Measurement Computing USB-TC, calibration date remains at 2015 after InstaCal A/D calibration just now (2022)

[bjorn_tt]

Hello Measurement Computing Support Experts,

We have at least 2 USB-TC modules here. For one of them (s/n 1ACEC6B), I tried to do the A/D calibration yesterday, using the InstaCal software. The window with progress bar suggested that it completed successfully. However, upon re-reading the configuration, the calibration date still comes up as 11/26/15 instead of 9/20/2022.

It would be helpful to know what the calibration actually does. Is it just copying of the coefficients (based on thermovoltage look-up tables) for the configured type of TC to the coefficient banks for the 8 channels? Is only a change in thermocouple type prompting a change in those coefficients and a new calibration date? Or is there actually some kind of measurement going on during the calibration?

 

Thanks,

Bjorn

[JRys]

Hello,

Inside the USB-TC is a known millivolt reference. During calibration the channels are first connected to ground to measure offset. Then they are connected to the millivolt reference and with the two values, gain and offset coefficients are calculate and stored. This allows it to measure the thermcouple voltage accuractely. 

During operation, it measures the thermcouple voltage, the CJC sensor and from these to values it determines temperature for the particular thermcouple type.

As for the calibration date, 11/26/15 is the last factory calibration date, which happens to be the manufactured data. I check, and this particular USB-TC has never been sent in for a factory calibration. One thing to keep in mind, the millivolt reference used in the self calibration does eventually drift. The factory calibration reset the reference so that future self calibration are accurate. The current price for a calibration is $62.75 plus shipping. Email your contact info and model/serial number to info@mccdaq.com to receive a quote.

Best regards,

John