Overview of Capacitive DRO Scales
Capacitive linear scales have been popular with budget-conscious home machinists for the better part of three decades. The main appeal of capacitive scales is their low cost, which gives hobbyists access to a functional digital readout (DRO) for a fraction of the cost of an off-the-shelf DRO. On top of that, these scales can be easily cut to the needed size, making them preferable for smaller milling machines and metal lathes. As is the case with all DRO scales, capacitive scales have their pros and cons, so it's important to have at least a cursory understanding of the most important DRO scale characteristics.
There is a large number of capacitive scale models on the market offered by several manufacturers. While they might look similar on the outside, there are many important internal differences between capacitive DRO scales, including data format, communication protocol, and power supply voltage. The good news is that TouchDRO can interface with the vast majority of Chinese linear scales on the market, but different scales have different adapter hardware and firmware requirements. To make sure that you select a compatible combination of scales, TouchDRO adapter, and firmware, please refer to the list below.
If you are simply trying to decide which scales to buy for a new DRO installation, start with the Recommended DRO Scales for TouchDRO guide. It provides practical suggestions for mills and lathes and links to the appropriate adapters.
Supported Scales
TouchDRO relies on custom adapter firmware to interface with various models of capacitive scales. At the time of this writing, most mainstream linear scales and a number of other specialty scales are supported. Each scale family has different interfacing hardware requirements and decoding firmware. The list below contains details about supported capacitive scale families, their important characteristics, and TouchDRO adapter compatibility.
iGaging Absolute DRO Plus
iGaging Absolute DRO Plus scales use a true absolute encoder and a stainless steel frame/encoder housing along with the large stackable display. These scales are incompatible with other iGaging capacitive scales since they use a completely different data format and communication protocol.
For most new TouchDRO installations that use capacitive scales, iGaging Absolute DRO Plus is the preferred choice. These scales are fully supported by the current generation of TouchDRO adapters and the TouchDRO Plus firmware, and are featured in the Recommended DRO Scales for TouchDRO guide. If you are starting from scratch and want a proven, well-supported scale family for your mill or lathe, this is usually the best place to start. View the detailed iGaging Absolute DRO Plus guide
There is an older version of Absolute DRO scales without the “Plus” designation that uses a completely different data protocol and is incompatible with TouchDRO.
iGaging EZ-View DRO Plus
iGaging EZ-View is the updated version of the classic iGaging DigiMag Remote DRO scales. The scales use an extruded aluminum frame with an injection-molded plastic reading head and a large stackable display. Ignoring the difference in the display, these scales are basically identical to their predecessor and use the same data format and interface.
EZ-View scales are supported by TouchDRO via the dedicated capacitive-scale firmware and compatible adapters. For details about wiring, connector pinout, and adapter compatibility, see the iGaging / DigiMag 21-bit scales compatibility guide.
iGaging DigiMag Remote DRO
iGaging DigiMag was the first capacitive scale model with a display that can be mounted remotely. They use an extruded aluminum frame in conjunction with an injection-molded plastic transducer housing. The display is connected to the reading head using an USB cable that is glued to the transducer board and has a male plug on the display end. The scales are powered via two 3 V cells connected in parallel.
TouchDRO supports DigiMag scales using the same adapter and firmware as EZ-View and other 21-bit iGaging-style scales. For installation tips and electrical details, refer to the DigiMag / EZ-View 21-bit scales setup guide.
These scales were sold in some parts of the world under the Shahe name or even without branding. They were identical to the iGaging version, unlike the newer Shahe 4304-xxxA scales (shown further down) that use similar displays but are completely different and incompatible.
AccuRemote DRO
AccuRemote DRO scales are rebranded and upgraded DigiMag-style scales. They are electronically identical to the iGaging DigiMag / EZ-View scales but use a precision ground stainless steel frame with a machined stainless steel encoder housing along with blue plastic trim.
