A finer position increment looks attractive on a specification sheet, but it also changes the demands on the receiving electronics when an axis moves. Before selecting optical linear encoders for a measurement-stage project, we check the output format, the meaning of resolution and the counter input specification together. Matching only the connector or supply voltage leaves an important question unanswered: can the receiver reliably recognise the signals at the intended travel speed?

Application demonstration: the cover and video show our vertical and horizontal vision measurement equipment. They illustrate dimensional inspection, not the identity of its installed encoder or a test of encoder bandwidth. The numerical example below is an interface calculation, not measured equipment performance.

Separate the market headline from the selection calculation

Renishaw’s trading update dated 22 October 2026 reported strong demand in position measurement, including open optical and laser encoders for semiconductor equipment. Its 47% year-on-year revenue increase refers to the group; it is not an industry-wide encoder demand figure. Such news can explain renewed interest in position feedback, but it cannot choose a suitable interface for an individual machine. That decision still starts with the signal and receiver specifications.

When we discuss exposed linear encoders, we distinguish the scale’s physical pitch from the interpolated output increment. Interpolation can provide a finer reported displacement without changing the underlying scale pitch. We also distinguish that increment from measurement accuracy. A system displaying more decimal places has not thereby demonstrated smaller total measurement error, particularly when alignment, temperature, machine geometry and the complete inspection method remain relevant.

Define what one count means

Digital incremental quadrature commonly provides two channels, A and B, with a phase relationship that indicates motion direction. Depending on the receiver, counting may use one edge, two edges or all four edges per signal cycle. A specification expressed in cycles per second is therefore not automatically comparable to one expressed in counted edges per second. We write down the counting convention before comparing headline frequency values.

For incremental encoders with a digital output, a useful starting calculation is counted-edge rate equals axis speed divided by displacement per counted edge. Both terms must describe the same configured counting mode. The reference or index signal is a separate function; adding an index does not increase the receiver’s ability to count the A/B transitions. We also check the reference capture requirements if it is used during machine operation.

Work through one explicit example

Assume, purely for illustration, that an axis travels at 0.1 m/s and each counted quadrature edge represents 0.5 micrometres. Converting speed gives 100,000 micrometres per second. Dividing by 0.5 gives 200,000 counted edges per second. If those increments come from four-edge decoding, the corresponding A/B waveform cycle frequency is 50,000 cycles per second. These two frequency figures describe the same example under different conventions.

Reducing the displacement per counted edge to 0.1 micrometres at the same speed would raise the counted-edge rate to 1,000,000 per second. This is not a claim about a particular HANDING product. It shows why a resolution change must trigger another interface check. We cannot approve a counter merely because its advertised frequency exceeds one of these numbers without first checking what that frequency actually specifies.

The ideal rate is only the first check

The encoder output stage and the receiving electronics have their own timing requirements. Minimum edge separation, pulse width, input filtering, cable effects and the permitted signal conditions can constrain operation. We compare the manufacturers’ definitions and allow the margin required by the actual design, rather than calculating an ideal limit and treating it as a guaranteed machine speed. Testing at a slow traverse does not establish behaviour during the fastest return move.

With digital linear encoders, we review the exact signal variant and the receiver’s compatible electrical input. A differential signal should be received using the specified interface, with appropriate cabling and termination. Plug compatibility does not establish electrical compatibility. Changes to extension cables, routing or input filtering should be recorded because they can alter the system conditions that were originally checked.

Do not apply the quadrature formula to every interface

An analogue sine/cosine output requires a suitable interpolation and acquisition path, with its own analogue bandwidth limits. A serial absolute interface involves protocol timing, update rate and receiver compatibility. Neither should be approved by simply reusing a digital quadrature edge-rate calculation. Where alternative signal variants are offered, we ask for the complete ordering configuration so that the interface under review is unambiguous.

In an Automatic Video Measuring Machine project, the fastest mechanical traverse and the exposure or measurement phase may also be different operating conditions. We review both the position feedback during motion and the inspection result at the intended measurement condition. Satisfying an electrical counting limit does not prove image quality, settling behaviour or dimensional accuracy. Each belongs in its own part of the equipment acceptance plan.

Keep an interface record that survives an upgrade

Our selection record includes output type, increment definition, counting convention, required speed, receiver specification and cable arrangement. It should also identify which settings were actually tested. After a resolution or controller change, the old record is a starting point for review, not automatic approval of the new configuration. Comparison of position readings over a controlled travel can support the investigation, while a complete accuracy evaluation still requires an appropriate measurement method.

For a Vision Measuring System enquiry, send the required inspection task and available controller information to handing3d@163.com. We can discuss equipment options while checking position feedback as part of the complete system. The practical aim is to choose a useful measurement increment that the actual electronics can handle, then verify the dimensional performance required by the application.

Technical references: Renishaw optical encoder FAQs; Renishaw trading update, 22 October 2026.