How to troubleshoot temperature deviation (Phidgets setup)

This article examines potential causes for temperature deviation between your roast machine and Cropster when connected via a Cropster Connector or Phidget.

To troubleshoot a deviation one has to distinguish between a minor deviation which can occur naturally (depending on the setup), or a major deviation which might indicate a setup error.  

Minor deviation (< 5°C/9F)

A minor deviation, up to 5°C/9F, can be normal depending on the setup.

Potential causes for a minor deviation are a splicing connection or sensor setup. 


A splicing connection can affect the potential being measured by the Phidget to calculate the actual temperature which results in a small deviation.

If the deviation stays the same throughout the roast, an offset can be added to Cropster. 

Alternatively, we recommend to focus on the Cropster temperature readout only and ignore the deviation. 

Sensor setup

When installing an independent probe connect to Cropster, a deviation is very likely. Depending on where the newly added probe is placed, the temperature deviation can be bigger or smaller. The temperature can vary a lot inside the drum.

The best results can be achieved when installing an independent probe right next to the existing probe and making sure both probes have the same specifications (type, length, diameter). 

Also with dual probes, a small deviation is possible. A dual probe carries two independent sensors within the probe hull which measure the temperature independently from each other.

Generally, we recommend to focus on the Cropster temperature readout only, as Cropster is the tool you are developing the profiles with.

Major deviation 

A major deviation is a difference of more than 5°C or 9F between the roast machine's readout and Cropster. 

The causes for a major deviation can vary. Deviation may be caused by, but not limited to:

Physical connection

A deviation is often the result of a splicing connection set up incorrectly or wires connected to the wrong Connector port.  

The thermocouple cable consists of a negative and a positive wire and which need to be spliced or connected to the Cropster connector accordingly. 

The negative wire needs to be connected to the "G" port and the positive wire to the respective number port (as shown in the example of a K-type thermocouple connected to a Cropster Connector below).

If a splicing connection is set up, negative wires and positive wires need to be connected with each other to ensure an exact readout. Verify that the two leads from your probe wire have been spliced with the corresponding leads from the splicing wire according to polarity (+ to + / - to -).

Warning: disconnect the USB cable from the Phidget/Cropster Connector and turn off your roast machine while you check the splicing connection.

Roasting Intelligence (RI) configuration

A deviation can occur if the type of thermocouple has been entered wrongly in the RI settings. Cropster supports thermocouples of type J, K, T, and E. 

Make sure the thermocouple type within the machine settings (Account > Preferences > Machine tab) is assigned correctly.

Learn how to identify the probe type

Further assistance required? 

Please create a support ticket by emailing to and provide the following information:

  • A general description of the problem (how big is the deviation, is it static or dynamic, etc.)
  • Attach the RI log files (to be exported via Help > Export log files)
  • Pictures of the physical connection (of the Cropster Connector, the thermocouple wires, the splicing connection, etc.)