# Which Magnetic Scales



## Hozzie (May 11, 2021)

After reading one of the other threads I have decided I like the idea of using the TouchDRO system.  I plan to order Magnetic scales to put on my Jet JTM-4VS.  It has an old Sargon DRO which works, but is only 2 axis.  I decided to just go ahead and replace everything with new now, add a Z and tach and be done with it.

So looking at Magnetic scales, I am basically going by some common brands.  There is Ditron at the cheaper end, but they seem to work pretty well from what I can tell and then I have looked at the Mitutoyo's which are more expensive.  I am not against spending the money if it makes sense, but I am not sure if it is really needed.  I am just a home hobbyist.

So what I have looked at:

Mitutoyo: https://www.mscdirect.com/product/details/05936141 
What I can't seem to find is the voltage, etc these use so not sure they would even work.  These appear to be ABS scales so not sure that is supported either.   To get all three sizes I am looking at approx $900.  Maybe there are other version of the Mitutoyo's I should be looking at if I want "better quality" scales than the Ditrons?

Ditron:
I see they show three different types (DMA, DMS, DMB).  No idea what the differences are and which may be the best option.  I am guessing these would be around $500.  I am confident these are supported.

Are there better options?  Recommendations?

While I am asking I figure Yuriy will see this.  I was looking at getting the Lenovo Tab M10 Plus, 10.3" FHD Android Tablet, Octa-Core Processor, 64GB Storage, 4GB RAM tablet for the display.  Is 4GB RAM good enough?

Thanks.


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## JimDawson (May 11, 2021)

I have Ditron DMR-200 1 micron read heads on my lathe.  About $100/ read head and about $30/meter for the magnetic tape.  I can't see any difference between those and Renishaw units that I have on my mill.


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## ycroosh (May 11, 2021)

I don't have any experience with Mitutoyo magnetic scales, so I can't comment on those.
On the other hand, I know a fair number of people who use Ditron DMR-200 and DMR-500 scales and they seem to be very good. I have DMR-500 on my mill (on the X-axis), and for a long time had one on the lathe's Z axis and haven't had any problems. If you get a version with bulk tape, the edges tend to collect fine swarf, but the ones that have the tape in the aluminum extrusion with a stainless steel cover don't have this problem. Other than that, they have been very accurate and trouble-free for several years now.
One caveat I have is that these scales are very particular about the input stage, so I strongly recommend the new version of the pre-assembled TouchDRO adapter. If you absolutely insist on a scratch-built adapter, use pull-up resistors with at least 47KOhm resistance and some sort of buffer (i.e. a simple resistor divider will not work very well).

Hope this helps
Yuriy


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## Hozzie (May 11, 2021)

Thanks, I wasn't considering anything other than the versions with the tape in the aluminum extrusions and covers so that shouldn't be an issue.


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## cathead (May 12, 2021)

I'm using a Mitutoyo 2 axis KA counter with magnetic scales on my vertical mill and have to say that I have been very
happy with it.  Having used it for some years now, it's operation has been flawless.


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## ycroosh (May 12, 2021)

cathead said:


> I'm using a Mitutoyo 2 axis KA counter with magnetic scales on my vertical mill and have to say that I have been very
> happy with it.  Having used it for some years now, it's operation has been flawless.


Do you use them with TouchDRO, or their own display?


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## Hozzie (May 12, 2021)

I ordered 3 Ditron 1um scales sized for my exact needs.   $509 total delivered.  Ditron was easy to work with and swapped out the 5um scales for the 1um for no extra cost.  I also ordered the V2 adapter and case so that should be good.  I got some good feedback in PM about considerations, but being in the software business, I like the idea of this concept.  I am an Apple guy, but will get an Android tablet ordered.  Should be fun to setup.


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## frostheave (May 12, 2021)

JimDawson said:


> I have Ditron DMR-200 1 micron read heads on my lathe.  About $100/ read head and about $30/meter for the magnetic tape.  I can't see any difference between those and Renishaw units that I have on my mill.


Jim,

Did you have a source for the aluminum rail and stainless tape cover?  Or, did you use another mounting method?

Thanks,
Bob


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## Hozzie (May 12, 2021)

frostheave said:


> Jim,
> 
> Did you have a source for the aluminum rail and stainless tape cover?  Or, did you use another mounting method?
> 
> ...



The one's I ordered are in the rail with the cover.  If you did three axis at his cost, you are at ~ $360.  Then you have to buy the rail and covers.  Not sure it would be worth the effort to do vs. just buying them in the rails already at the exact lengths you need.

