PicoScope 7 Software
Available on Windows, Mac and Linux
TC-08 offset error using Raspberry Pi
TC-08 offset error using Raspberry Pi
Have been using a TC-08 for over year, connected to a laptop. Data all comes in fine, readings are correct and there have been no issues. Picolog 6.2.8 being used without issue. Only one thermocouple, a type-K was being logged.
Last week we decided to try a Raspberry Pi in place of the laptop. Since doing so our readings have become strange. The TC-08 and probe have not been touched, just the USB cable has been moved from the laptop to the Raspberry Pi. The laptop and Raspberry Pi power supply are both connected to the same strip plug, the Pi is using the OEM USB-C power supply.
By strange I mean the following; previously we would see a constant temperature of around 10 degC. Now, during the same period of operation we are 'seeing' 20 degC according to the logged data in the Raspberry Pi but this is clearly wrong as other sensors tell us the temperature has not changed.
The shape and characteristics of various temperature changes remain the same or similar, but they are now consistently offset.
I have read quite a lot about grounding and plan to attempt to ground the USB-C power supply cable and/or a ground pin on the Raspberry Pi. In the meantime though, has anyone else had similar experiences?
I have tried both USB sockets on the Raspberry Pi; no change in the problem.
How is it that when using a laptop to power and log data from the TC-08 it works fine, but using a Raspberry Pi for the exact same logger and probe, and also running Picolog 6.2.8, different temperatures are recorded?
My issue would appear to be the opposite of this: topic28891.html?sid=
Last week we decided to try a Raspberry Pi in place of the laptop. Since doing so our readings have become strange. The TC-08 and probe have not been touched, just the USB cable has been moved from the laptop to the Raspberry Pi. The laptop and Raspberry Pi power supply are both connected to the same strip plug, the Pi is using the OEM USB-C power supply.
By strange I mean the following; previously we would see a constant temperature of around 10 degC. Now, during the same period of operation we are 'seeing' 20 degC according to the logged data in the Raspberry Pi but this is clearly wrong as other sensors tell us the temperature has not changed.
The shape and characteristics of various temperature changes remain the same or similar, but they are now consistently offset.
I have read quite a lot about grounding and plan to attempt to ground the USB-C power supply cable and/or a ground pin on the Raspberry Pi. In the meantime though, has anyone else had similar experiences?
I have tried both USB sockets on the Raspberry Pi; no change in the problem.
How is it that when using a laptop to power and log data from the TC-08 it works fine, but using a Raspberry Pi for the exact same logger and probe, and also running Picolog 6.2.8, different temperatures are recorded?
My issue would appear to be the opposite of this: topic28891.html?sid=
Re: TC-08 offset error using Raspberry Pi
This appears to be resolved by earthing the USB plug outer metal sleeve to the earth of the equipment cabinet. Not ideal, but clearly it shows there is an earth related issue. See picture below/attached showing the change in signal when the earth wire is added. Note the cold junction channel (purple) does not change anywhere near as much as the green channel ( the thermocouple ) or the red channel ( channel with nothing plugged into it )
- Attachments
-