Introduction

Two letters decide a machine's behavior every time the power cycles: inc or abs. The incremental-vs-absolute decision is one of the oldest in motion control, yet it still drives surprised faces on commissioning day — the axis that "forgot where it was" and now demands a full homing routine before it will move. For procurement engineers and OEMs, the choice is not about which is "better" but about which matches how the machine is allowed to behave after a reset, a fault, or a power cut.

This article draws the line between incremental and absolute encoders in operational terms, anchors the difference to real TIMSENS time-grating specifications — including absolute position by nature, multiturn memory up to 65,535 turns, and no battery dependency — and gives a clear rule for when you must specify absolute.

The Operational Difference

An incremental encoder reports change in position: A/B quadrature pulses plus a Z index. It knows how far it has moved since it started counting, but it does not know where it is in absolute terms until it finds the index. On power-up, the controller's position register is empty.

An absolute encoder assigns a unique digital code to every position across the full range. The controller reads the true angle or displacement the instant communication starts — no counting from a reference, no index search.

The whole difference collapses to one question: after a power loss, does the axis know where it is, or does it have to go find out?

What Happens on Power Loss: The Homing Problem

With an incremental encoder, any power interruption — a trip, a brownout, a deliberate shut-down — erases the position count. Recovery forces a homing routine: drive the axis to a hard stop or index mark, re-establish the zero, then resume. On a single simple axis that is a few seconds. On a multi-axis machine, a gantry, or a rotary table buried inside a fixture, homing can mean unlocking guards, clearing the work zone, and a minute-plus sequence before production resumes.

Multiply that by every fault and every shift change and the "cheaper" incremental encoder starts costing cycle time and operator attention. Worse, if homing is skipped or interrupted — common under time pressure — the axis runs on a false zero and scrap or collision follows.

Multiturn Memory: Counting Turns, Not Just Angles

Single-turn absolute encoders resolve position within one revolution but lose track of how many turns the shaft made. Multiturn absolute encoders add a turns counter, so a ballscrew or rotary table knows both its angle and its cumulative revolution count after power-down.

TIMSENS time-grating angle encoders carry multiturn recording up to 65,535 turns — enough for the longest ballscrew or the most rotations a machine will see in a maintenance interval. The practical payoff: a machine can power down mid-cycle, lose mains for hours, and resume from the exact multi-turn position with no homing and no operator intervention.

Battery-Free Absolute: Why Time Grating Changes the Trade-off

Traditional absolute encoders often rely on a battery (or external capacitor) to retain multiturn counts through a power loss. That battery is a consumable: it ages, it dies, and when it does the "absolute" encoder forgets — re-introducing the very problem it was bought to solve, plus a maintenance item and a failure mode.

TIMSENS time-grating encoders are absolute by nature (0–360°) and retain position through power-down without a battery. Because position is derived from coupled traveling electromagnetic fields measured by stable time-interval electronics — not from a battery-backed counter — there is no cell to replace and no "battery-low" fault to manage. For machines in remote sites, 24/7 lines, or harsh environments where a dead encoder battery means unplanned downtime, battery-free absolute is a quiet but material reliability dividend.

Absolute Serial Interfaces Make It Useful

Absolute position only helps if the controller can read it instantly. TIMSENS time-grating encoders expose absolute data over BISS-C (0.1–5 MHz) and SSI (0.1–2 MHz) serial links, with 320 kHz internal sampling keeping the position loop tight. On power-up the drive reads the true absolute angle in the first communication cycle — no index search, no homing tab. UART and ABZ are also supported for legacy and commissioning paths, and Panasonic / open-custom links cover fixed OEM stacks.

When You Need Absolute

Specify absolute (ideally battery-free multiturn) when any of these hold:

• Safety-relevant axes — a restart must know true position before moving (prevents uncontrolled motion).
• Multi-axis / gantry systems — independent homing of each axis is slow and error-prone.
• Remote or unattended machines — no operator to run a homing routine after a power event.
• Long ballscrews / rotary tables — multiturn memory (up to 65,535 turns on TIMSENS) avoids re-zeroing deep into travel.
• High mix, frequent restart — every saved homing cycle is recovered production time.

When Incremental Still Suffices

Incremental is legitimate where the axis is always re-homed at start, or where only relative motion and speed feedback matter — simple spindles, basic conveyors, or applications with a hard index the controller visits every cycle. TIMSENS models also output ABZ up to 8 MHz for exactly these legacy and incremental interfaces. The point is not "absolute everywhere" but "absolute where a power-loss zero would cost you."

Real Specifications: TIMSENS Time-Grating Families