Hi @HeavyIron ,
Welcome!
The ACS37800 is designed to measure high load currents in power systems. It may not be the best choice or may be overkill if you only want to measure voltage.
For the voltage measurement, it depends if you are using GND or LO as the reference. With GND as the reference, a RSENSE of 8.2K delivers 245mV with an input of 60V: 60 * 8200 / 2008200.
The LO pin and extra 2 x 1M resistors are only needed if you need additional isolation:
Maybe, for your application, you do need the extra isolation the LO pin would give you? I’m not sure… If you do use the LO pin as your ground reference, then, yes, you could measure voltages up to 120VDC. But the SparkFun product is not designed to used above 60VDC. Just to be clear:
It is not clear to me if you are measuring true DC, or actually rectified AC? Half wave rectified, or full wave? That said, I’m wondering if a simple 4-channel ADC could work better in your application? Would you be happy adding your own voltage divider resistors? If you are, then you could use a single ADS1015 ADC plus a DataLogger to log four voltages simultaneously. But please be careful with your grounds. It is not clear to me if it would be safe to have all four voltages plus the DataLogger sharing a common ground. Maybe you need optical isolation?
I will include a link to a similar discussion about voltage measurement below. I hope it helps.
Best wishes,
Paul