If it helps anyone, these are the items I ordered.  You will need to message them for the specific lengths you want and then they will have you purchase based on the 5UM and they will update the order.

DMA2-950MM (The dro can read  950mm .  Total length of magnetic scale  =1069mm )
DMA2-350MM (The dro can read  350mm .  Total length of magnetic scale  =469mm )
DMA2-450MM (The dro can read  450mm .  Total length of magnetic scale  =569mm )

They said the DMA2 represents the 1um scales.  

This is the link to the page for the actual product.








						125.12US $ 8% OFF|High Precision Rs422 Ip67 Magnetic Scale 5um 50-500mm Reading Length Magnetic Linear Encoder Mainly Used For Woodworker - Level Measuring Instruments - AliExpress
					

Smarter Shopping, Better Living!  Aliexpress.com




					www.aliexpress.com


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## frostheave (May 12, 2021)

Hozzie said:


> The one's I ordered are in the rail with the cover.  If you did three axis at his cost, you are at ~ $360.  Then you have to buy the rail and covers.  Not sure it would be worth the effort to do vs. just buying them in the rails already at the exact lengths you need.
> 
> If it helps anyone, these are the items I ordered.  You will need to message them for the specific lengths you want and then they will have you purchase based on the 5UM and they will update the order.
> 
> ...


Very good.  Thanks for the info Hozzie.


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## cathead (May 12, 2021)

ycroosh said:


> Do you use them with TouchDRO, or their own display?


I am using the Mitutoyo KA counter display.


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## ycroosh (May 12, 2021)

cathead said:


> I am using the Mitutoyo KA counter display.


Ah, darn. I was hoping someone figured out how to make them work with TouchDRO.
I'm sure they work spectacularly well with the Mitutoyo display


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## JimDawson (May 12, 2021)

frostheave said:


> Jim,
> 
> Did you have a source for the aluminum rail and stainless tape cover?  Or, did you use another mounting method?
> 
> ...



I ordered the tape directly from Ditron
sales@dcoee.com
http://www.dcoee.com/


DMR200 1um Read Heads
MS200-2M 2+2  (2 meters tape)

I don't use the aluminum rail, just direct mount on a flat surface.

Z axis Knee






X axis





Y  axis





Quill Z


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## frostheave (May 12, 2021)

JimDawson said:


> I ordered the tape directly from Ditron
> sales@dcoee.com
> http://www.dcoee.com/
> 
> ...


Wow, it's amazing that they stay accurate with all the chips!
Thanks for the pics and the info.  I just might have to give it a try.

I'm guessing the magnetic tape has adhesive on it?

Bob


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## JimDawson (May 12, 2021)

frostheave said:


> I'm guessing the magnetic tape has adhesive on it?



Yes, 3M it ain't never gonna come loose tape.  Pretty much impervious to coolants and petroleum products.  I replace my X tape after about 6 years.  I spilled some acetone near the end of it and it started coming loose after a while.


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## ycroosh (May 12, 2021)

Bob, I would add wipers, though. Swarf that gets in between the tape and head does actually affect the reading. Ditron seems to be using decent interpolation hardware, but I was able to detect some jitter on a dirty scale that disappeared when I wiped the scale down. My scales came with rubber wipers, but I replaced them with some hard felt and it seems to be holding up for about three years.
Yuriy


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## frostheave (May 13, 2021)

That's a good idea and cheap easy insurance.  I'll do it.
Thanks Yuriy.
Bob


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## Hozzie (May 20, 2021)

So I got my magnetic scales today, but I haven't unpacked them yet.  Come to find out the old DRO head on my machine was old, but as I was taking off the old scales, I noticed that they are Accurite glass scales (SENC150 and SENC125).  Both 5um scales.  I decided to clean the X up and figured before I try to reinvent the wheel, I would give them a try.  As a side benefit, if they work, I can use the magnetic scales when my PM1440GT gets here and save the DRO cost for that.  The old DRO worked so I would think the scales themselves are still ok.

The wiring diagram for them has an A+, A-, B+, B-, 0, +5, R+, R-.  So I ignored the R's, but did hook up the A- and B- to the A' and B' on the board (as well as the other obvious ones).  The board started up ok and I was able to connect to it, but I wasn't getting any readings.  Should I disconnect the A- and B-?  Not sure if that is causing an issue.


