BlueTherm Duo Temperature Discrepancies

968x601 Data Logging General

BlueTherm Duo Temperature Discrepancies

This issue was resolved in Roastmaster 7.0.1


Data Logging users using the Bluetherm Duo may, in some cases, experience discrepancies between the temperature displayed in Roastmaster and the temperature displayed on the Bluetherm Duo. This occurs when the Bluetherm Duo supplies its data to the app in the Fahrenheit scale, when Roastmaster is expecting the Celsius scale.

When Does This Happen?

Roastmaster operates internally in the Celsius temperature scale, translating probe readings to Fahrenheit for screen display and database purposes when curves are set to Fahrenheit.

Consequently, when opening a connection to a probe, Roastmaster issues a command to the Bluetherm Duo to supply its readings in the Celsius scale. The Bluetherm Duo, instead of switching to the requested scale as the documentation suggests, toggles its current setting from C to F or vice versa, resulting in a discrepancy every 2nd time this command is issued, and in those times, supplying a Fahrenheit number when Roastmaster is expecting a Celsius number.

When this bug presents, it will manifest in the Roast Console and Analyzer in the following ways:

  1. If your curve is set to Celsius, Roastmaster will display the number it’s given, which will be the Fahrenheit translation provided in lieu of the desired Celsius number.
  2. If your curve is set to Fahrenheit, Roastmaster will translate what it believes to be a Celsius number using a standard C to F formula, and display the result – in essence a Celsius temperature translated twice.

When Does This Occur

Since the Celsius command is issued to the Bluetherm Duo whenever a probe connects, this issue will result in the curve displaying the wrong temperature on alternating probe connections. Connections occur whenever Roastmaster needs to know the probe temperature, such as when viewing the probe details screen, the roast console or the roast analyzer.

Most users use 2 probes with the Bluetherm Duo. Because every second connection causes the Bluetherm Duo to come back into sync, it’s probable that users roasting with 2 probes are unaware of this issue. This is the reason it’s taken me a few weeks to pinpoint the cause.

If you make use of curve templates, and/or roast back to back batches, it’s also probable that you never physically disconnect from the Bluetherm Duo at all, so may have never seen this issue.

How do I work around this issue?

If the probes are reporting erroneous numbers in the roast console, simply exit out of the roast console, wait 15 seconds (unused probes will be disconnected), then open the roast console window again.

If you are using 1 probe, the curve temperature should then be in sync. If you are using two curves, both curves will have issued the Celsius command, causing it to come in sync, then immediately go out of sync again. In this case, you will need to delete one curve, and recreate it. The last probe connection should bring the Bluetherm Duo back into sync.

When Will This Be Fixed?

I don’t have any word from the manufacturer yet if this behavior is the intended behavior or simply a spot in the documentation that has been translated in a less than understandable way. Whatever the case, I have reworked the code so that Roastmaster will query the unit to determine the scale it’s given, and translate accordingly.

Until the update goes live, please inspect your curves before starting a roast. If all appears well, you can proceed normally. The probes will not disconnect in normal use for any reason other than a Bluetooth protocol error for the duration of the roast.

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