How to offset my temperatures (temperature deviation)

This article will help you troubleshoot when temperatures in Cropster are not accurate in comparison to the readout on your roaster.

In general

• A slight deviation (up to 2°C/4ºF) can be normal depending on your setup (see below).
• If the deviation is static (stays the same throughout the roast), an offset can be added within the RI preferences.

Cropster Connector

If your roast machine is connected with the help of a Cropster Connector (Phidget), we have to differentiate how the probes are connected to the Cropster Connector. 

• Splicing connection
• Dual probes

• Independent probe next to existing probe

Splicing connection

There are many potential error sources when setting up a splicing connection.

The first step is to re-do the splicing connection. The wires have to be twirled very firmly. If they are too loosely twirled, a deviation is very likely. 

Dual Probes

A dual probe has two temperature sensors in the inside. One sensor is connected to the two leads that go into the machine's readout and one sensor is connected to the two leads that go into Cropster. 

Since there are two sensors measuring the temperature independently from each other, the temperatures are not completely aligned. A deviation of +-2°C/4ºF is likely.

Independent probe next to existing probe

When there is an additional probe next to an existing probe installed, a deviation is very likely. There are two independent sensors measuring the temperature.

The following variables can have an impact on the deviation:

• Probe placement
• Sheath thickness
• Batch size
• Probe age

Countermeasures 

Probe type

Is the type of the probe correctly assigned within the RI?

Check the ends of your thermocouple wires. From the colored coating of the wires you can deduct the type of thermocouple.

The physical connection

Make sure all wires are connected correctly. The thermocouple leads have a positive and negative wire. Ensure that all positive wires are connected with each other and go into the positive port of the Cropster connector, and the same for the negative wires. 

Static vs. dynamic deviation

Static deviation

When the deviation is static, meaning the difference in temperature stays the same throughout the roast, an offset can be added.

1. Go to Account > Preferences > Machine tab
2. Add the difference in temperature to the offset field under the affected temperature measurement.
   

Dynamic deviation

When the deviation is dynamic, meaning the difference in temperature varies throughout the roast, focus on one readout only - preferably the Cropster readout.