The ADXL335 you are using has a 32k ohms output impedance. Analog Devices specifically did this to make adding a low pass filter simple, just add an external cap across the output and ground. Table 4 on page 11 of the ADXL335 data sheet lists what value caps to put across the output to get the desired low pass filter. This high impedance output means it is unable to directly drive a cable. I have used the ADXL356 in an industrial application and you must add a buffer op-amp located near the ADXL355 in order to drive any kind of load.

If you are driving a cable, this buffer amp needs to be able to handle higher capacitance (most op-amps can't drive more than a couple of hundred picofarads which is a really short cable. Analog devices and TI both have app notes on driving capacitive loads and both sell op-amps optimized for this purpose. At a minimum you should at least add a 100 ohm resistor in series with the output to prevent op-amp oscillation. Check for this oscillation with a scope looking in the MHz range.

https://www.ti.com/lit/an/snoa424c/snoa424c.pdf
https://www.analog.com/en/analog-dialogue/articles/ask-the-applications-engineer-25.html

The output already reaches 3V max so technically you could just connect the output directly to your ADC input (assuming it is on the same PCB. Even so, I would still add a buffer amp that is able to drive your ADC input (delta-sigma ADCs are capacitive loads). There are ADC driver op-amps designed for this specific purpose.

Also what frequency bandwidth do you need for your application? These MEMS accelerometers have an unpleasant mechanical issue that Analog Devices tries their best to hide. If the IC is exposed to high levels of vibration above 2 kHz they will experience DC rectification of noise which in extreme cases makes the output completely unusable. This DC noise rectification issue is reduced by selecting a higher range accelerometer instead (the ADXL335 is only +/-3g range, so you may want to pick a higher range or multiple range sensor instead). I had to switch an oil well pump controller design from an ADXL355 to an ADXL357 because of this. If higher frequency vibration is not present in your application you can ignore this issue.

My background is in signal processing circuitry design for load cells. My experience is the key to low noise is to use low impedance, differential signals with twisted pair wiring as much as possible. DC precision is super important to me, so I also tend to use zero, 1/F noise op-amps as well. A cap across the ADXL335 output signal followed by unity gain voltage follower op-amp plus a 100 ohm resistor in series with the buffer amp output may be all the circuitry you need.

On power supply noise issues, be aware that older 3 linear regulators (like 7805 or LM317) ripple rejection is poor. If you are using a switching AC to DC power supply you will want to follow it with an LDO regulator that has extended frequency PSRR specs to filter out switching noise. I like TI's TPS7A20 for regulating 5VDC down to 3.3V. If your input DC supply voltage is higher, there are family members in the TPS7A family than can handle higher input voltage.

https://www.ti.com/product/TPS7A20

Hello,
Thank you very much for interesting discussion.
I am designing seismic monitor device (bandwidth DC to 100Hz), and using ADXL354 (+-2g) and AD7768. I choose two op-amp difference amplifer, specifically ADA4841-2 (Low 1/F noise). I have a few questions. 1) You mention about "unity gain voltage follower op-amp plus a 100 ohm resistor in series with the buffer amp output", here unity gain voltage follower itself is buffer amp or are you talking about two amp (one is voltage follower, and second is buffer amp). 2) What is your subsequent circuit i.e ADC in said configuration. 3) Where is main point to take care for low noise interfacing high impedance 32kOhms to buffer amp. Thank you

Mod: link to old thread
https://forum.allaboutcircuits.com/...er-for-accelerometer-data.197700/post-1872385

 

I seem to have showed up in the middle of a conversation. Excuse me, folks.