Mitutoyo Acu-Rite DRO Zero Setting

[jpanhalt]

How is zero reset in Mitutoyo Acu-Rite DRO's?  A contact there implied that simply toggling the supply will reset zero, but I am not sure all the linear scales do that in practice.  I am most concerned with the scales used for its inductive DRO's for mills and lathes. In other words, is it done by toggling the supply, toggling another pin, or arithmetically in the readout?

[thm_w]

You have it all setup, wouldn't it be easy to test? According to your document some have an input which let you feed in a value, but yours sounds like output only.
When I did it, it was done arithmetically, was just easier to solve it that way instead of adding additional hardware externally. You'll need to do that if you want an incremental position option anyway.

zero_offset = read_current_position()
...
position = read_current_position() - zero_offset

https://www.eevblog.com/forum/mechanical-engineering/mitutoyo-982-537-1-dro-display-with-series-572-linear-scales/
https://www.eevblog.com/forum/mechanical-engineering/mitutoyo-digimatic-interface-pinout-handbuch/
https://www.eevblog.com/forum/testgear/which-digital-caliper-can-be-interfaced-with-microcontroller/

[jpanhalt]

Yes, before I had to suspend the project last Fall, I had set up an arithmetic calculation.  You are right.  I have not scoped the pins, but I have used a voltmeter on them and haven't seen either a signal or an interruption in VCC.  When I pick up the project again in late September, I will definitely put a scope on the pins. I was just wondering whether anyone had already done that legwork.

[jpanhalt]

Update (edited)

I finally decided to determine how long the 1.5V sensor supply must be toggled to reset the DRO scales to zero. 

My reader is described here:
https://www.eevblog.com/forum/mechanical-engineering/mitutoyo-982-537-1-dro-display-with-series-572-linear-scales/msg5171796/#msg5171796

I used a CD4066 NO analog switch at 5V VDD to toggle the 1.5V going to the scale* and a Rigol DG1032Z ro produce a zero pulse of various widths with a period of 10 s  (i.e.,  high was set to 9.998 seconds for a 2-ms pulse).  The on state was about 5V as well.  It is important to have the 1.5V on for several seconds or the scale freezes up.

With a 1-ms pulse, zero would reset occasionally.  A 2-ms pulse consistently reset to zero.  Shorter pulses did not work. 

EDIT:  I was concerned that the circuit used in the experiments above didn't pull the 1.5V to ground.   I got a pair of SPST NC and NO analog switches (TS12A4515 and TS12A4514, respectively) and wired them as a SPDT as shown in the attachment.**  Transitions were much cleaner all the way to a 100-us pulse and reached ground.  A pulse of 200us caused repeatable reset; 100us didn't.

John

*I initially tried to use the enable function of the MIC2951-adj voltage regulator.  I could not get short pulses with that because of the relatively large output capacitor used.  A pull-down load resistor was tired briefly, but was abandoned.  I didn't have an NC switch, which would have made setting up the pulse generator a little simpler.

**The symbol for each switch has the correct pin label for com, but the diagram of the switch is opposite what I have usually seen.  I was too lazy to change it.  The switches are not directional.