Enhancing Input Voltage Range of the AD2

[damayn]

Hallo all,

 

for a power electronics project I have to work with bigger voltages than the AD2 can work with. 

As a solution for the problem i was thinking about a simple voltage divider to GND, one at the positive and one at the negative input and zener diodes as additional overvoltage protection. Is this a valid proposal and is there something I should be careful with apart from resistor values and input impedances? Would love to hear some feedback.

[Guest]

The problem with your proposed approach is that the voltage divider would usually influence the circuit you're trying to measure.

A good way to prevent that is to put an op-amp between the thing you're measuring and the AD2. If done right, the circuit doesn't notice the opamp (as it has near-infinite input impedance), and you can use appropriate resistor values to scale the voltage you're expecting to see in the circuit to the range of the AD2.

The AD2 provides V+ and V- supplies that can be used to power the opamp.

To pick the right op-amp, you will need to consider the bandwidth of what you're trying to measure. If it's anywhere high, you will have to use a more advanced op-amp, but for low-frequency signals, essentially any opamp will do.

[attila]

Hi @damayn

For input attenuation you could try high voltage series resistor (+trimmer), 1-9M for 2-10X probe.
Protection diode is recommended since the device is rated to 50V.

See the following posts: