DRO is driving me crazy.

[Neil WyattModerator @neilwyatt]

Or, as the units are low voltage, try 'lifting' the earth in one of the cables.

Neil

[John Stevenson 1Participant @johnstevenson1]

Screened cables should only be earthed at one end only. Earthing both ends causes an earth loop

[Rik ShawParticipant @rikshaw]

Thanks John, several others have said much the same so I intend checking out cables tomorrow.

Christopher – the speed trick makes no difference, the display still gets corrupted.

One more thing, I have tried with just the one lead connected at a time – the problem is still there.

Finally (for this post at least) because I am not working the machine but rather concentrating more on how the display is changing when cycling the "ON" / "OFF" button I notice that when the display does "loose its marbles", it is changing from 0.00mm to 5.09mm more often than not. I had not noticed this previously. For me the mystery deepens.

Rik

[David Clark 13Participant @davidclark13]

5.09 is as near as dammit 0.2" I think.

[John Stevenson 1Participant @johnstevenson1]

Posted by Rik Shaw on 27/12/2015 16:02:05:

Finally (for this post at least) because I am not working the machine but rather concentrating more on how the display is changing when cycling the "ON" / "OFF" button I notice that when the display does "loose its marbles", it is changing from 0.00mm to 5.09mm more often than not. I had not noticed this previously. For me the mystery deepens.

Rik

I have noticed this on callipers, the value of 5.09 and I'm sure it has something to do with how wide the capacitance bands are on the scale ?

I don't know enough about these things to be sure though.

[Anonymous]

Disconnecting one end of the shielding is not necessarily a cure all. It is good for shielding against capacitive coupling, but does nothing for magnetic coupling. To shield against magnetic fields both ends of the shield need to be connected. It all depends upon the nature of the interference and is often a case of trial and error to see what works.

Andrew

[Les Jones 1Participant @lesjones1]

John is correct about the 0.2" spacing of the bands on the track. All types of Chinese scale use this track spacing no matter what communications protocol they use ( 2 x 24 bit, BIN6, BCD7 and 21 bit.) and it is a known problem that they can be effected by electrical noise which causes the reading to jump in multiples of 0.2". That bit of information would suggest it is the scales themselves that are being effected but it is odd that the reading on the scale itself does not change. Other than the scales that use the 2 x 24 bit protocol the information output by the scales is what is shown on the display. The 2 x 24 bit scales output the raw data in one of the 24 bit frames and also the value displayed in the other 24 bit frame. Even if the scales use the 2 x 24 bit protocol I would still expect the value displayed on the scale to change as this is calculated from the raw data.

Les.

[Ian PParticipant @ianp]

Posted by David Clark 1 on 27/12/2015 16:05:33:

5.09 is as near as dammit 0.2" I think.

Not sure what the relevance of that statement is? but 5.09mm is quite a bit different than 5.08mm which is much closer to 0.200" anyway.

That value jump in display reading is related to the 'pitch' of the capacitive scale elements

Ian P

[David Clark 13Participant @davidclark13]

Hi Ian Phillip Track on scale was my thought confirmed by others.

[Rik ShawParticipant @rikshaw]

Update: I needed to do a small job on the mill today using the vice and my new Stephenson's block ( great bit of kit). I did not need to use the DRO but I thought I'd use it anyway as any use at all might help sort the problems I have been – and still am – having with these Chinese scales and independent X Y readout unit.

With work peice secured against stops I zeroed X and Y and moved Y to first co-ordinate. Next I tried to move the X to its co-ordinate but the readout stayed at zero no matter how much I wound the table. What the four and a half is going on now I thought. I suspected the mini B type USB'ish connectors and sockets so I disconnected them and gave a squirt of RS contact cleaner which had no effect at all.

All that was left to check was the stand alone twin axis readout unit. I upside downed it on the bench and removed the battery cover and exposed the two lithium cells. Wearing my super mag specs I could see a couple of tiny smears of liquid on each battery. I removed the batteries and saw further minute traces of moisture on the gold coloured battery contacts.

I dried the moisture with cotton buds and applied a thin smear of lubricating contact cleaner, reassembled and bobs your uncle, all was working properly again. Why had this never occurred before?

