Other Parts Discussed in Thread: LDC1000EVM, , LDC1101EVM, LDC1101, LDC1614
I am trying to use the LDCCOILEVM coil B or C (same coil) with the LDC1000EVM to sense the position of a target as it moves linearly across the coil. We have tried a few different capacitors to achieve differing results. We have used a 33 pF capacitor (which according to other posts is smaller than suggested) to achieve a frequency around 5 MHz and a 820 pF capacitor to achieve a frequency around 1 MHz. The 5 MHz frequency sensor is to sensitive for our application due to the high frequency, but looking at the coil datasheets it gives us a very high quality factor in comparison to a 1 MHz frequency.
Looking at our resulting data with the 5 MHz sensor with Rp_min = 54 and Rp_max = 21 we get our largest range of data from ~1000 to ~18000. Toward the lower end of that data the noise will range about 100 data points and toward the top the data will range about 500 data points. Also due to the high frequency, touching our target will cause the signal to jump 1000 points on the lower end and 6000 on the higher end.
Looking at our resulting data with the 1 MHz sensor with Rp_min = 62 and Rp_max = 29 we get our largest range of data from ~850 to ~19850. Toward the lower end of that data the noise will range about 100 data points and toward the top the data will range about 200 data points. Due to the lower frequency, touching our target seems to barely have much affect on the data points.
We are curious as to how the quality factor plays into the sensor design and if it even should be considered as it seems we get better resulting data using a lower quality factor? We also are curious if for a linear application if this amount of signal to noise is considered normal or if the configuration could be tuned to see better quality results? Also as suggested in other threads we have ordered the LDC1101EVM to replace the LDC1000EVM. What are the main differences between these devices as it isn't very clear what they are?
Any help would be appreciated.