Can leakage voltage affect 7550/7650 digital inputs?

Goals and Symptoms

In certain cases a device that is connected and triggering the digital inputs on an ION7650 or ION7550 can have a leakage voltage. A leakage voltage is occurs when a device produces a certain amount of voltage across its terminal when it is open (ideally the value should be 0 volts).
In the case of a device triggering a digital input: when the device closes the circuit the digital input registers a trigger, and when the same device opens the circuit the digital input should not be registering a trigger.

But in the case of a voltage leakage (when the triggering device is open) some testing is required to determine the results.

Facts and Changes

Keywords:
input doesn't open
leakage voltage
ION7650
ION7550
switch
digital input
closed
swap
change state

Causes and Fixes

The internal resistance between the Scom and S8 or S7 in the diagram below is 230K, while on the old 7550/7650 (before September 2009) meters it was 40K.

The minimum amount of current required for the meter at the digital inputs to register a pulse is 50 micro A.

Hence with this information, figure out if a leakage voltage across the digital input connection is enough to produce a 50 micro ampere current. If the leakage produces a 50 micro ampere current or more work out the circuit to reduce the current.

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Legacy KB System (APS) Data: RESL199691 V1.0, Originally authored by MiNe on 08/22/2009, Last Edited by MiNe on 08/22/2009
Related ranges: ION7550/ION7650