Mitutoyo Optical & Magnetic Scale Pinouts

Mitutoyo optical and magnetic DRO-style linear scales are well-regarded for accuracy and durability. They show up on the used/secondary market pretty often — sometimes at prices that make them a really nice upgrade compared to many other industrial-scale options. Many modern and legacy Mitutoyo DRO-style scales can be used with TouchDRO, but the details depend on the output type. This page focuses on these DRO-style scales (the kind used with traditional DRO counters). For information about Mitutoyo’s Digimatic / SPC scales (calipers, micrometers, indicators, etc.), see: Mitutoyo Digimatic / SPC scale pinouts.

Output Types (What Your Scale Sends Out)

• Quadrature (RS-422 / differential) — the “standard DRO” A/B signals (often with Z/reference). Compatible with TouchDRO.
• Sin/Cos (2 Vpp single-ended) — needs an interpolation circuit to convert to quadrature.
• Sin/Cos (1 Vpp differential) — also needs an interpolation circuit (different electrical format than 2 Vpp).
• Absolute (proprietary) — model-specific protocol; not currently supported by TouchDRO.

In general, 5 V-powered quadrature scales are the most straightforward: if the scale outputs RS-422 style A/B (and sometimes Z/reference), you typically just need an adapter cable (or a connector swap). Many Sin/Cos (Vpp) scales can also be used, but they require a comparator circuit or an interpolation box to convert the analog signals into quadrature.

Connectors You’ll See in the Wild

Most modern Mitutoyo DRO-style scales use a 15-pin D-Sub (DB15) connector (typically a DB15 male on the scale), but there are at least six different DB15 pinout schemes used across the current scale families.

You may also run into Mitutoyo scales with round multi-pin connectors. A 6-pin round connector is fairly common on some older scales. In many cases these scales are electrically compatible with the modern families, and some can be used with TouchDRO with the right adapter cable. A 7-pin round connector usually shows up on older systems and is often not directly interchangeable — and we currently have limited confirmed pinout data for those variants.

Finally, some scales come with OEM-specific harnesses (pigtails or proprietary connectors), since Mitutoyo supplies these scales to various equipment manufacturers. These scales often show up on the used market at a very attractive price, but it’s usually hard to figure out the exact scale model and pinout.

Current Mitutoyo Scale Connection Information

To figure out your scale’s pinout, you first need to determine exactly which model you have. For the AT scale family, the model number is usually etched or printed on the scale’s frame. The ST family can be trickier — Mitutoyo often prints only the family name on the reader head (ST36, for example), but to determine the pinout you need to know the variant (ST36A vs ST36C, and so on).

If you can’t find the full model name, try opening the DB15 connector and cross-checking which pins are actually populated against the pinout table below. In many cases, you can narrow it down to A, C, or B/D.

Scale Output Types and TouchDRO Compatibility

If your scale is in the RS-422 quadrature bucket, hooking it to TouchDRO is pretty straightforward: you’ll just need an adapter cable. A simple DIY version can be made from a DB15 female, a DB9 male, and an 8-conductor cable (plus shield/drain if your scale cable uses one).

DB15 Pinout Options

The table below is a quick reference for the common DB15 pinout profiles used by the AT2xx, ST, and AT1xx families. Note that ST scales use multiple “Type” pinouts, so matching the model/variant to the correct pinout matters.

Connecting RS-422 Scales to TouchDRO

If you want the best performance (and an easy way to take advantage of the Z/reference signal), we recommend using one of the pre-built TouchDRO TDA-4xx adapters: TDA-410 Plus (lathe) or TDA-420 Plus (mill). If you’re building a DIY adapter, you can also keep things really clean by using DB15 connectors on your enclosure and wiring the scales directly to your TouchDRO DIY board (no custom DB15→DB9 pigtail needed): TouchDRO DIY DRO Kit (TDK-40).

To connect your scale to a TDA-4xx adapter, you will need a DB15→DB9 cable, that uses a DB15 female (scale side) and a DB9 male (TouchDRO side). You’ll need 8 conductors total: A+/A−, B+/B−, Z+/Z− (three twisted pairs), plus +5 V and 0 V (GND). Wire “like to like” (A+→A+, A−→A−, etc.). On the DB15 side, tie the +5 V pins together and tie the ground pins together (they’re usually not tied internally inside the scale). A shielded Ethernet cable works fine as long as each differential pair stays on a twisted pair (A with A′, B with B′, Z with Z′). Before plugging anything in, check the finished cable with a multimeter for continuity and shorts.

Connecting Sin/Cos Scales to TouchDRO

Common wiring notes

• Verify before powering. Wrong +5V/0V mapping can damage a scale.
• Vref matters. Some counters/interfaces use it as a bias/reference; don’t ignore it.
• Shield / frame ground: Pin 15 (F.G) is typically frame ground / shield termination; bond per your grounding scheme.
• Aux lines: ALM / PA / PB / PZ are auxiliaries unless your exact integration requires them.

DB15 Absolute / Proprietary Serial (RS-485-ish)

Some Mitutoyo scales use a proprietary digital protocol that is not standard quadrature. These are often absolute-type systems and typically require model-specific documentation and/or interface units.

What we know (and what we don’t)

• Physical layer: often RS-485-ish (model dependent)
• Protocol: proprietary framing (not SPC, not quadrature)
• Wiring: DB15 shell does not imply compatibility with other DB15 Mitutoyo scales

Known pins fragment (from available notes)

The fragment below is useful for identifying power/ground/data on a known harness. It is not a complete universal pinout.

Known models in this family (per Mitutoyo docs / manuals)

• (TODO — list models once we group the extracted pinouts)

Connector Types, Wiring Notes, and Common Issues

Connector types

• DB15 is common across multiple Mitutoyo families, but signals differ by model/family.
• Round 6-pin / 7-pin connectors appear on some older Mitutoyo scale families and OEM integrations — the connector still does not imply a specific signal type.
• Some models use other connectors or OEM harnesses depending on the machine integration.
• Cable part numbers matter — in some systems the cable/interface unit effectively defines the pin usage.

Wiring notes

• Verify before powering. Wrong +5V/0V mapping can damage a scale.
• For differential signals, keep twisted pairs together and maintain shielding where possible.
• Bond shield/drain per the machine/control cabinet grounding scheme (often frame ground at one end).

Common issues

• “DB15 means it should work” — false; DB15 is shared across incompatible interfaces.
• Model confusion — similar housings across different electrical families; the label/model number matters.
• Cable mismatches — swapping Mitutoyo cables between families can silently miswire power or signals.