Documentation / Integrations / Digimatic

I — The wire

A Digimatic frame is a number with a unit attached

The SPC output on a Mitutoyo caliper, micrometer, indicator or height gage sends thirteen nibbles (fifty-two bits) carrying a value, a sign, a decimal position and a unit. It carries nothing else. Everything a quality record needs beyond the number has to be supplied by the layer above the gage.

Frame layout verified against an independent open-source decoder

Digimatic is a synchronous, gage-clocked interface distinct from RS-232 and UART: host-requested frame across three logical lines: the host pulls REQ low to ask, the gage drives CLK, and DATA is sampled against that clock. The whole transaction completes in tens of milliseconds, which is far faster than any human-triggered workflow will ever ask for. Throughput is not a constraint anywhere in this category, and a product selling on read speed is selling against a problem that does not arise here.

II — The frame

Nibble	Contents
0–3	Preamble. All four read `0xF`; a frame where they do not is discarded rather than interpreted.
4	Sign. `0` positive, `8` negative — and no other value is legal.
5–10	Six BCD digits, most significant first. This is the measurement.
11	Decimal point position — the number of places, applied as a divisor.
12	Unit flag. `0` millimeters, `1` inches.

Read that table again as an inventory. Six digits, a sign, a decimal place and a unit. A decoder written against this protocol returns a reading and a unit because there is nothing else in the frame to return.

III — What is not in it

Every one of the following has to be manufactured somewhere above the wire:

Instrument identifier
Serial number
Instrument model or type
Timestamp
Calibration status or due date
Characteristic or feature reference
Nominal and tolerance
Part, lot or job context
Operation or station
Operator identity
Resolution as distinct from displayed places
Battery or signal health

The consequence is not academic. When a gage is found out of tolerance at its next calibration, the question that matters is which parts it measured in the interim. That is a query only if instrument identity was bound to each reading at the moment of capture. It cannot be reconstructed afterwards from a stream of anonymous numbers, no matter how good the records system is.

IV — Where identity actually comes from

It comes from the port rather than the gage. “The instrument on channel 3 is the 0–25 mm micrometer, asset MIC-0042” is a fact that lives in an interface box’s configuration or in software. It is typed by a person, and it goes stale the moment a gage is swapped, moved, or sent out for calibration.

Wireless does not change this by itself. A Mitutoyo U-WAVE-T clips onto the Digimatic port and converts the same frame to a 2.4 GHz packet, so it inherits the frame’s metadata poverty exactly, whatever identity exists in a U-WAVE deployment is identity the receiving side assigns. Where that assignment becomes machine-readable is at the receiver: pairing a transmitter on an individual channel rather than the global one lets the base remember the transmitter’s identity and report it alongside the reading. The MobileCollect EVO specification covers that path in detail.

gage        → value, sign, decimal position, unit
transmitter → the same frame, over radio
receiver    → the reading, plus which channel it arrived on
software    → everything else, or nothing

V — Why this decides whether a study means anything

A keyboard wedge is the cheapest useful intervention in shop-floor capture, and SVEND accepts one directly: see the digital gage input contract. But it is worth being precise about what it does and does not fix. A wedge removes the transcription error, because the number that reaches the field is the number the gage displayed. It does not know which feature the number belongs to, and it does not know which instrument sent it, because neither fact is in the frame.

That second gap is why a run sheet matters more than it looks. A study whose readings were typed from a clipboard is, in part, a study of the typing. Binding the row before the reading arrives (the sheet knows which part, which appraiser and which trial the next value belongs to, and advances by run rather than by whatever field has focus) is what designs the assignment error out instead of hoping against it. That is the contract the Gage R&R study bench implements.

VI — Sources

Frame layout, preamble check, sign encoding, BCD digits, decimal position and unit flag verified against vifino/CircuitPython-mitutoyo, an independent open-source Digimatic decoder.
U-WAVE radio, transmitter families and topology from Mitutoyo’s own U-WAVE documentation.
Receiver-side identity behavior from MicroRidge’s MobileCollect EVO API implementation guide.

Mitutoyo, Digimatic, U-WAVE, MicroRidge and MobileCollect are names of their respective owners. Nothing here implies review, certification, sponsorship or endorsement by any of them.

Digital gage input → MobileCollect EVO → Gage R&R study bench →