Activity Forums Questions & Troubleshooting 24V 4-20mA industrial temp sensor, how to connect/read? Reply To: 24V 4-20mA industrial temp sensor, how to connect/read?

  • Friedl

    Member
    April 4, 2021 at 4:00 pm

    You need to give the sensor “space to breath” (=enough voltage left), otherwise it just won’t work.

    If you take this setup (from the product page):
    https://www.calex.co.uk/site/wp-content/uploads/2020/01/pyromini-oem-connections-4-20-ma-1024×411.png
    and add the 500 Ohm resistor across the +/- of the instrument shown in the picture, which would then be your Controllino, we can conclude:

    1. 0,020 A * 500 Ohm = 10V
    2. 0,004 A * 500 Ohm = 2V
    3. 24V – 10V = 14V > 8V ! (24V power supply assumed)

    And BTW (see datasheet):

    Max. Loop Impedance
    900 Ω (4-20 mA output)

    Put aside your Controllino, only leave the resistor, take a digital multimeter and verify your setup first. When you know what voltages are to be measured, verifying what you measure with the ADC is much easier.

    • This reply was modified 1 month ago by  Friedl. Reason: Stray DIV tags from the editor again. (PLEASE FIX THIS)