AccuRemote vs. iGaging DigiMag Digital Scale Comparison

Thursday, July 25, 2013
12" iGaging AccuRemote next to DigiMag scales

Recently iGaging has introduced a new Stainless Steel model of their “Remote Readout” digital scales. The new “AccuRemote Digital Readout” scales are supposedly much more accurate and robust than the older DigiMag model, making them a good candidate for a hobby DRO setup. I’ve been getting emails from people wondering if these scales are compatible with the TouchDRO application (or more accurately, TouchDRO Bluetooth Controller), but since I don’t yet own a set, I wasn’t able to confirm this. When a fellow machinistweb.com forum member CaveBob graciously offered to lend his set for a few days, I jumped at the opportunity. Since Bob gave me permission to take one of the scale apart I think it will be helpful to do a side-by-side comparison to see if the scales are really that much better.

Electronics

DigiMag display works flawlessly with AccuRemote scales

First things first: yes, iGaigng DigiMag and iGaging AccuRemote scales are 100% compatible. They send the data using the same 21 bit synchronous protocol with the same 2560 ticks-per-inch resolutions. Since Bob didn’t include the display units I wasn’t able to check the default clock speed or data acquisition frequency but the old “black” display worked just fine with the scale. Using my test setup I was able to push the acquisition frequency to over 60 Hz using 200 KHz clock speed until the scales started experiencing glitches.Both, the Arduino and Launchpad scale controller read the position just fine.

Both scales use the same part number for the PCB but different revisions

Removing the cover revealed that both scales use the same model of the circuit board, but the revision appears to have changed from 0.05 to 0.06. I wasn’t able to identify any differences, so it could be a slight difference in the embedded chip or something along those lines.

Overall Impression

The differences between the two models is noticeable even at a quick glance. As advertised, the AccuRemote scales use ground stainless steel frames whereas DigiMag’s frames are [extruded] aluminum, anodized on 3 sides. Using my trusty Mitutoyo mike I measured both frames. The stainless steel frame had one spot that was about 0.0002” narrower than the rest while my 35” aluminum scaled had two spots that had over 0.003” gouged out of the side. In practice I don’t think this would matter but the AccuRemote frames are definitely much better made and will probably last longer.

Construction differences are evident even at a quick glance

Reading Head

A much more important difference can be seen between the two reading heads. The older DigiMag scales’ reading head consists of two plastic halves that contain the main circuit board. AccuRemote, on the other hand, use a machined [stainless] steel bottom. The latter fees very solid and slides very smoothly. In contrast the DigiMag scales feel a bit “grainy” and can be wiggled enough to affect the reading by about 1 thousandth.

AccuRemote feel much smoother and robust
thanks to the ground frame and machined slider

Once the cover is take off and the controller board removed the differences become even more apparent. The DigiMag head appears to be supported only by the four flat-head screws. The thin piece of copper appears to serve two functions: a grounding strip and a weak gib pressed against the smooth side of the frame by a small spring. In contrast a much thicker brass gib with two small set screws presses the AccuRemote’s frame against the opposite side of the case, creating very solid setup.

A tiny set screw can be seed in the far corner of the slider

Summary

The differences in construction and build quality between the AccuRemote and DigiMag scales are very noticeable and in my opinion more than justifies the higher price. The new stainless steel frame appear to be ground as opposed to the older extruded aluminum ones. In conjunction with a machine metal reading head body the scales feel smoother and much more solid. If there is indeed a difference in the accuracy between the two models, it would most likely be a result of the improved interface between the reading head and the frame.

At the time of this writing 12” AccuRemote Digital Remote Readout Scale sells for around $60 at Amazon and the 38”-long version is about $50 more. In contrast a 12” DigiMag Scales retail for about half as much, at around $30 and the 35” model can be had for $75 or so.

Quick Update

I’d like to clarify one point that has stirred a small “email storm”: the AccuRemote scales are advertized as “super high accuracy” on some sites, attributing the accuracy and repeatability improvement to the fact that the rule is made of stainless steel. A few readers have made a valid point that SS has lower coefficient of expansion and gave me some flack for not mentioning it. Frankly, I don’t think this is an important factor, and here is why. Aluminum (depending on the alloy) has thermal expension coefficient between 12.8 and 13.2 microinches per Inch-°F whereas stainless steel’s coefficient is around 7.2 (glass is around 5.0). In a context of an average garage this translates to approximately 0.0007” difference in expansion per foot for each 10 °F temperature difference. Assuming that you are dealing with wild temperature swings of 30 °F and are using a 36” scale, the difference in expansion will be around 0.0064” (0.014” vs. 0.0076). Call me crazy, but in a home shop I wouldn't lose sleep over 0.00004% vs. 0.00002% error.

