Interfacing with M8 Renishaw Probe

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15 Apr 2022 23:33 #240356 by cakeslob
I am trying to interface with a renishaw probe, TP2 and maybe TP200, with M8 connector. I thought a touch trigger probe would be easier to interface but hooking up to a multimeter(nothing happens), I cannot tell which pin is which. I cannot find any information from official renishaw because there is no need. I also have all the information on the external renishaw driver, but I dont know what it means, or how to wire it to a mesa. I was hoping to get away without using the official renishaw hardware.

This is the M8 connector. I cannot figure out which pin is what. A homie from work gave me the probe because they have no use for it, so I really dont want to wreck it before I get to use it. I am under the impression there is another internal driver inside the actual probe. I know the strain force probes have one, and fairly sure the TP2 has one. I get no reading from my multimeter, so I am very hesitant to hook it up to power without knowing the polarity.
If anyone knows the pin out that would be very helpful, or any tips on how I can non-destructively test to figure it out

 



This is a link to the patent for the Renishaw PI4 interface used for trigger force probes. It has a schematic kinda with a detailed explanation of what and how the interface works.
The problem is I dont know what it means relative to the mesa card. What kind of signal is this? Is this just a fancy differential signal?


patents.google.com/patent/US5272817A/en
patentimages.storage.googleapis.com/f3/1...7528c3/US5272817.pdf

 
 



Here are my other resources/references
forum.linuxcnc.org/38-general-linuxcnc-q...-20-probe-connection
forum.linuxcnc.org/30-cnc-machines/41167...6-renishaw-lp2-probe
bbs.homeshopmachinist.net/forum/general/...ersion-for-home-shop
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15 Apr 2022 23:40 #240357 by andypugh
I have a feeling that what you have there is just the interface module, without the actual probe.

What does the other end look like?

(I think that I am in exactly the same position....)

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16 Apr 2022 00:43 #240360 by cakeslob
yeah, thats the docs/patent for the TP2 compatible interface, the Renishaw PI4. While I could not find the exact probe patent for the TP2, I have found for various other probes like the Mp1 (i think) and (either the tp20 or tp200) with schematics for the internal driver. These docs are relevent to my TP200 probe, but since I only have half a TP200 (the m8 side), I cant really test it easily. The TP200 is also a strainforce probe, which I figured would be more difficult to interface to. I assumed since the TP2 is just a touch trigger probe, it might be easier to work with, but it is not simple a switch, but has a driver also it appears. None of the patents or docs say what the pinout is for the m8 connector, because they are supposed to be connected to another adapter. The schematic appears to have the details only related to the probe signal, and 10,11,13 look like they represent the 2 contacts on the probe

So, my issue is two fold, I dont know how to determine what the m8 connector pinout is, or what kind of input I can connect it to a mesa (specifically 7i76 but help will do)

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16 Apr 2022 02:08 - 16 Apr 2022 02:10 #240367 by sivaraj
TP2 is just a switch .Normally Closed contact.
If you check the TP2 data sheet / catalogue it triggers( or contact opens) with few gram force like 5gram force
usually it should be a TP2-5W (5way )
There is only two contact point from TP2 .
Its a NC contact . One point is usually connected ground body
Contact opens with any force on probe tip
1) Outer M8 thread 2) Middle metal contact.
Use these point to check with multi meter
Patent illustration shows the internal structure like 3 balls
Last edit: 16 Apr 2022 02:10 by sivaraj.
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16 Apr 2022 18:39 #240416 by cakeslob
I do not see what you are describing in the manual
www.renishaw.com/resourcecentre/en/detai...ph6-and-ph6m--112781

It also is almost definitely not a simple NC switch. There are no 2 contact points that give me a repeatable closer circuit.

In diode mode I can sometimes get a closed circuit , but it is not repeatable. the circuit is closed and unstable readings until i trigger the probe. Once the probe is triggered, the circuit becomes open and never returns to closed again. This happens in an unrepeatable manor.

I can get a semi repeatable reading using the mV scale, I get around 1mV to .1mV reading, but triggering the probe never closes this circuit, it only changes it (sometimes) by .1mV


I cannot find any info on internal driver for touch trigger probe, but I have found what appears to be internal driver from strain force gauge probes, and some other information on the renishaw input driver, but still not sure how you would replace the renishaw driver with just a mesa driver board

patents.google.com/patent/US5669151A/en
patents.google.com/patent/US4443946A/en

these ones are for the strain force gauge probe

patents.google.com/patent/US4769919A/en
patents.google.com/patent/EP0388993A1/en
patents.google.com/patent/EP0242710B1/en

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17 Apr 2022 11:37 #240457 by Muzzer
I can't claim to be an expert in the matter but I have both an MP1s touch probe and TS27R tool setter, which both use the same "tri lobe" contact concept. While they are normally closed contacts on the face of it, the contact resistance actually changes in a reasonably linear fashion as the probe force is applied. So some of the techniques referred to may well be how Renishaw have extended the precision and repeatability of their probe concept beyond the simple open/closed mode. However, one upshot is that you should ensure that the switch current and detection threshold are around the level used by the special (expensive!) Renishaw interface.

For my machines, I operate them as simple NC switches connected directly to an NC (resistive pull up) digital input and their precision far exceeds what the machines are capable of. IIRC, they claim a potential accuracy of around 1um(?) but I'd be very pleased to achieve an order of magnitude worse than that.

If yours doesn't seem to behave itself when tested with a DVM or an NC input, I'd suspect something isn't right inside. My TS27R was open circuit but simply needed a new cable which I was able to fit once I'd figured out how to dismantle it. These things have been manufactured using conventional means, so they can also be dismantled with care. 
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17 Apr 2022 12:37 #240465 by dm17ry
it is a NC switch. i have disassembled a TP6 probe which is very similar to TP2. inside is a usual kinematic mount with 6 balls shorted by 3 radial pins, nothing more. when seated and measured with a multimeter - the resistance is varied around a few hundred ohms to a few kohms. nevertheless, the renishaw PI4 probe interface unit i also have seems to reliably detect the contact. the interface supplies 12V to the probe (open circuit) and limits the current to 500uA. i'm sure it's not hard to replicate using a comparator IC as shown in patents above
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17 Apr 2022 15:08 #240474 by Muzzer
Indeed. Or like me, just wire it directly to your Mesa etc board like any other NC switch..
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17 Apr 2022 23:51 #240523 by cakeslob
Thank you all for your patience, this was a productive weekend for me. You were correct that it was just an NC switch, and like muzzer suggested, it was something not right with my unit. I think the trigger force was the issue, it appears to have been almost completely out. Once I increased the force by a lot, the meter started behaving as it should.

Now, how might one tackle a strain gauge probe? like the TP200

patents.google.com/patent/US5323540A/en
patents.google.com/patent/US5505005A/en

 
 
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14 May 2022 22:19 #242983 by cakeslob
Just an update, I finished making my M8 probe mount for the TP2, and it was the same issue again where I have an open circuit and probe does nothing. After screwing around a bunch it started to work, but only for 1 trigger and then it would not close again. I looked it, and it appears to be a thing with the TP2 that the other cmm guys know about. They suggested lightly tapping the TP2, and after that it started to work, but quickly did the same thing again.

I was wondering is maybe spraying it with contact cleaner or something, what do you guys think of that? Has anyone else had the same issue before?

www.pcdmisforum.com/forum/pc-dmis-enterp...?p=157659#post157659

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