TIDA-01471: TIDA-01471

Hello FarmerJo,

To operate the board you need a SPI master that can generate data with falling or rising edges of the SCLK, to be able to program the DAC, Shift Register, and the XTR device as described in the user guide page 14 to page16. to grab the data at data rate of 64kSPS you need SCLK running at 2 MHz at least.

In case you don't have the flexible SPI master to operate 3 devices (ADC,DAC, shift register), you can simply override the shift register using J2, J3 as described in page 21 of the user guide, disconnect the XTR current source using J4, and provide external current directly to the sensor. that leaves the need still for a simple SPI running with SCLK of 2 MHz at least.

To get a meaningful dataset for evaluating the design, the SPI master needs to store the captured data over specified time. e.g. 16k points to be able to generate FFT of the input signal. you can examine the time domain data although it wouldn't tell much about the design performance.

I just wanted to clarify the above points before coming to your question about an IEPE sensor.

In fact the performance evaluation doesn't need any sensor, it's recommended to use a high quality signal generator to be able to check resolution, noise, and linearity performance of the design. this is done while XTR current source is disconnected as described above.

Once you are sure the board is properly assembled, properly powered, control signals are properly set, SPI communication with the ADC is running and you get reasonable results in time or frequency domain (by seeing stable 0 for shorted input, or clean sinusoidal matching the input), and your data handling flow is clean so that you could (from time or frequency domain) determine the frequency and amplitude of the input you are ready to go to the next step of testing by attaching a real IEPE sensor.

any standard IEPE sensor from known manufacturers should work fine if the sensor output range is below +/-10V, you can check vendor websites like PCB(IMI), IFM, MMF, TE, DJB for a broad range of compatible sensors.

testing with a real IEPE sensor is a bit tricky though, here are some points to consider:

- I don't think shaking the sensor with hand will give any meaningful data from the acceleration and frequency standpoint. you should attach the sensor properly to a vibrating object with a vibration of cyclic nature like Motor, so that you get a stable tones after FFT. if you want to evaluate your solution though you need a higher end setup where the sensor is attached to a calibrated vibration table which you can control the acceleration level and frequency precisely.

- Testing transients (by applying low level impulses of force to the sensor) is even harder as you need to synchronize the start of the data capture (some filter delay to be taken into account) with the transient even. that would eliminate the possibility that you can abruptly moving the sensor by hand and capturing that using your SPI master.

- majority of the available IEPE sensors in the market have noise floor much higher that the TIDA-01471 circuit, i.e. their performance is much worse and you can't use them to check noise floor of the board anyway if attached to it.