Measuring voltage external 48VDC PS, without sharing ground

I have a question regarding the use of an Arduino board to measure voltage of a DC-powersupply without sharing grounds. So there should be a galvanic separation between the circuitry of the Arduino and the 48VDC-powersupply. A friend of mine told me to use the LM321 (Voltage to frequency converter, use the generated pulse-train for Arduino to measure and calculate corresponding voltage) but it can't handle a voltage in excess of 40 VDC. The next problem is, that if the LM321 circuitry uses the same powersupply as the supply it needs to probe, the frequency-value doesn't change when the voltage drops. So how am I going to monitor the output voltage of a 48VDC powersupply with an Arduino, without sharing a common ground? Thanks for your help in advance!

Use a voltage regulator on the LM321 to run it at lower than the voltage you are trying to measure. Then use a potential divider to feed a fraction of the voltage to measure into the chip. Then couple the output of this chip through a transformer or opto isolator into the arduino.

When the precision is not so important you may simply use an opto-coupler. You have to calibrate it as it is not linear.

There are chips designed for dealing with floating power supplies that can provide ISOLATION.




The voltage transducer is pricy, since it has only industrial grade, no consumer grade voltage transducer.