I had an idea about using velostat for making a 3d touch probe and finally tried it out today and it works in principal! It is simple to construct and costs less than $5 in parts. It is essentially a variable resistance sensor. The velostat's resistance is reduced when it is compressed. It works much the same way a strain gauge works but with a much larger response which can be measured on a 12bit ADC. The measurement is relative as absolute values are dependent on temperature and other factors. Signal to noise is ~< 0.5% and it can be configured to trigger at different relative pressures.


I had a few questions:

what is the best way to test it's accuracy?
How are 3d touch probes typically tested and calibrated?
How much pressure is typically put on a probe (Renishaw ball type) before it triggers? Does it just depend on the size of spring used?


My idea to test it is to put it on my manual mill and compare triggered values with the DRO values. This would require me feeding it until a led illuminates and this may not be the most repeatable test...

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