Cable Length DI828
The datasheet of DI828 specifies maximum cable length of 200m for control voltage 120V AC.
However if I calculate the impedance of a 200m cable using the 100pf/m mentioned in the datasheet I get an impedance of approx 130kOhm allowing for the channel input resistance of 14.2kOhm and then using a simple voltage divider as an approximation this results in a voltage of 12V across the input.
Well below the 30V limit that is the threshold for a logical 0.
Only when I get to about 500m cable length does the voltage approach 30V
What am I missing?