sp
New Member
Posts: 1
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Post by sp on Aug 1, 2024 16:26:17 GMT -5
Hi there,
With the Lakeshore 321 auto temperature controller, we set the temperature to 20 K, however, the heater stops at 19.3 K. It still reflects 100% and HIGH on the display. Even if we try setting the temperature above 20 K, it stops at 19.3 K. A couple of months, it would remain at 20 K and we could go beyond 20 K. We are not sure if the heater is damaged or there is a problem with the controller.
Could you please provide your advice on how we can proceed?
Many thanks,
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Post by Lake Shore Jeff M on Aug 2, 2024 7:25:08 GMT -5
The Model 321 was designed to provide 25W of heating power by sourcing a 1A current into a 25 Ohm heater. The output will stop increasing when the current reaches 1A or when the Voltage is 25V. If you measure the voltage across the dual banana plug that the heater is connected to when the output says it is at 100% and you read 25V than the controller is working correctly and 25W is not enough to heat the sample space it is connected to. If you read less than 25V then the current is being limited to 1A and the heater is not a 25 ohm heater.
the first thing I would do is disconnect the dual banana plug from the 321 and measure the resistance across the prongs of the plug looking toward the heater. It should read 25 ohms. If not then the 321 cannot source the 25W of power. Let me know the result of your voltage and heater measurement and I will see what help I can offer
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Post by nitikaparashar24 on Oct 16, 2024 13:24:08 GMT -5
Hi Jeff, I am facing a similar issue where I set the temperature setpoint to 40 C but it reads 24.5 C only. The heater is at LOW 100 %. The stage I am trying to heat is at room temperature. I checked the resistance is 0.6 M ohms. The voltage is 29 v. What can I do to rectify it?
Thank you.
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Post by Lake Shore Jeff M on Oct 16, 2024 14:51:38 GMT -5
If your heater is actually 0.6 Meg Ohms, I am surprised that the heater is running at all. I do not know what the limitations were for the heater resistance; however, I am surprised it is not shutting off.
The low range of the Model 321 only supplies 2.5W of heating power so that may be why you cannot reach 40K
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Post by nitikaparashar24 on Oct 18, 2024 8:33:31 GMT -5
I also tried to operate it at High range, but it still doesn't heat up. Is there a setting I could change to check the fault in the system?
I am not sure if this is relevant but I had to bypass the switch as there was some fault in it and the controller wasn't turning on. The switch was supplying 12 V instead of 120V to the system so I bypassed it directly supplying 120V from main power source to it. Fuse is still intact and included in the circuit. Pls let me know what you think.
Thank you.
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Post by Lake Shore Jeff M on Oct 18, 2024 13:08:40 GMT -5
The Model 321 output has a 1A or 25V compliance setting. You can measure the voltage across the dual banana plug with the heater on high at 100% output to see what it is reading. If it is zero, then the controller is bad. If it is 25V, then it has reached its compliance value and the heater resistance is too large for it to produce the proper wattage. If it is somewhere between zero and 25V then it most likely is limiting the current to 1A and not producing enough power to heat the sample.
If the reading is zero, we no longer offer repair service for the 321 so you would need to replace the controller with one that is working.
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