Because the internal electronics and data format match the 21-bit iGaging scales, these AccuRemote scales work with the same TouchDRO adapters and firmware. See the AccuRemote / iGaging 21-bit compatibility and wiring guide.
Shars Digital Machine Scale
Shars Digital Machine Scales are another example of rebranded DigiMag-style scales. These scales come in two flavors: with an extruded aluminum frame and plastic encoder housing similar to the iGaging DigiMag scales, and with a stainless steel frame and encoder housing similar to the AccuRemote DRO scales.
As long as the internal electronics match the common 21-bit iGaging pattern, these scales are supported by the same TouchDRO adapters and firmware as other DigiMag/EZ-View/AccuRemote scales. For specifics on pinout, power, and supported adapters, see the Shars / iGaging 21-bit scale compatibility guide.
Shahe Digital Linear DRO Scales with Round Display
The “Round Display” linear DRO scales (model 5403-xxx) are manufactured by Sanhe Measuring Instrument Co., Ltd. and have been introduced to the market relatively recently. Just like iGaging DigiMag and EZ-View, Shahe scales use an extruded aluminum frame and plastic housing, and are powered by a 3 V battery. Internally, they use a completely different encoder strip and send the data in BIN6 format. Also, a notable fact is that these scales have the cable hard-wired into the display; on the other side, some samples come with a USB connector while others come hard-wired into the reading head as well.
TouchDRO supports these Shahe scales using dedicated firmware that understands the BIN6 protocol. Before purchasing, make sure your adapter and firmware version explicitly list Shahe 5403 support. See the Shahe 5403 DRO scale details
Shahe Digital Linear DRO Scales with “Square” Display
The “Square Display” version of the scales (model 5403-xxxA) is similar to the “Round Display” model but uses a display that is visually similar to the iGaging DigiMag scales. Internally both Shahe models are identical. They rely on the same encoder strip and PCB and transmit the data in the same BIN6 format but have some minor mechanical differences.
From the TouchDRO point of view, both Shahe models are handled the same way and use the same adapter and firmware. Mechanical packaging is the main difference; pick the version that best fits your machine and mounting constraints. View the Shahe round vs. square display comparison
Shahe Vertical Type Digital Linear Scale
These scales are based on the same encoder and use the same data format as the Shahe “Digital Linear DRO Scales” but have a few notable differences. They use a precision ground stainless steel frame with a machined stainless steel housing, a display that is built into the reading head, and a USB data port. Even though these scales are powered by a 3 V cell, the data stream is scaled down to approximately 1.5 V, which affects how they must be interfaced with a DRO adapter.
TouchDRO can work with these vertical Shahe scales using the same BIN6-capable firmware, but pay attention to the signal voltage and wiring details described in the documentation. Read the Shahe vertical scale interfacing guide
Generic Chinese Linear Scales
This family includes many different scales from a number of manufacturers. These scales generally use a stainless steel frame and encoder housing and are powered by a single 1.5 V button cell battery. They use the traditional 4-pin caliper data port. Some of these scales might look like digital calipers with their jaws removed, but in most cases, they come with purpose-built displays, either vertical or horizontal.
TouchDRO supports many of these 48-bit Chinese scales via the BIN6/BIN48-capable firmware. Because internal electronics can vary, be prepared to verify pinout, signal levels, and data format before committing to a full installation. Read the 48-bit Chinese DRO scale guide
Inexpensive Digital Calipers
Almost all inexpensive Chinese digital calipers on the market use the same 4-pin data port as the generic Chinese scales mentioned above and are powered from a single 1.5 V button battery. Some manufacturers also sell linear scales that use the same frame and electronics but have the jaws removed and mounting holes added.
While digital calipers are not as robust or convenient as dedicated machine scales, they can be a very cost-effective way to add a basic DRO to a small mill or lathe. TouchDRO can read their data stream using the appropriate capacitive-scale firmware and adapter. Learn how to use digital calipers as DRO scales