Q: Is there any way to get the read out of axial distance in mm? Or do I need to calibrate it according to my intended use?
There is no way to read out the axial distance in mm, as this is highly dependent on the mechanics.
Parameters are:
- Coil dimensions and design.
- Target material and size
- Temperature
- Oscillation frequency
So any specific system need characterized once and the data used for calculating the distance in a µC.
Q: Can this sensor be used to detect changing lead content in lead acid battery plates during a charge/discharge cycle and thus profile the charge % of such a battery?
To be honest, I never tried this. It could be possible, probably not by measuring the lead plates, but the conductivity of the Acid. Would be worth a try.
Q: I would like to sense if the piston inside an engine block is close to the top or not. the minimum distance between the coil and the piston will be about 15 mm. Is that kind of application possible?
Assuming the engine block is made from metal, it will not work placing the inductor outside. It would need to sit inside.
Q: What would be the max sample rate archiveable (thinking of vibration measurement)
This very much depends on the oscillation frequency and desired resolution. For Rp measurement, it is fosc/Responsetime, where fosc can vary from 5kHz to 5MHz and Responsetime from 192 to 6144.
Q: How can someone communicate with LDC1000 module in order to save data measurments into a file. Is there an api for pc or smartphones?
This is supported by the GUI directly. On the bottom, you can see a “Save To…” and a “Lof Data” button. First specify a file to log to then log data.
Q: Based on the battery question, would it be feasible to do biological, chemical or medical measurements e.g. ion concentration in a liquid (water)?
One test I did was putting some salt corns (2 or 3) into a glass of distilled water. There was a clear difference in Rp result, but only if the coil is in the water. This test was done with the EvKit.
Q: Can You detect large objects, like if a car is on a spot or not? If yes, if You have two different cars, could You determine which one it is on the spot?
There is no physical limit to the size of the coil, as long as requirements for fosc is between 5kHz and 5MHz and Rp is between 1kΩ and 4MΩ. Different cars may give different signatures for Rp and L, but this needs to be characterized.
Q: Is there possible to measure thickness of metal goods? And to what extent?
To some extent. The skin effect also effects the Eddy currents in the target. If the skin depth is more than the thickness of the target, you will read different values for different thicknesses.
Q: What is the maximum distance between sensor and target?
About 70% of the coil diameter as a rule of thumb.
Q: Any recommendation which analog switch to use to multiplex coils (e.g. switching between coils to save system costs)
One possible example for a two channel MUX is the FSUSB42MUX, but almost every differential MUX would do the job.
You mentioned using a multiplexer: when using a muliplexer e.g. to measure two distances in a X-Y configuration we use one LDC1000 hence one excitation signal, apart from the eddy currents needing to die out, how fast can the LDC switch, i.e. how long does it take to get the loop into resonance?
