
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Post by wootie on May 14, 2024 8:29:37 GMT -5
I have three cryostats and of course, the one I'm using I cannot find the manual with specifications. Would you be able to look it up? It's a Janis ST-300 with serial number 12619/19847/20187 assigned to J. Heremans at OSU. If not, I can reach out to Lakeshore via email.
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Post by Lake Shore Jeff M on May 14, 2024 9:05:17 GMT -5
12619 is a ST-300T and it has 2, TG-120-SD-1.4H GaALA diodes, max voltage is 7.5V
19847 and 20187 were repairs that did not affect the sensors.
If you are seeing S. Over, that means the voltage exceeds 7.5V. T, Over would indicate a voltage less than 0.3V
If you send an email to support@lakeshore.com, I can send you our diode sensor troubleshooting guide so you can measure different resistances to determine why you are seeing the fault.
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