15 comments :

  1. You missed an important point. AccuRemote rules are made from STAINLESS STEEL that expands less than aluminium. That is why the scales are more accurate, not because of the "brass gib".

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  2. Thanks for checking the scales and determining that they are compatible with your DRO project. Just the info I was waiting for before getting these scales.

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  3. Hi
    do you know, if the AccuRemote Digital Readouts are produced by Shane as well ? I couldn't find them on their hompeage.

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    1. I'm not 100% certain, but I'd be surprised if they weren't. The internals look identical...

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  4. i just want to give you my opinion
    the expention is in the problems but not for the reason that you think
    it's simply the fit under the mainrubber of 34" and the sensor mount
    it will take a lot on DigiMag than the ACCUremote
    in cause the expention of the plastic is bigger than the alu or steel
    but for me if you whant to gain precision you just have to rebuilt the sensor mount in aluminium but it's a waist of time for a home shop

    thank's

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  5. Great comparison... it definitely helped by decision to get accuremote scales for my setup.

    Question about your update... You discuss the different thermal expansion rates of aluminum v. stainless and conclude (I think quite correctly) that it really doesn't make a difference for hobby applications. That said, when cutting an accuremote rule, I noted that behind the black strip is a thin strip of glass that carries the etched measurement markings. Thus, presumably, the comparison should be done between glass and whatever lurks below the surface of the igaging scale (which I have never opened)... just my $.02

    Harry in Maryland

    PS - I will mail the BlueSmirf today... sorry for the delay, but I was traveling.

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    1. Harry,
      I haven't cut the AccuRemote scales, so I can't definitively say one way or another, but the thin strip of glass is most likely fiberglass that is used as a substrate for circuit boards. If that is the case, the scales are the same, because iGaging has similar PCB. I doubt that AccuRemote use a solid glass strip.
      Thank you
      Yuriy

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    2. I'll email you a photo... I'm pretty sure it's glass... it's perfectly clear a shatters like glass. That's said, I'll take a closer look tonight.

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  6. I sent you a couple emails with pics... No doubt about it -- there's glass inside.

    Harry in Maryland

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    1. Harry,
      This is clearly different from the iGaing scales. The material used on those scales is definitely thin fiberglass. I don't know how this setups works, since glass has lower expansion index of stainless steel. I suspect the adhesive has a bit of give in it, or the scale would warp (similar to a bimetallic strip used in old thermostats, etc.). Never the less, this makes the encoder strip even more dimensionally stable. I think the difference is still mostly academic, though.

      Thank you
      Yuriy

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  7. Can the scales be cut to length? The 6in is too short and the 12 is too long. I want to cut a 12in scale down to approx 10in to fit the length of my atlas cross slide. I find my self moving the crosslide to its limits maybe when I have an indicator mounted to the tool post and dont want a scale thats too short to keep my range of motion hindered. The 12in scale would stick out an inch each end as the atlas cross slide is 10in. So im wondering if the scale is like a closed loop that would be rendered useless if trimmed down. Or is it safe to trim to my needs. Thanks.

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  8. Was this ever answered anywhere ??

    HWF

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  9. I just cut an AccuRemote stainless steel scale. It was a major pain. The material is really hard! I wore out two high-quality hacksaw blades.

    Doug

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  10. Cut one tonight and took the teeth off a hacksaw blade, bandsaw blade, and two sawsall blades. Finally cut it with a cut-off wheel in a Dremel tool.

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  11. Hi Yuri, I am using a Igaging DRO scale with Arduino UNO and your code. I only have the X-axis so far and I am looking the data using the serial monitor on my Arduino IDE. The scale is working fine with its own display, however, the output of your code is a huge integer (6digits always) and never stops... When I move the scale takes a while for the number to change, but again, it never stops in a value. Can you help me somehow?

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