Explanation: Yesterday afternoon my normally warm and insulated workshop became uncomfortably warm due to the unseasonably high temperatures so I turned the heating of. When I quit the workshop yesterday afternoon I forgot to turn the heating back on. I only realized this morning when I entered the workshop and felt it distinctly chill at which point the heating went back on.

Some hours later as explained I found the problems caused by condensation.

I fondly imagined that I had experienced all the problems that these budget DRO's can suffer from – how wrong can you be.

Rik

[Brian WoodParticipant @brianwood45127]

The 0.509 mm error on calipers also begins to appear as the battery voltage declines.

Brian

[Brian WoodParticipant @brianwood45127]

The 0.508mm error on calipers begins to appear as the battery voltage declines

Brian

[Michael GilliganParticipant @michaelgilligan61133]

The following [quoted from a previous post] may be of interest.

MichaelG.

…………….

.

For info.

The native resolution of the Sylvac system [which is what the Chinese 'cloned' ] is in imperial measure …

MichaelG.

.

Edit: [copied from my post on a previous thread]

There is some interesting reading here

… especially the comment by Hans U. Meyer

MichaelG.

.

P.S. You can find his Patents on espacenet

Inventor = MEYER HANS ULRICH [CH]

Edited By Michael Gilligan on 13/01/2015 20:38:42

[Ian PParticipant @ianp]

Rik

If the liquid you saw on the battery contacts was condensation then your whole workshop and machines must have been drenched! To me I would think that the liquid was not water but possibly leakage from the cells or maybe some sort of protective grease.

Condensation occurs when humid air comes into contact with surface at a lower temperature than the air containing the water. Since the batteries and the gold contacts are inside the DRO enclosure the temperature of those metal parts will only change slowly, in any event as the humid air has to find its way through small gaps in the DRO enclosure the likelihood of significant condensation is remote. Those metal parts have very low thermal mass and their temperature would track the whole enclosure.

The fact that the DRO worked after you cleaned the contacts might just be happenstance.

Ian P

[JonParticipant @jon]

Posted by Ian Phillips on 26/12/2015 21:41:18: If the DRO setup is a standard Warco option then surely they should have some responsibility to provide reliable operation.

Ian P

Had all listed above symptoms way back in 2000 anyone that wants the 3 axis readout can have the thing.
5 months wait and delivered else where as well.

[Ian PParticipant @ianp]

Posted by Jon on 26/01/2016 21:35:36:

Posted by Ian Phillips on 26/12/2015 21:41:18: If the DRO setup is a standard Warco option then surely they should have some responsibility to provide reliable operation.

Ian P

Had all listed above symptoms way back in 2000 anyone that wants the 3 axis readout can have the thing.
5 months wait and delivered else where as well.

Jon, I'd be interested in having it. I don't mind a challenge and like making things work.

Regards

Ian P

[Rik ShawParticipant @rikshaw]

Ian – "whole workshop and machines must have been drenched" .

This was not the case, the only signs of condensation were as I have described.

Rik

PS Jon – If you have the time / inclination to PM me re: a certain machinery supplier I would be happy to respond.

[Ian PParticipant @ianp]

Rik

I do not doubt your description, also the fact that the DRO is working and the problem resolved is what matters. I'm just at a loss to understand the physics of how water was only found at the battery contacts.

When you started this thread you were experiencing error related to switching the machine on and off, did you ever solve that problem and if so, how?

As it seems to be a not uncommon problem, what you did to fix yours would be useful information to relate here.

Ian P

[Neil WyattModerator @neilwyatt]

Posted by Brian Wood on 26/01/2016 18:20:43:

The 0.508mm error on calipers begins to appear as the battery voltage declines

Brian

At least it's gradually reducing

Neil

[Rik ShawParticipant @rikshaw]

Ian – I am as puzzled as you are as to why I only found water traces on the lithium cells and battery contacts but nowhere else. I really have no explanation. I am just glad I found out what was causing that particular problem.

When I started this thread I reported that it seemed that errors occurred on the DRO heads up readout when cycling the power on and of using the ON/OF buttons on the control box. It is early days yet but I think I may have accidently discovered a way of mitigating the problem. So how?

