ADS8588SEVM-PDK: Simultaneous Sampling of Two Analog Triaxial Accelerometers

Hello Larry,

Looks like ADXL326's ouput is a single-ended signal between 0.1~2.8V, however it shows a small output range between -29mV to 190mV for self-test mode, can you please confirm if you need to sample this small signal for test mode or confirm the signal range you want to convert?

ADS8588S can only support +/-5V or +/-10V input range, hence it's not a good option for you without external amplifiers since you will lose dynamic range.

ADS128S102 is not simultaneous-sampling ADC.

We are looking at ADS131M08 which may be the best ADC with internal PGA for your application if you can confirm the range of your output signal to the ADC. I have talked to my co-worker, Joe, who is an expert to support this ADC. He will check and support you after you confirm.

Thanks.

Regards,

Dale

Larry,

The ADS131M08 does look close to what you want. However, I would be concerned with the output range of the voltages coming out of the accelerometer board. I would note that the ADS131M08EVM is limited to a reference voltage of 1.3V, which then limits the analog input range of the ADC to a differential ±1.3V. As Dale mentioned, the ADS131M08 does have some gain built into the device, which makes it easier to measure smaller signals. However, it won't measure larger signals without some attenuation.

Another possibility would be to use the ADS1278EVM or ADS131E08EVM, which have larger input ranges. However, these EVMs were developed many years ago and may have problems with newer versions of Windows (8 or 10).

Joseph Wu

Hi,

Thanks for the input. My application will likely only require up to about 3 or 4 g, so the ADXL326 might not be the best choice. I could switch to the ADXL335 to utilize the full range.

I just realized that the Adafruit accelerometer board uses 0.1uF for the XYZ filter capacitors to set a 50 Hz bandwidth – that seems like it would be a problem.

FYI, I was originally using the MSP-EXP430FR5994 development kit, which could power the accelerometers at 3.3 V and monitor all six channels, just not simultaneously.

Larry

Hi Larry,

If you need further support or suggestion, please let us know and confirm more information including ADC's channels, your signal range etc. If a simultaneous sampling is not required and your signal is also not high up to +/-10V or +/-5V, ADS8588S is not a suitable ADC for you.

Regards,

Dale

Hi Dale,

As I mentioned, my application will require measuring accelerations up to about 3 or 4 g so it probably makes sense to switch accelerometers to something with a lower range. I do require simultaneous sampling. I only mentioned using the MSP-EXP430FR5994 development kit to point out that it does not provide simultaneous sampling, and switching consecutively between six channels is much too slow. My application requires all six acceleration signals to be measured simultaneously so that I can do real time calculations for positional information. If there is any delay in reading the individual signals then the object will have moved and the position calculations will be inaccurate.

I need help selecting the best EVM that will power the two accelerometers and allow me to read them simultaneously, then do calculations based on the 6 acceleration values. Eventually I need to couple this to a wireless system to transmit the results of the calculation to another module, but right now I am focusing on just the simultaneous sampling problem.

Thanks,

Larry

Hi Larry,

As Joe and I mentioned, we do have some ADCs including ADS8588S, ADS131M08, ADS1278 which may be good for your application, however both Joe and myself tried to check with you about the output range of the voltages coming out of the accelerometers, we do not know the signal range of 3 or 4 g you mentioned, so we need your clarification to recommend a best ADC for you.

Thanks&Regards,

Dale

Hi Dale,

 The signal range depends on the acceleration range of the accelerometer and the voltage used to power it. I am currently using a +/- 16 g accelerometer. If I power it with 3.3 V then +/- 4 g would range from 1.2375V to 2.0625 V. If I power it with 5 V then it would range from 1.875 V to 3.125 V. However, I’m thinking I should switch to a +/- 4 g accelerometer for better resolution. If I power that with 5 V then I will need to be able to measure the full 5 V.

 Larry

Hi Larry,

ADS8588S can be used for your application, however you will lose dynamic range without external signal conditioning circuit because this ADC only supports +/-5V or +/-10V input range. 

ADS131M08 is a better option for you in terms of input signal and  simultaneous sampling requirement, please check ADS131M08 datasheet and EVM User Guide.

Regards,

Dale