I am already using the AD627 that I find fantastic for example strain gauge measurement.
Now, my problem is to measure a current through a shunt of max 70 mV.
It is a PWM signal, thus, the information is a pulse where frequency is stable but the modulation is not.
Therefore my output is also a pulse, what I can not use because I need a DC information, not a PWM one.
So, is there a special schematic / add/ filtering / else that I have forgotten ?
In summary, I have a shunt before the load that works in PWM mode. I want to measure the current and get a DC voltage. Possible with the AD 627 ?
Thanks for your help
Sounds like all you'd need to do is to use a low pass filter (LPF, simple RC) on the signal in order to derive a DC voltage that's proportional to the PWM duty cycle and you'd have what you need
Because of AD627's high input impedance, you may be able to configure your LPF right onto the input of the AD627 after the shunt. You can use the AD627 Spice model to make a pretty good prediction of the circuit behavior.
I wonder what they mean this bipolar pulses on second image?
Thanks to both of you for your guidances. I will try it and hope that I will be a good practicer...smile. Kirik, the first image is the voltage from IN+1/Ground.The second image is the IN+/IN- image with IN1 is the ground. The voltage is taken from a shunt of 70mV/200A just before the load.
You are great, I appreciate your help both of you.
Will keep you informed.
Regards to all
I have succeeded to make it working with a RC filter after the output of the AD627. This one is a real exceptional amplifier. Thanks to everybody for the idea about the RC.
Now, my friend, make me a favor and tell me if you know a AD627 that could have an input in a range of 0-30V. I work on a automotive application and as you know, alternators could go up to 28V-30V depending on the truck.
AD627 is for a current sens PWM 1KHz measuring 100A - 35 mV.
So, any idea for a "AD627" like for a voltage inputs in a range of 28V-30V ? I tried to find it on the website, nada..
I have tried to put the sense shunt down, but at 35 mV, it is a soup, noisy and the RC is not effective at all.
Regards and merci beaucoup !!
As far as I understand, you use shunt in positive supply rail and you need INA which can work at 30 V common-mode voltage. But what can you say about the level-shift circuit?
Zeners has low differential resistance and will not cause attenuation. You can use any 3 pin voltage regulator as a current source. But I have no idea if it will work in reality. What can you say about this?