May be it a simple question… but how to determine the resistance value (Om) that should be used between A1 and GND in case of measuring voltage via analog input 1 that more than 5V. (for example the range is: 0 … +30 or -30 …+30)? What the formula should be used for it?
You have to use series resistor between the voltage (e.g. +30V) and A1 input.
A series resistor 500k gives you the range to +30V.
A series resistor 100k gives you the range to +10V.
You can’t measure negative voltage with the K8055.
