Filter selection Help and recommendations needed

[fbp]

I’m designing the AFE for a sensor that gives an output of 2-3Vpp.

My design for the AFE is the sensor output which goes to a 2.5m cable, then to a Centre tapped transformer (used for circuit isolation mainly), then to a unity gain instrumentation amplifier (for good CMRR), then to a band pass filter (my freq of interest is 500kHz) and then a notch filter (for 60Hz noise elimination).

I was just unsure if we can place a notch filter after a band pass filter? Or should the notch filter be placed before a band pass filter

I’m getting a lot of electromagnetic noise due to the 2.5 m cable and the power supply source low frequency noise and 60Hz noise which I’m trying to eliminate by designing the hardware to eliminate all the noise.

Please assist me. And which type of filter for both the band pass and notch filter be the best to use to get sharp cutoffs and accurate noise reduction with a clean signal output?

 

[crutschow]

then to a unity gain instrumentation amplifier (for good CMRR)

That only helps for a differential signal with common-mode noise.
Do you have that?

I was just unsure if we can place a notch filter after a band pass filter? Or should the notch filter be placed before a band pass filter

As long as the signal is not high enough to cause amplifier saturation, the bandpass and notch filter order should make little difference in the filtered signal.
But since the 60Hz noise may be the highest, then putting the notch filter first might be the best.

which type of filter for both the band pass and notch filter be the best to use to get sharp cutoffs and accurate noise reduction with a clean signal output?

"Accurate" and "clean" and "sharp cutoffs" are not defined design parameters that can be used to determine the filters you need.
It depends upon how much noise and the frequency of the noise you have relative to the signal level and what signal to noise level you need to detect your signal.
You need to determine those before you can know what filters are needed.

 

[KlausST]

Hi,

I fully agree with Crutschow. You need to decide the target recommendations first. In numbers with uints.

2.5m cable says nothing. I designed a 2m cable sensor electronics with a signal detection in the picoamperes region.

And we also don´t know where this analog signal goes to.
Maybe via an ADC and to a microcontroller? If so, then it´s way more convenient to do lots of filtering on the digital side.

Klaus