DRO Scale Signal Families & Output Types

Understanding your scale’s signal type is the most important step in connecting it to TouchDRO. Scales that look identical on the outside can use completely different electrical outputs on the inside. This section groups scales by how they communicate electrically, not by how they’re built (glass vs. magnetic, etc.).

A common point of confusion is the physical connector. A “monitor-style” 9-pin, 5-pin round connector, USB-looking plug, or any other connector shape does not reliably tell you what the scale outputs. Many manufacturers (and especially import sellers) reuse the same connectors across different product lines, and adapters/cables are often swapped or re-terminated.

Likewise, the brand name and the scale’s external appearance are not reliable indicators. Two scales can look nearly identical and still use completely different outputs (quadrature, SPC/Digimatic, sin/cos 1Vpp/2Vpp, or a proprietary protocol). The only dependable way to choose the right TouchDRO hardware is to identify the signal family.

Once you know your signal family, choosing the correct TouchDRO adapter and wiring method becomes straightforward. Click a signal type below to see examples, oscilloscope captures, and TouchDRO-specific connection notes.

Signal Families

Incremental Quadrature (TTL / RS-422) more

This is the most common output type found in modern DRO scales. Most import optical glass scales and magnetic scales use incremental quadrature, and every major high-end manufacturer offers at least a few models in this category. The scale outputs two digital square waves (A and B) that indicate motion and direction; some models also provide a reference/index signal (often labeled Z or R).

Most quadrature scales use a 5 V supply and produce 0–5 V logic-level signals, which TouchDRO supports natively. If you run into a scale that uses a different logic voltage, it can often be adapted with the appropriate interface hardware (for example a level shifter, line receiver, or (in some cases) a resistor divider).

Output drivers vary by model. Most modern scales use push/pull (actively driven high and low) outputs. Some older or industrial scales use open-collector (or open-drain) outputs, which require pull-up resistors and careful attention to input compatibility.

  • Most glass DRO scales
  • Most magnetic DRO scales
  • Rotary encoders

TouchDRO compatibility: Incremental quadrature is the native signal format TouchDRO is designed around. All TouchDRO adapters and common DIY builds support A/B signals directly (TTL and RS-422). The TDA-4xx family also supports multiple common reference/index (Z/R) formats, including single-ended and differential reference signals.

Recommended hardware:

Sin/Cos Analog (1Vpp / 2Vpp) more

High-resolution analog encoder signals based on sine and cosine waveforms. These are typically specified as 1Vpp or 2Vpp in documentation and are most commonly found in high-end industrial equipment, inspection systems, CMMs, and precision machine tools. Compared to quadrature encoders, sin/cos systems offer significantly higher native resolution, but they also require more sophisticated interface electronics.

Rather than producing digital pulses directly, the scale outputs two analog waveforms that must be processed by an interpolator. The interpolator converts the analog sine and cosine signals into high-resolution quadrature pulses. This is how sin/cos systems achieve their extremely fine positioning resolution.

You'll also see sin/cos encoders in precision motion systems outside of machine tools—for example some microscope stages (including systems built around Renishaw's RGH22 readhead family).

At present, sin/cos scales can be connected to TouchDRO only through an external interpolation unit. Many manufacturers offer interpolator boxes designed specifically for their own scales. It is also possible to build a custom sin/cos-to-quadrature converter, but this is an advanced project that requires careful signal conditioning and calibration to preserve the full resolution of the encoder.

  • Heidenhain encoder systems
  • Mitutoyo AT1xx series
  • High-end industrial glass and tape scales
  • Some Renishaw encoder/readhead systems (e.g., RGH22 family)

TouchDRO compatibility: Native support for sin/cos encoders is coming in the first half of 2026. TouchDRO is developing both an interpolation adapter and a simpler sin/cos-to-quadrature converter that will allow these scales to be used directly with TouchDRO while preserving their high resolution.

SPC / Digimatic more

A serial digital protocol used by calipers and many compact DRO scales. Instead of producing motion pulses (like A/B), these scales transmit position data in timed digital frames. Depending on the device, the data may be streamed continuously or sent only when the scale is polled.

This family includes Mitutoyo Digimatic/SPC scales and many "SPC-compatible" products (including several iGaging and Starrett models). Note that "SPC" describes the interface/protocol—not the mechanical construction of the scale. To connect SPC/Digimatic scales, you typically need a compatible output cable (the scale side connector is often proprietary) and the correct signal-level converter to match TouchDRO inputs.

Electrical output styles vary. Many Mitutoyo SPC devices behave like open-drain/open-collector outputs and can be interfaced with a simple circuit (often just pull-ups/pull-downs and proper level shifting). Some devices output push/pull signals and may require a more robust input stage to ensure clean logic levels and avoid stressing either device.

  • Mitutoyo Digimatic / SPC scales
  • iGaging Absolute DRO Plus and other SPC-style scales
  • Starrett and other SPC-compatible brands

TouchDRO compatibility: Supported across TouchDRO using the appropriate converter (or a simple DIY interface circuit when the signal levels match).

Converters:

Related:

Proprietary Protocols more

Manufacturer-specific digital formats that do not follow standard quadrature, sin/cos, or SPC conventions. These typically require model-specific documentation to evaluate compatibility.

  • Mitutoyo AT7xx magnetic scales
  • Some Renishaw systems
  • Specialized industrial encoders

TouchDRO compatibility: Model-dependent. We're actively investigating support for selected protocols (for example AT715), but this is a long-term effort.

How to Identify Your Scale's Signal Type

  1. Check the scale's datasheet or manual (look for terms like TTL, RS-422, 1Vpp/2Vpp, Digimatic/SPC, etc.).
  2. Look for signal labels on the connector or cable (A, B, Z/R, +5V, 0V, CLK/DATA, etc.).
  3. Search the Pinout Library for known families and common wiring patterns.
  4. If documentation is missing or unreliable, follow the reverse-engineering guide for safe identification.

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