Vansco VMM3120, User Manual

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User Guide 11
Inputs
3.1.1.1. Digital Input Capabilities
The following table provides specifications for the VMM3120's digital inputs:
Digital Input Specifications
Item MIN NOM MAX UNIT
Input voltage range 0 - 32 V
Pull-up/pull-down resistance (24 V system) 2.8 k - -
Ω
Minimum negative going threshold 1.56 - - V
Maximum positive going threshold - - 3.65 V
Cutoff frequency (hardware) - 170 - Hz
Over-voltage - - 36 V
Wetting current - - 10 mA
3.1.1.2. Digital Input Configurations
Digital inputs are configured as active high by using pull-down resistors internal
to the module.

The input is configured as active high, an internal pull-down resistor is used,
and the input will be active when it is switched to battery voltage.
All digital inputs have their wetting current configured according to the
following:
Note: A digital switch (typically connected to a digital input) usually requires
wetting current (a small current that burns off contact oxidation when it is
activated). The amount of required wetting current required is based on
battery voltage and on the value of the pull-up or pull-down resistor.

Wetting current is determined by the value of the resistor. The maximum
allowable wetting current in the VMM3120 is 10 mA. Wetting currents
greater than 10 mA must be incorporated using resistors embedded in the
system harness.
The diagram in the Digital Input Installation Connections shows the configuration
for the digital inputs.