I am building four 30v voltage sensing circuits to measure battery+/battery-, load+/load-, battery+/load- and battery-/load+ voltages to verify contactor open/closing sequence.
- V1 is 30v battery
- Load will be DC motor switched by 2 contactors, now im just using a open circuit to do testing.
- The monitoring circuit can use battery negative as circuit GND, but I prefer not because I dont want connect low voltage side to high voltage side.
- The circuit will be powered independently of battery because of above reason.
- Schematic above only shows battery+/battery- and load+/load- sensing circuits.
When sw1 and sw2 are both open or closed, I got expected results (1.99v at outputs with 0.066 gain). However, when sw1 is open sw2 is clsoed (or sw2 is open s1 is closed), I see a weird 0.66v at output 1 while output 2 is 2v. What would be the reason?