iGaging AbsoluteDRO Plus Scales
iGaging AbsoluteDRO Plus scales pair a capacitive encoder with a stainless steel frame and a remote display. Compared to the older 21-bit EZ-View / DigiMag line, they hold position when powered off, run at a faster refresh rate, and handle shop noise noticeably better. On a TouchDRO system they connect through the iGaging scale converter and the same TDA-410 or TDA-420 adapter the rest of the lineup uses.
AbsoluteDRO Plus is our pick in the capacitive tier. It is especially well suited as a quill scale on a mill, where the absolute encoder means the quill always reports the right position even after the machine is turned off and back on. For a full multi-axis build, glass scales are usually the better answer; the section below goes into that tradeoff.
Scale Models and Naming
The line came in two distinct generations. The original iGaging AbsoluteDRO (without "Plus" on the label) used USB Mini-B and a proprietary data protocol that current TouchDRO firmware does not decode. Treat those as unsupported.
iGaging AbsoluteDRO Plus is the version TouchDRO supports. Early Plus units used USB Mini-B; later production switched to USB Micro-B. Internally they are the same scale — only the connector and the pin mapping changed. A generic Mini-to-Micro USB adapter will not work, because the AbsoluteDRO Plus pin functions don't match standard USB conventions for either connector. If you have an older Mini-B unit, see the pinouts in the Connecting section below.
Where AbsoluteDRO Plus Fits
iGaging AbsoluteDRO Plus scales are a great choice for a milling machine quill installation or a tailstock scale on a lathe. They offer very good performance for the price. The scales use a ground stainless steel frame, a thin-glass encoder strip, and a machined stainless steel head/carriage with an adjustable brass gib strip. As a result, they are much more accurate and repeatable than the plastic-on-extruded-aluminum scales. Although AbsoluteDRO Plus scales use Mitutoyo's SPC protocol, they have a few advantages over Mitutoyo's own quill scales. First, the scale is powered directly from TouchDRO and is always on when TouchDRO is on — no surprises when a battery dies or the scale goes to sleep on a timeout. Second, and more important, is the data transfer rate. AbsoluteDRO Plus currently has the fastest refresh rate on the market, at 50 readings per second, compared to about 10 per second for Mitutoyo quill scales.
That said, these scales are not the best choice for a full machine setup. Like most capacitive scales, their maximum resolution is 10 µm (about 0.0004"). At a price comparable to entry-level glass scales, and outside of the convenient form factor, glass scales are superior in almost every regard. They offer at least twice the resolution, better environmental protection, and usually have repeatable reference marks. For a full DRO build, glass scales are usually the better value. The Recommended DRO Scales guide covers the glass and magnetic options.
Connecting AbsoluteDRO Plus to TouchDRO
iGaging AbsoluteDRO Plus scales with USB Micro-B (also called Micro-USB) connectors can be connected to TouchDRO using an iGaging scale converter. The scale's Micro-USB cable plugs into the converter; the converter provides a dedicated 3.3V power supply and conditions the signals that go to the TouchDRO adapter. You will need one converter per axis.
If you have an older Mini-B scale, use the pinouts below to wire it to the Micro-B layout the converter expects, either by re-terminating the cable or by building a Mini-B-to-Micro-B adapter cable.
USB Pinouts
The Mini-B and Micro-B pinouts are not the same, and neither matches typical USB power/data conventions. Match the right table to the connector your scale actually has before applying power.
| USB Mini-B Pin | TouchDRO line |
|---|---|
| 5V | Ground |
| D– | Data |
| D+ | Clock |
| ID | 3.3 V |
| GND | Ground |
| USB Micro-B Pin | TouchDRO line |
|---|---|
| 5V | 3.3 V |
| D– | Clock |
| D+ | Data |
| ID | Ground |
| GND | Ground |
Technical Details
| Power supply voltage | 3 V |
|---|---|
| Scale frame connection | Ground |
| Resolution | 10 µm / 0.00039" |
| Material | Stainless steel |
| Accuracy | 0.001"/6" |
| Refresh rate | Up to 50 Hz |
| Available lengths | 6", 12", 24", and 36" |
Data Format and Protocol
AbsoluteDRO Plus scales use the Mitutoyo SPC (Digimatic) protocol verbatim — the same serial format Mitutoyo runs on its own digital instruments. The iGaging scale converter handles the protocol and presents the decoded position to the TDA-4xx adapter, so the data format is not something you need to deal with directly.
Summary
For a quill scale on a mill or a tailstock scale on a lathe, AbsoluteDRO Plus paired with the iGaging scale converter is the setup we recommend to most customers. The scales are very accurate and repeatable, run at 50 Hz, and need no battery management. For a full multi-axis DRO build, glass scales are usually the better value. The Recommended DRO Scales guide covers those.