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trying to connect MP730424 DMM with rs232 but get Timeout error

JeremieWerner

I am trying to remote control a DMM MP730424 from a computer with Windows 11. *IDN? gives a VI_ERROR_TMO: Timeout expired before operation completed.

the instrument port information show: baud 115200, parity None, stop bits 1, data bits 8. 

What is the expected EOL and termination character?

has anyone manage to control this device via RS232?

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  • 0

    Which USB to RS232 adapter are you using - if the DMM uses true RS232 it may very well not work with a logic level adapter.

    Do you have a scope (ideally with RS232 decoding) - if so then connect it to monitor the RS232 RX and TX pins.

    Found some more info here:

    https://github.com/PetteriAimonen/owon-xdm2041-info/tree/main/mcu_board

    This would suggest that the DMM is  a logic level RS232 so it won't work (reliably) with a a true RS232 adapter on the PC.

    You can check this - disconnect the lead from the DMM and use another meter to measure the voltage on pins 2 and 3 relative to pin 5.

    If all the voltages you see are between 0 and +5V it is a logic level interface.

    If at least one of the voltages is more than 3V  -ve  it is a true RS232  interface,

    If both voltages are less than +/-0.5V is not a functional interface.

    There are some more tests that can be done with a meter to check that you have RX and TX  correctly connected to their complements on the pC lead but we'll leave that until we know if we have the right voltage levels.

    MK

  • 0 in reply to michaelkellett
    michaelkellett said:
    This would suggest that the DMM is  a logic level RS232 so it won't work (reliably) with a a true RS232 adapter on the PC.

    Looks like there is a Sipex SP232 RS232 line driver/receiver on the circuit board.


    image

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