Measuring voltage using ACPL-C87B, question about grounding

[mike buba]

Hi All,

I am thinking of using the ACPL-C87B for measuring inverter voltage (both DC and AC). In the technical manual, there is a typical application circuit (shown below).



Pin 4 is connected to the GND and the bottom side of the voltage divider.

However, if I am measuring line-to-line voltage (Vab, Vbc, and Vca), then in each of these cases, my 5V DC GND will be connected to the line voltage potential. Similarly, for DC measurements, with a grounded mid-point, the negative DC rail will be at -1/2 DC voltage.

Basically, my voltage divider schematics will look like this, with both L1 and L2 at the high(er) voltage, e.g., 230 Vac RMS and 680 Vdc, but the ACPL-C87B says connect analogue PCB GND to L2.



Is it possible to use the ACPL-C87B to measure AC voltages? And how should my connection between L1 and L2 and the input pins to the voltage sensor look?

Kind regards, MB

[ArdWar]

The two sides of the IC are galvanically isolated. You can pick any voltage (within isolation rating) as "GND1" and it'll be fine. One common challenge with isolated sensor like this here is how to supply VDD1 that is relative to GND1 while also galvanically isolated to VDD2/GND2.

Note that if you use multiple IC for multiple Phase-Phase measurement then each of their GND1 and VDD1 must also be isolated from each other.