ML-OO-SW – Option board

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Adds three galvanic isolated switches with potential free contacts

An ML-417 data logger is standard provided with one digital output, an open collector alarm output to switch on an actuator/relay in case a parameter value is outside its limits (e.g. a high water level).

You can use the ML-OO-SW board to add three more digital outputs, in case you need more than one digital output or want to switch on an actuator/relay to prevent an alarm situation (e.g. to switch on a gasoline generator as backup for a solar or wind turbine powered installation to avoid a power outage).

A switch can be activated in steady state or pulse mode (V1.06 and above)

Additional information

About these switches

The three switches are galvanic isolated from the ML-417 as well as from each other. The switches have potential free contacts and therefore acting like ordinary wired switches. The switches don’t need a voltage to operate and they don’t have a positive or negative terminal, so you could switch on a DC as well as an AC circuitry as long as the connected voltage does not exceed ±100V and the current through the contacts does not exceed ±200mA.


  • Switches: 3
  • Activation modes: Steady state or pulse mode (V1.06)
  • Activation delay (V1.06): up to 4095s
  • Pulse width (V1.06): 1 to 4095s
  • Pulse interval (V1.06): Once or 2 to 4095s (max 0.5Hz)
  • Protection: Galvanic isolated
  • Contacts: Potential free
  • Connected voltage: 100V maximum
  • Contact current: 200mA maximum
  • Power consumption: 15uA in steady state sleep, 0.5mA during active pulse (train)
  • Timing accuracy: <=20ms per second (<=2%)


The ML-417 can be configured to regularly, e.g. after a sensor reading session, update the state of a switch channel.

  • A switch channel will be set to active when the value of the correlated data logger parameter equals or exceeds 0.7 and released when it equals or falls below 0.3
  • The best way to activate switch channels is by using calculated channels evaluating to 0 or 1 (See: example below)
  • Only values of parameters, up to 3, with their “data output flags” set to the auxiliary output board will be used for updating the state of the switch channels.
  • The value of the first parameter will be correlated to the first switch and so on, the order of parameters can be organized through the “Parameter overview”-menu of the ML-417.
  • The physical switch will be activated after the expiration of the set activation delay following a switch channel transition from 0 to 1 and be deactivated at a transition from 1 to 0 or when the set pulse width has expired (See: diagram above)
  • After changing channel timing, the current active pulse train will stay active till a next channel transition
  • Attention: Avoid using long lasting pulse trains due to increased power consumption and time drift due to microprocessor oscillator accuracy


Assume you have:

  • An irrigation pond that can be replenished by natural sources (e.g. rain) or a paid source and you want to avoid reaching a critical level and paying to much.
  • The critical LEVEL of the pond is 2m and the conditional replenish level 2.5m
  • The supply pump capacity is 4m3/h
  • You only want to use the paid source:
    • When the pond reaches its critical level or
    • When the pond reaches the replenish level and the 24h rolling average of the irrigation FLOW exceeds 2m3/h (50% of the pump capacity).

Steps to take:

  • Use an aggregated channel to evaluate FLOWAVG from FLOW by specifying an aggregation period of 86400 seconds
  • Use a calculated channel that evaluates FLOWAVG and LEVEL to 1 in case the supply pump should be switched on and 0 when it should be switched off
  • Correlate and order the calculated channel to a switch by setting its “data output flags” to the auxiliary output board

Formula: le(:LEVEL;2.0;1;le(:LEVEL;2.5;ge(:FLOWAVG;2.0;1;0);0))


  • If :LEVEL lower than or equals (le) 2m return 1 to start the pump
  • If :LEVEL lower than or equals (le) 2.5m check the flow, else return 0 to stop the pump
  • If :FLOW greater than or equals (gt) 2m3/h then return 1 to start the pump, else return 0 to stop the pump

Discover the possibilities

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