Gary Graham
TVWBB Fan
I am using an external thermocouple amplifier (Adafruit AD8495 Breakout) and am reasonably sure it is working properly, but not seeing the correct temps in Heatermeter.
The thermocouple breakout board is using 3.3v as the supply voltage. I got same results using the 5v supply, and decided to try the 3.3v... same results.
Individual component testing:
a) The thermocouple sends the proper temperature when connected to a DVM style thermocouple reader, validating the thermocouple is not fried.
b) I did a minimum config test with the Rpi with a 5v usb power source and the thermocouple breakout board connected. The HM board was NOT connected...
Measured the output pins of the thermocouple breakout board to be 1.361v using a DVM.... Compared to room temperature reading using the thermocouple jack on the DVM, which read 25.2 degrees C. (25.2 * .005) = 1.376 v
I have the thermocouple in a bundle with a Thermoworks meat probe and a ET-732 pit probe next to the fan output of a laptop.
The Thermoworks and ET-732 are within a couple of degrees of each other and reading 101-102 degrees F.
Heatermeter board Setup:
Lifted the "bottom" connection (as you would look at the LCD) for the food2 and food3 10K pullup resistors. This leaves the resistor hanging, but still connected on the +vcc side.
I used the menu page to select the probe type to be Thermocouple, and used the default value of 5mV/C.
With nothing connected to food2 or food3, the HM reports 34.5 degrees
With the thermocouple amp connected to the food3 position of J2, the HM reports ~695 degrees F.
So I played around with the mV/C setting to see if I could get the TC to read like my Thermoworks probe or the ET-732 pit probe... Those are on pit and food1, and set up as such in the configuration page.
Noticed that when I set the mV/C to 100, the HM will report the thermocouple temp to be ~108.8 degrees, and when I change the mV/C to be 99.999, the HM reported temp drops drastically to 57.6 degrees, and when I go back to the configuration page, the number I see for the mV/C is actually 99.998998.
Really odd stuff. Am I doing something wrong here ?
The thermocouple breakout board is using 3.3v as the supply voltage. I got same results using the 5v supply, and decided to try the 3.3v... same results.
Individual component testing:
a) The thermocouple sends the proper temperature when connected to a DVM style thermocouple reader, validating the thermocouple is not fried.
b) I did a minimum config test with the Rpi with a 5v usb power source and the thermocouple breakout board connected. The HM board was NOT connected...
Measured the output pins of the thermocouple breakout board to be 1.361v using a DVM.... Compared to room temperature reading using the thermocouple jack on the DVM, which read 25.2 degrees C. (25.2 * .005) = 1.376 v
I have the thermocouple in a bundle with a Thermoworks meat probe and a ET-732 pit probe next to the fan output of a laptop.
The Thermoworks and ET-732 are within a couple of degrees of each other and reading 101-102 degrees F.
Heatermeter board Setup:
Lifted the "bottom" connection (as you would look at the LCD) for the food2 and food3 10K pullup resistors. This leaves the resistor hanging, but still connected on the +vcc side.
I used the menu page to select the probe type to be Thermocouple, and used the default value of 5mV/C.
With nothing connected to food2 or food3, the HM reports 34.5 degrees
With the thermocouple amp connected to the food3 position of J2, the HM reports ~695 degrees F.
So I played around with the mV/C setting to see if I could get the TC to read like my Thermoworks probe or the ET-732 pit probe... Those are on pit and food1, and set up as such in the configuration page.
Noticed that when I set the mV/C to 100, the HM will report the thermocouple temp to be ~108.8 degrees, and when I change the mV/C to be 99.999, the HM reported temp drops drastically to 57.6 degrees, and when I go back to the configuration page, the number I see for the mV/C is actually 99.998998.
Really odd stuff. Am I doing something wrong here ?