PT104 Resistance to Temperature Conversion

Hello,
i'm currently using a PT104 for temperature measurements using a PT100. However, since i'm using the Ethernet protocol, i need to convert the resistance value into a temperature value. The user's guide provides the formula for the resistance as a function of the temperature, and i need the inverse function. I was searching in the software usbpt104con.c in the folder /opt/picoscope/share/doc/libusbpt104 for the conversion formula but i didn't find it anywhere. Can you please write the exact formula to convert the PT100 resistance value into a temperature value?
Thank you very much, best regards
LM.

Hi Luca,

The measurement data returned is a 4-byte number which has to be converted into a resistance value.

You will need to use the lookup table information in Section 5 of the Programmer's Guide to map the resistance to a temperature.

Regards,

Thank you for the answer. I convert the 4 measurements into a resistance value but i cannot use the table for an online resistance-to-temperature conversion. Can you provide me the analytical equation used in your software usbpt104con.c? That would be the inverse equation of the one in section 3 of the PT-104 user's guide. Thank you for the help, best regards
LM.

Hi Luca,

You should be able to find the equation from the Standard resistance thermometer data section of the Wikipedia Resistance Thermometer page.

If you are able to use the driver API functions then the driver will convert the resistance to a temperature for you.

Please note that Pico Technology is not responsible for the content of external sites.

Regards,

Thank you for the help, one can use also the PT100 standard conversion equation written at this page:

http://www.code10.info/index.php%3Foption%3Dcom_content%26view%3Darticle%26id%3D82:measuring-temperature-platinum-resistance-thermometers%26catid%3D60:temperature%26Itemid%3D83

Following your manual the conversion has to be performed using the ITS-90 scale on a PT-104.
Best regards,
Luca Minzoni.