at15
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Posts: 5
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Post by at15 on Jul 4, 2024 23:59:21 GMT -5
Hello Sir, I am using Lakeshore model 335 with two lakeshore silicon diodes of DT-670 model for quite a long time. Suddenly one of the temperature sensor is not sensing the temperature properly. Even if I command the programme to use another temperature sensor only, that sensor also is not changing the temperature according to set point at fixed ramp rate. I am not able to find out whether the problem is with temperature sensors or temperature controller. The resistance between I+ and V- of both the diodes is around 26 to 27 megaohms and if I change the polarity of the multimeter, it is showing 0 resistance between the same I+ and V-. Kindly sugggest what should I do? ![]()
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Post by Lake Shore Jeff M on Jul 8, 2024 7:30:16 GMT -5
The first thing I would do is to switch the two diodes between the channels on the 335. If the diode that is working correctly still works correctly on the other channel and the one on the other channel is now not working correctly, it shows that the issue is in the diode or its wiring. If the good channel does not work correctly when moved, it points to a defective input channel on the 335 which will require it be returned for a repair.
Just to clarify, when you measured the diode and see the 26-27 Meg Ohm reading and then reversed the polarity of the probes, did you measure an open circuit or a short?
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at15
New Member
Posts: 5
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Post by at15 on Jul 11, 2024 0:59:03 GMT -5
I switched the two diodes between the channels. Now, the good diode is working correctly and following the set point at a fixed ramp rate; the second diode, which was not sensing the temperature correctly, also following the ramp rate but showing around 15 K temperature more than the set point. I guess the issue is in the wiring of the second diode.
When I measure the resistance between the diodes using a multimeter, it shows around 26-27 mega Ohm resistance between I+ and V-, and when reversing the polarity of the probes, it shows an open circuit.
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Post by Lake Shore Jeff M on Jul 11, 2024 7:18:19 GMT -5
Which diode is the control sensor for the heater output?
If the second diode is the control sensor, it would indicate that you may have a manual output percentage selected that will add to the PID control value which will cause the temperature to settle above the setpoint.
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at15
New Member
Posts: 5
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Post by at15 on Jul 11, 2024 12:13:53 GMT -5
I would like to clarify the problem. I have two DT-670 diode sensors; one is on the sample mount (sensor A, which is the control sensor for heater output), and another is on the sample holder (sensor B). Sensor A and B were connected to temperature controller input A and B, respectively, and were working fine (the only thing is sensor B always used to show 2-3 K lower temperature than sensor A or setpoint. Since both the sensors were following the ramp rate so this small difference was not a problem to us.) Suddenly, Both the sensors stopped to follow the ramp rate according to the given command. When I cooled the sensors using some external source, sensor B did not sense the temperature properly; it sensed the temperature decrease around 290K and then again started to raise the temperature. While sensor A showed the temperature decrease properly as we cooled the sensor using an external source. Although both the sensors showed 26-27 mega Ohm resistance and open circuit when polarity was reversed.
When I switched the diode sensors between the input channels as per your suggestion, sensor B, which was not working well previously, is now working well and following the set point at a fixed ramp rate. While sensor A, which was sensing the temperature properly previously, is now not following the ramp rate and showing a higher temperature than the set point while cooling through the program and a lesser temperature during the warming cycle. The difference between sensor A and the setpoint continues to increase as the program runs further.
Sensor A is the control input for heater output, and no manual output percentage is selected.
I am not able to understand what the problem is.
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Post by remi1999 on Jul 12, 2024 1:04:02 GMT -5
Hey there, You should first check all connections to the temperature sensors and ensure they are secure. Test each sensor individually with a multimeter to see if they're functioning properly. Also, review the controller settings for any misconfigurations and look for error messages on the display. If the issue continues, consult the user manual or reach out to Lakeshore's technical support for assistance.
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at15
New Member
Posts: 5
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Post by at15 on Jul 12, 2024 22:03:22 GMT -5
Hello Sir @lake Shore Jeff M
I checked all the connections and tested each sensor as well. Temperature controller settings are also acceptable. I am wondering that a diode that was not sensing the temperature correctly is working fine after switching the controller input channel while the good diode is not working correctly in any channel.
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Post by Lake Shore Jeff M on Jul 15, 2024 7:50:27 GMT -5
Basically since the issue remained on Input B, this indicates that the Model 335 needs to be returned to the factory for a repair. Please contact the Lake Shore Support Department at support@lakeshore.com in order to arrange the RMA for the repair.
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at15
New Member
Posts: 5
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Post by at15 on Jul 15, 2024 8:10:51 GMT -5
We have a Lakeshore model 336 temperature controller as well. In this controller, also, sensor B is not sensing the temperature correctly. But when we switched the input channel in temperature controller 335, as per your suggestion, sensor B started working fine. How is this possible?
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Post by sassastatus on Aug 12, 2024 4:07:34 GMT -5
Temperature sensors measure the temperature of a substance or environment by converting it into an electrical signal. These sensors provide crucial data for maintaining desired temperatures. Temperature controllers, on the other hand, use this data to regulate heating or cooling systems. Srd Status check
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