Configuring Relays with GMP250 Software Version 1.2.9 - GMP251 - GMP252

Relay Box for GMP250 Carbon Dioxide Probes Quick Guide

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English (United States)
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User guide
Use the rsel command (not the asel command) to set the analog output channel to current (mA).
  1. Connect GMP251/GMP252 to a computer with USB service cable 242659 and open a terminal connection (for example, PuTTy).
  2. Enable advanced configuration commands with the pass 1300 command.
  3. Set the serial mode of the analog current output channel (2) to relay control with the following command: smode relay2
  4. Configure the current output channel's relay settings with the rsel command:
    rsel [channel parameter release_ppm set_ppm set_value error_value]
    • channel= analog output channel: set to 2 (current)
    • parameter = the parameter that controls the relay: set to co2
    • release_ppm = CO2 ppm level at which the relay is released
    • set_ppm = CO2 ppm level at which the relay is activated
    • set_value = the current output (mA) when the relay is activated: set to 12
    • error_value = the current output when the probe is in error state
    The relay mode of GMP251 and GMP252 probes has been designed to use 12 mA as the relay control current. Use only 12 mA for the set_value configuration when using the relay box with GMP251 and GMP252.


    Set the analog output channel 2 (current) to control relay operation with the following settings:

    • The relay is activated when the measurement is over 10100 ppm CO2 and released when under 9900 ppm CO2. Setting these relay activation limits means using a 1 % CO2 (10 000 ppm CO2) relay setpoint with a hysteresis of ±1 % (100 ppm CO2).
    • The output current is 12 mA when the relay is activated.
    • The output current is 0 mA when the probe is in error state.

    Enter the following commands:

    pass 1300
    smode relay2
    rsel 2 co2 9900 10100 12 0