iGaging 21-Bit Linear Scales
Overview
The classic iGaging DigiMag RemoteDRO scales appeared on the market in the early 2010s. They quickly gained popularity thanks to their use of a separate display that could be mounted remotely and could thus be used as a make-shift digital readout. The scales appear to have been manufactured by Sanhe Measuring Instrument Co., Ltd. and were available in other countries under the Shahe brand. Around the same time, these scales appeared with an upgraded stainless steel frame and encoder housing under the AccuRemote DRO brand, as well as in stainless steel and aluminum versions under the Shars brand. A few years ago, iGaging upgraded the display unit to the one previously used by their AbsoluteDRO scales and rebranded DigiMag to EZ-View DRO and then to EZ-View DRO Plus.
The difference between the different brands is mostly on the exterior. Besides the difference in the frame material and encoder housing, the plastic color varies by brand. For instance, AcccuRemote DRO and Shars use blue plastic, while iGaging first used black plastic and then switched to black/gray color scheme. Another difference is the connector type used in the display unit. Initially, iGaging used USB Mini-B cables but later switched to Micro-B, while the others appear to have stuck with Mini-B cables. Notably, the pin functions remained the same, allowing the use of Mini-to-Micro adapter to connect older scales to the TouchDRO adapter that uses Micro-B connectors.
For the sake of brevity, the remainder of this page will refer to all 21-bit scales as "iGaging EZ-View".
Scale Brands and Models
- iGaging EZ-View DRO
- iGaging EZ-View DRO Plus
- iGaging DigiMag Remote DRO
- AccuRemote DRO
- Shars Digital Aluminum Machine Scale
- Shars Digital Stainless Steel Machine Scale
How to Identify
The frame and the reading head housing used by these scales are similar to those used by the newer Shahe scales, so the most reliable way to identify these scales is to examine the display unit. EZ-View DRO scales are the easiest to recognize by their distinct display housing and very prominent iGaing branding. The branding of the older iGaging DigiMag Remote DRO scales is more subtle and includes only the iGaging logo on a sticker. The display used by other brands is made using the same molds and differ only in the color and branding sticker.
Differences with New Shahe Scales
Recently, Shahe started offering "Remote DRO" scales that are completely different and incompatible with 21-bit adapter firmware. At first glance, they are similar and are often confused with the DigiMag scales. As you can see in the photo below, there are obvious differences between the two display units.
Technical Details
| Power supply voltage | 3V |
|---|---|
| Scale frame connection | Ground |
| Data Format | 21-bit, proprietary |
| Resolution | ~10 micron/0.00039" |
| Material | Aluminum or Stainless Steel |
| Accuracy1 | Aluminum: 0.006"/6" Stainless Steel: 0.0015"/12" |
| Refresh rate | Up to 50Hz |
| Available lengths | 6”, 12”, 24”, and 36” |
1 Accuracy as reported by the scale manufacturers is largely a meaningless parameter, especially when the scales are used in conjunctions with TouchDRO. Please refer to the "How to Select Scales for DIY DRO" page for more info about important technical specs.
Data Format and Protocol
These scales use a unique 21-bit data format that doesn't appear to be used by any other scale manufacturers. The position is represented using 21 bits in two's complement format, making it relatively easy to decode.
Another unique feature of these scales is how the data clock is provided. In contrast to virtually every other scale model on the market, the EZ-View scale encoder doesn't provide its own data clock and relies on the display unit to initiate the data stream and provide the clock signal similar to how SPI communications work. Curiously, these scales use a peculiar resolution that is neither metric nor imperial, with 2560 divisions per inch, which is a bit finer than 10 microns.
Connection Scheme
As mentioned earlier, these scales come with USB Mini-B and USB Micro-B connectors. Although they appear to have the cable hard-wired into the reading head, it isn't so. Under the plastic cover, there is a surface mounter female USB connector into which the cable is plugged in and secured with a dab of hot glue.
Fortunately, both Micro-USB and Mini-USB versions use the same pin mapping, so adapting a Mini-B scale to a Micro-B TouchDRO adapter is relatively easy by using a Mini USB female to Micro-USB male adapter or replacing the whole cable with Mini-USB Male to Micro-USB male. In the latter case, you might need to shave some plastic off the connector to make it fit flush into the board-mounted connector.
USB Pin Functions
| USB Pin | TouchDRO Line |
|---|---|
| 5V | 3.3V |
| D- | Clock |
| D+ | Data |
| ID | Not Connected |
| GND | Ground |
Hard-Wiring the Cables
When using a DIY DRO adapter, many people opt for simply cutting the connector off and soldering the cable to the PCB. This provides a simple and secure connection, provided there is adequate strain relief. If you decide to use this approach, please keep in mind that there is no standard conductor color scheme. This means that you will need to use some other way to figure out which wires carry which signal.
Fortunately, there are clearly marked test points on the PCB. By testing the continuity between them and the wires you will be able to reliably identify the signal lines.
| Test Point | TouchDRO Line |
|---|---|
| VDD | 3.3V |
| DATA | Data |
| SSY | Clock |
| Scale Frame | Ground |
TouchDRO Compatibility
- Pre-made TouchDRO Adapter board for iGaging/Shahe Scales 2
- MSP430G2 Launchpad running "Basic" TouchDRO Firmware
- MSP430G2 Launchpad running "Mixed Scale" TouchDRO Firmware
- Arduino (ATMega328 variants) using the sketch maintained by Rysiu M.
2 The adapter board comes with pre-installed USB Micro-B connectors. Scales that use USB Mini-B connectors will need to be connected using a set of Mini-USB breakout boards, Mini-to-Micro adapters, or soldered directly into the board.
Pros
- Fast refresh rate
- Simple data format and communication protocol
- Multiple TouchDRO connection options
- Consistent connection scheme between Mini and Micro USB versions
Cons
- Limited availability outside of the USA
- Slightly higher price compared to new Shahe scales
- Last digit prone to flicker if a scale is stopped in between encoder ticks
Final Words
iGaging EZ-View DRO, DigiMag Remote DRO, or Shars Digital Aluminum Machine scales are a great option for a budget digital readout thanks to their 3V power supply, simple data format, and fast refresh rate. AccuRemote and Shars Digital Stainless Steel Machine scales are more durable and have better repeatability, but cost significantly more and approach the price of low-end glass DRO scales.