Is it safe to use spindle ground for a probe?

[Alijambo73]

My spindle is passing the ground through the bit. Im using a duet 3 6hc and the probe is connected to io6. Is it okay to remove the probe ground and just have a single wire connected to io6.in and use the spindle ground?

I read somewhere to measure the ac and DC voltage between the duet power in ground and the spindle. The ac voltage was 0 and the DC voltage is .03v. Based on what I read with those measurements it should be OK to use the spindle ground and the io6.in.

Should I tie the -24v out to the ac ground?

I would just like confirmation that this will be ok.

Thanks

[dc42]

@Alijambo73 in principle it should be OK to use a single wire provided that -VIN is tied to the AC ground to which the spindle is connected. However, in view of the possibility of things going wrong if ground become disconnected, my preference would be to use an opto isolator between the probe/spindle circuit and io6.in.

[Alijambo73]

@dc42 thanks. I have ordered a octocoupler. In the meantime time I was going to ground the DC to mains. Just to clarify, would I connect the DC out from the power supply or should I connect the VIN- ac ground.

[dc42]

@Alijambo73 your PSU DC out negative terminal should be connected to VIN- on the Duet, so it makes no difference.

[Alijambo73]

@dc42 thats what i thought but i'm never quite sure of my own thoughts. So I will ground the PSU Negative to ac mains and use the octocoupler.

Thanks