Talk to fellow users and Lake Shore experts

Lakeshore 325, new cernox sensor

new

« Prev
1
Next »

angel6700
New Member

Posts: 1

Lakeshore 325, new cernox sensor Jul 27, 2020 3:23:16 GMT -5

Quote

Post by angel6700 on Jul 27, 2020 3:23:16 GMT -5

Hello,
We have several lakeshore temperature controllers and sensors.Most of the sensors we buy are calibrated, but recently we bought a couple of non calibrated ones.We have tried to calibrate them by measuring its resistance in channel B by means of the lakeshore 325, while recording the temperature in channel A by using one of the calibrated sensors.
The problem arises when we reach temperatures below 4K, that resistance increases so much (above 7000 Ohm) that the controller is not able to measure.
What can we do?
We expected to be able to calibrate our sensors, and we are able to ramp our temperature down to 1.8K at rates < 1K/min

Thanks in advance.

Angel

Lake Shore Jeff M
Lake Shore

Posts: 294

Lakeshore 325, new cernox sensor Jul 27, 2020 7:13:23 GMT -5

Quote

Post by Lake Shore Jeff M on Jul 27, 2020 7:13:23 GMT -5

As you have discovered and as identified in the specifications of the Model 325 Temperature Controller, the maximum resistance that the Input can read is 7500 ohms, therefore, it is not possible to use the sensors you have with the Model 325 Controller once they exceed 7500 ohms.

The only way to complete a calibration below 4K would be to use a separate 10uA Current Source and Multimeter to measure the resistance once it exceeds 7500 ohms. Keep in mind that the Model 325 would not be able to read the temperature once the resistance exceeds 7500 ohms and would indicate a S. Over error when that condition existed. Other Controllers like our Model 332, 335, 336 and 350 will read up to 100K ohms so you could use one of those to complete the calibration and use the sensor below 4K.