Any current sense amps that can handle 0V on one side of shunt?

Which amps are your looking at and what does you're circuit look like.

not clear on what your mean for 49.95 to 50 on two sides?

Since resistors for a brushless motor using 6-step should be between the source pins of the low side fets and power return.

I am using a brushless motor driver. It has a motor supply input, and then outputs for the coils. I do not want to just measure current (on the input of the motor controller) as I want directional information. So instead, I plan on looking at individual coil currents. So, I plan on putting shunt resistors on each wire to the motor. Sometimes those shunts will be on the high end, and other times they'll be on the low end. Thus I need a device that can handle both. Currently I'm looking at using the Analog AD628 or AD8210.

-Michael

I dont thinkg you will get directional information if its a true 3 phase brushless motor. What makes the motor change directions is the phase sequense which the windings are energized. (say for forward it 1,2,3 and for backwards its (3,2,1).

You can do that by looking at the current in two phases. instead of just one.

The problem with using a instrument amp is that the common mode signal (motor phase voltage) will be very large with lots of high frequency edges. Compared to the signal you're trying to measure this is huge. You should put some common mode noise filters before going into the instrument amp. Then you'll be fine.

you might consider something like this instead of the currents are in the 1 A range.

you might consider something like this instead

that's a tough ask.

non-contact sensors may work better, either current transformers or hall-effect current sensors.

Bye. Jasen

Nominally, yes; they're called isolation amplifiers (and are expensive). If the sense of the current is unipolar, you can make a current mirror and level-translate the mirror current to a convenient (-12V?) power supply. A current mirror with sense resistor, scale resistor, op amp, and MOSFET can be accurate and easy to build, but a true-differential instrument amp with that much common mode range is a challenge. The op amp for the mirror has to operate over the full 0 to 50V input range, though.

LTC 6103 is a dual IC that does this; no experience with it, but it seems appropriate

That device requires a minimum of 4V on the inputs. It's a high side current amplifier. I need something that can be both high and low side.

-Michael

That device appears to be limited to a minimum current of 5A. I need to be able to sense lower currents than that. I need to be able to sense about -25 to 25A.

-Michael

Oops - looks like I misread the specs. that looks like a viable candidate. The output goes a little higher than I'd like (it'll be going into a 3.3V part - I will have to see if the ADC can handle a 5V vref)

-Michael

Take a closer look. That particular device work has +/- 5, +/- 20 and

Robert