Cheap Idea for a DRO

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The PIC will do all the decoding and sampling and filtering and will upload a value on request from the display processor. It is fronted by a dual comparator to do the level shift and generates a PWM output to drive the -1.5v charge pump. The output will be in native format (note that the reader always outputs in imperial, metric conversion is done by the display processor)


No, not looked but doubt you will find one...


The 'machined bar' is a PCB, under the graduated label... see here for more info. This makes it hard to extend, but easy to cut down...

Thanks for that Irvine,

Thats interesting. Re the reader units. Am I correct in thinking that the 4 bit BCD type readers do change the transmitted values when switching between metric and imperial? If that is the case it would be a lot easier to get the reader to do the conversion rather than the top end.

Thank's for the insight into the capacitive sensor operation. I was not aware the bar has a strip pc under the label. That's a bit of a nuisance as my plan was to buy cheap 6" calipers and fit longer bars. making long strip pcb's is not out of the question but I guess that the whole reader accuracy relies on the pitch accuracy if the T and comb? Do you know if the comb fingers are isolated from each other or linked together, its hard to see on the photo. It looks like the Ts are isolated from each other.