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## ycroosh (May 20, 2021)

Hozzie said:


> So I got my magnetic scales today, but I haven't unpacked them yet.  Come to find out the old DRO head on my machine was old, but as I was taking off the old scales, I noticed that they are Accurite glass scales (SENC150 and SENC125).  Both 5um scales.  I decided to clean the X up and figured before I try to reinvent the wheel, I would give them a try.  As a side benefit, if they work, I can use the magnetic scales when my PM1440GT gets here and save the DRO cost for that.  The old DRO worked so I would think the scales themselves are still ok.
> 
> The wiring diagram for them has an A+, A-, B+, B-, 0, +5, R+, R-.  So I ignored the R's, but did hook up the A- and B- to the A' and B' on the board (as well as the other obvious ones).  The board started up ok and I was able to connect to it, but I wasn't getting any readings.  Should I disconnect the A- and B-?  Not sure if that is causing an issue.


I would start with +5V, Gnd, A and B. The scales should be compatible (quick Google search suggested that they are TTL), so it's probably a connection issue.


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## Hozzie (May 20, 2021)

Well, no luck.  I tried just using the 5v, 0, A, B, but it didn't seem to do anything either.   I had already wired one scale (z) for the new magnetic scale as I still wanted to add it regardless so I tried it as well.  No luck with it either.  

Some details which may help troubleshoot.  The mill is not connected to anything.  It's just sitting in the middle of my shop so there should be no electrical interference.  I did try a USB power supply as well as a wall power supply.  With the USB I was showing 5.05 volts at the pins coming out of the TouchDRO board.  With the tablet charger I was showing around 4.7. 

I did notice there is a small LED on the new magnetic scales which I believe should light up with power.  It does not.  Maybe there is some ground issue I am not finding? 

I tried to hold the magnetic head near the magnetic scale just to see if there was some type of resistance required, but that didn't seem to do anything either.  

Anything else obvious to try?


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## ycroosh (May 20, 2021)

The LED on the scales that I have light up when the scale is aligned correctly and is off otherwise (when the scale is powered up). 
Just to make sure, can you confirm the following:
1. The board is powering up (green LED on, blue LED blinking)
2. You can connect to it via the tablet (TouchDRO shows up in the list of devices and the app can connect and stay connected)
3. When you move the scales, the display in the app is not changing
4. This happens on all 4 inputs (W needs to be enabled in the settings to be displayed or added to another reading)
5. Voltage between the Vcc pin and Ground pin is around 5V (+/- a few % is not a big deal) when all scales are disconnected
6. Voltage stays the same when a scale is connected (all four lines are wired in parallel, so you can plug in X and measure Y, for example)
7. Voltage between A, B, A' and B' is around 1.75V +/- 0.1V when no scales are connected
8. When a scale is connected, you see voltage close to 0V or 5V (depends on the current position, should change when the scale is moved)


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## Hozzie (May 20, 2021)

I think I figured out the issue, although I will need new pins etc to verify.  Just a stupid mistake on my part.   I am pretty sure what has happened is that I was using the number of the pin sockets in reverse thinking I should be looking at it from where it plugs in from the scale and not from the back of the connector.  I think I connected what should have pin 1 to pin 5, etc.

The real problem is now all of my cables and connectors are useless.  Yuriy, I will pm you and pay you to send me some new connectors and pins.


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## JimDawson (May 20, 2021)

Sounds like the read head is not getting power.  The LED on the head should come on when powered up, red when not near the mag strip, and green when it is in the operating range, about 0.020'' or so.

Best guess is a wiring issue.


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## Hozzie (May 20, 2021)

JimDawson said:


> Sounds like the read head is not getting power.  The LED on the head should come on when powered up, red when not near the mag strip, and green when it is in the operating range, about 0.020'' or so.
> 
> Best guess is a wiring issue.


Yeah, I have no doubt it is a wiring issue due to my reversing the pin orders inadvertently.


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## Hozzie (May 23, 2021)

Rewired one of the connections this morning after getting some new wires and such from Amazon.  All is well with the world as the old X glass scale seems to work just fine.  I will wire up the others and should be good to go.  Glad it was my fault and not something more difficult to figure out.


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## WEL0058 (Nov 22, 2021)

FYI - If you are talking about removing DB9 pins from the connector, there is a simple tool which is used to extract the pins out.  







YouTube Demonstration  https://www.youtube.com/watch?v=XEYXlgnSyhA

Nice thing about all these electrical connectors the able to change pin outs and reusability.


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