Herpstat Thermostat Problem

So what is the actual temp inside the tub on the back wall? Have you confirmed your readings with a different thermometer?

yes, sorry

The best thing to do would be to test the probe accuracy. Remove the thermostat for service briefly for the test (disconnected your rack). Tape a couple of your thermometer probes together with the Herpstat Probe at the tips. Then monitor the temps with the probes just hanging in the air. Give it about 5 minutes to stabilize. The acurites can be a couple of degrees off and still be in spec. The Herpstat probe will be more accurate as they have a +- .9 degree accuracy from the manufacturer of the sensor. You should get a good idea at that point if you have a acurite that is out of calibration or something is wrong with the Herpstat probe. If they are a couple of degrees off you can use the sensor matching option of the Herpstat to match it to your acurite thermometers.

Another way to look at it...
Say the actual temp is 85 degrees
That means the Herpstat probe can be 84.1 to 85.9 and it is still in spec.

Digital thermometers like the accurite are typically +- 2 degrees. So that means it can show 83-87 degrees in spec.

Then if you compare the Herpstat and accurite at their opposite ends that mean the acurite could show 87 and the Herpstat 84.1 and technically both are still in spec.

Dion Brewington
Owner, Spyder Robotics

Originally Posted by spyderrobotics

The best thing to do would be to test the probe accuracy. Remove the thermostat for service briefly for the test (disconnected your rack). Tape a couple of your thermometer probes together with the Herpstat Probe at the tips. Then monitor the temps with the probes just hanging in the air. Give it about 5 minutes to stabilize. The acurites can be a couple of degrees off and still be in spec. The Herpstat probe will be more accurate as they have a +- .9 degree accuracy from the manufacturer of the sensor. You should get a good idea at that point if you have a acurite that is out of calibration or something is wrong with the Herpstat probe. If they are a couple of degrees off you can use the sensor matching option of the Herpstat to match it to your acurite thermometers.

Another way to look at it...
Say the actual temp is 85 degrees
That means the Herpstat probe can be 84.1 to 85.9 and it is still in spec.

Digital thermometers like the accurite are typically +- 2 degrees. So that means it can show 83-87 degrees in spec.

Then if you compare the Herpstat and accurite at their opposite ends that mean the acurite could show 87 and the Herpstat 84.1 and technically both are still in spec.

Dion Brewington
Owner, Spyder Robotics

Is there not a way to ohm out the probe and compare the reading to a chart? That would be a faster way to test the probe..

No ohms, digital probe.

Ahhhh makes sense thanks for that info..