Re: [Emc-users] Renishaw TP200 probes

2017-08-11 Thread andy pugh 
On 11 August 2017 at 20:34,   wrote:

> In general, a strain-gauge probe has a strain-gauge
> amplifier followed by an adjustable comparator
> output that says when strain (from contact) is
> "absent" or "present".

I know lots about strain gauges, I have used them extensively in previous jobs.
The fun thing here is that the probe head has only two contacts (a
screw with a gold-plated cone in the middle).
I am starting to wonder if it is working on a protocol like one-wire.
The head contains LEDs, and I don't know what else. There is automatic
nulling but that might be in the interface unit.

> What is really needed to fix that is gold-plated
> (maybe gold over nickel over copper?) balls and
> bars, but it's hard for DIYers to do that,

Have you considered tungsten carbide? (yes, it does conduct)


> Let's talk more about strain gauge probe design after
> you get to know your TP200 a little better.

Well, so far I have concluded that it is the thing least likely to
come apart easily that I have considered taking apart

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Renishaw TP200 probes

2017-08-11 Thread kim 
Hi Andy, 

In general, a strain-gauge probe has a strain-gauge 
amplifier followed by an adjustable comparator 
output that says when strain (from contact) is 
"absent" or "present". The probe never really 
deflects in the usual 6-ball/3-bar way, it is 
mounted solid (hence their really nice magnetic 
breakaway attachment to minimize crash damage.) 

I don't know the details of how the TP200 
strain-gauge probes work, but I would like to, 
as I have been considering making a strain-gauge 
probe from scratch to get rid of the 6-ball/3-bar 
poor-contact problem. 

What is really needed to fix that is gold-plated 
(maybe gold over nickel over copper?) balls and 
bars, but it's hard for DIYers to do that, so 
I've been thinking strain gauge, since that 
trades for a new set of problems that are 
hopefully easier to solve. 

Anyway, your probe uses Renishaw's PI 200 interface 
(apparently the PI 200-3 was the latest version they 
produced). Info (legacy) on the TP 200 and PI 200 here: 

www.renishaw.com/media/pdf/en/cac977125ed24a8281fdfaea0497d2da.pdf

www.renishaw.com/media/pdf/en/6d3e76d96a744ca4b576d8793c29dab8.pdf

www.renishaw.com/media/pdf/en/4060f184857d437d930d498c266d6cef.pdf

I am also looking for legacy probe info. I would like 
to know details of the IR optical signal produced by 
a TP7-TP8-TP9 (& TP10?) touch probe. The receivers are 
the MI 4, MI 7, MI 12 interfaces (I have the MI 4, but 
no probe). Or perhaps to borrow a probe to observe 
the signals it puts out. (I should have started a new 
thread, but I imagine this IR stuff will go nowhere.)

Let's talk more about strain gauge probe design after 
you get to know your TP200 a little better. 

Kim


 Original Message 
Subject: [Emc-users] Renishaw TP200 probes
From: andy pugh 
Date: Fri, August 11, 2017 12:35 pm
To: "Enhanced Machine Controller (EMC)"


Does anyone know how the Renishaw TP200 probes work? I bought one from
eBay by accident.
I thought that it was a SP20, which is a conventional 6-ball/3bar
probe, but the TP200 is a strain-guage probe.

5V on the connector makes the LED glow. prodding the stylus seat has
no effect on the LED or the current flow. It was listed as "not
working" so perhaps it is completely broken. Possibly a cracked strain
gauge, for example.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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