Some weeks ago the speed control board went bang and I had to order another. After installation of the new board I noticed that with the speed control knob set at its lowest setting a press of the power on button simply illuminated the speed display but the spindle did not rotate. Only after rotating the speed controller a few degrees clockwise did the spindle start. Looking at the documentation for the board I could see that this could be corrected by adjusting one of the miniature pots. But I left it as it was because I had a cunning plan.

Before the big bang the readout used to periodically loose its marbles – as previously explained – when pressing the STOP button. I began to wonder if this button was arcing and causing the read out anomaly problem. What got me thinking though was while chatting to a bod at WARCO, I mentioned the read out problem whilst ordering the new board. He told me that the speed controller should always be returned to zero position before both starting and stopping the mill (and the lathe as well). Mine is not to reason why so I have complied.

Its early days yet and I have not used the mill very much since fitting the new board but I have stuck to WARCO's advice. I have also left that mini pot set as received and so far I am pleased to say I have not had any more read out faults when powering up and down. Fingers crossed then !

But life is never that simple is it? As I said earlier I have not been using the mill a lot since fitting the board and during these periods of non use I have disconnected the mill from the mains but left the DRO switched on and set at zero on the X and Y. Four times in the last couple of weeks the zero has changed to a random reading without me touching anything. If I had any hair I would have torn it out by now

Rik

[Michael GilliganParticipant @michaelgilligan61133]

Rik,

Forgive me if I labour the point, but I think it's worth directly quoting from the link that I re-posted yesterday:

• At 2 March 2012, 10:30:16 user Hans U. Meyer wrote: [reply @ Hans U. Meyer]

• Here's why the Chinese Caliper's binary output is not to scale: I designed it for Sylvac in 1982, when the small number of on-chip transistors limited the options. Hence a scale pitch of 5.08mm=0.2inch, easy to subdivide in both metric and inch with serial binary (LSB first) arithmetic logic. The same logic also calculated the serial BCD output in mm or inch for the display. The serial binary signal, common to both units, was output as an afterthought: only few people wanted it, to which Sylvac simply sold binary-to-BCD-to-RS232 adapters.

  Chinese calipers use very, very similar chips (and that's an understatement). One foundry must have modified it to output BCD instead, I think it's the ones Aldi sold in Germany. The display switch-off feature was added as a gimmick by others, as obviously there is a sucker born every minute (good marketing!).

  The moral of the story: have fun cutting jaws of Chinese calipers and selling homemade DRO kits to the DIY market! As for me, I've been there, done that, and moved on a long time ago. Calipers from Sylvac and other manufacturers (including Chinese ones) are now inductive (insensitive to coolant) and have an RS232 output with galvanic separation. Talking about this, those old directly coupled 1.5 volt interfaces are very sensitive to ESD and ground loops; I wouldn't want them on a machine tool.

  That's all for now.

_____________________

.

This may or may not explain your problems … But it's a very good place to start.

MichaelG.

[Rik ShawParticipant @rikshaw]

"But it's a very good place to start."

Forgive me if I have missed your point – were you trying to make one?

Rik

[Ian PParticipant @ianp]

Posted by Rik Shaw on 27/01/2016 19:39:46:

"But it's a very good place to start."

Forgive me if I have missed your point – were you trying to make one?

Rik

Good question Rik.

If I had Hans Meyer's bank account I would not use DROs based on capacitive scales.

Ian P

[Ian PParticipant @ianp]

I have several DRO setups in my workshop, modified cheap calipers on a tailstock, iGaging scales on a mill, and a glass scale system on the lathe. All of them are 100% stable and all stay switched on continuously (iGaging batteries last up to 2 year). Unheated attached garage workshop (fan heater sometimes). If I had a choice I would prefer Newall or similar kit but so far I have had no real trouble with the cheaper stuff.

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Rik Shaw on 27/01/2016 19:39:46:

"But it's a very good place to start."

Forgive me if I have missed your point – were you trying to make one?

Rik

.

Only that Hans U. Meyer, as the inventor of what we now call 'Chinese Scales', might be making some valid points in his remark: "those old directly coupled 1.5 volt interfaces are very sensitive to ESD and ground loops;"

MichaelG.

Don't mind me … I'll stop interfering in this discussion.

Edited for clarity.

Edited By Michael Gilligan on 27/01/2016 20:55:40

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