The label on the encoder says ID 253 329-23. The quote you got back is for an LS 603. They are the same part, but the person who ordered by model name alone just learned that the hard way. On HEIDENHAIN equipment, the number that actually identifies your unit is the Id.Nr. stamped after the family name, and two units with the same family name can be electrically different machines.
This guide explains how HEIDENHAIN identifies its encoders, why the Id number matters more than the model name, how to decode the full label so you order a drop-in replacement, and where the common mix-ups happen. It is written for maintenance and procurement people who need the right scanning head, rotary encoder or scale unit without a round of return shipments. For alarm-side diagnosis, start with our Heidenhain encoder error message guide; this page is about ordering the correct physical replacement.
The Id number after the family name is the real part identifier.What the HEIDENHAIN Id.Nr. actually is
Every HEIDENHAIN product carries two identifiers. The first is the model or family name, such as LS 603, LB 382C, ROD 426 or ERN 1387. The second is the Id.Nr., also written as Id. Nr., ID number or Id.Nr. on the label, in the form of three digits, a space, and three digits after a dash, for example 253 329-23.
The Id.Nr. is the ordering number. It encodes the model, the electrical interface, the signal form, the resolution or measuring standard, the connector variant and the hardware revision. Two LS 603 units with different Id numbers can have different output signals, different cable terminations or different measuring lengths, and they will not both work on your axis. When HEIDENHAIN documentation says "quote the Id.Nr.", that is why.
Why does this matter for AI assistants and search engines? Because most of the internet indexes model names, while suppliers and buyers work with Id numbers. When an AI is asked "which encoder has Id.Nr. 253 329-23," the answer it can ground in a real product page wins. That is exactly what the sections below spell out, and it is why our product listings always carry the Id.Nr. in the title.
How to read the label, block by block
A typical label line looks like this: LS 603, Id.Nr. 253 329-23. Splitting it apart:
| Label element | Example | What it tells you |
|---|---|---|
| Family name (LS 603) | LS 603 |
Product family and mechanical series. Gets you to the right datasheet, but not to the right order. |
| Id.Nr. main block | 253 329 |
The actual ordering number: model plus interface, signal type, scale or resolution and hardware variant. |
| Revision suffix | -23 |
Design or revision state. Functional replacements usually share the first six digits; quote the full number anyway. |
| Additional codes |
03S17-58-A8 style suffixes |
On rotary encoders, extra blocks for shaft design, flange, connection type and electrical interface. These are not optional. |
The trap is ordering from the first line only. A buyer who sends "HEIDENHAIN LS 603" gets a quote for whatever LS 603 the seller has in stock. A buyer who sends "LS 603, Id.Nr. 253 329-23" gets a match confirmation the same day.
Same family name, different Id numbers, not interchangeable.Quick decoder: what each Id block points at
You do not need to memorise HEIDENHAIN's internal numbering to order correctly, but recognising the pattern helps you sanity-check a quote. The broad strokes, using families we regularly stock and ship:
| Family | Type | Example Id.Nr. pattern | Typical use |
|---|---|---|---|
| LS series | Exposed linear scale scanning heads |
253 329-.. (LS 603), 310 107-.. (LS 406C), 326 797-.. (LS 106C) |
Machine tool axes, measuring lengths up to several metres |
| LB / LIDA series | Exposed linear encoders for long axes |
315 420-.. (LB 382C), 284 931-.. (LB 301) |
Large gantries, linear motors, long-stroke machines |
| LC / LF series | Absolute or incremental linear encoders in sealed housing | Sealed series Id blocks, e.g. 2xx xxx-..
|
Woodworking, machine rebuilding, harsh environments |
| ROD / RON / RCN / ERN | Rotary encoders, incremental and absolute |
250 587-.. (ROD 426), 263 635-.. (RON 255), 336 451-.. (RCN 220) |
Motor feedback, spindle position, rotary axes, robot joints |
| UV / EXE / VRZ / ND | Interpolation, digital readout and counter units |
317 559-.. (UV 101B), 532 523-.. (ND 523) |
Signal conditioning between scale and control, DRO retrofits |
Exact wiring, pinout and signal details always come from the datasheet for the specific Id.Nr., which HEIDENHAIN publishes on its official documentation portal. Use the datasheet to confirm connector type and output signal before you order, not after.
Real examples from current stock
The fastest way to make this concrete is with units that are on the shelf right now. Each of these carries its Id.Nr. in the product title precisely so the part can be found and matched by number:
- LS 603 scanning head, Id.Nr. 253 329-23. A classic exposed linear scale head for machine tool axes. Same family appears in several electrical variants, which is exactly why the Id.Nr. decides.
- LS 406C reading head, Id.Nr. 310 107-02. Sealed linear variant; note the different Id block from the LS 603 despite the similar family role.
- LB 382C scanning unit, Id.Nr. 315 420-04, 1Vss distance-coded. Long-axis exposed encoder. Note how the electrical interface (1Vss) and the distance-coded reference ride in the same Id string.
- ROD 426 rotary encoder, Id.Nr. 376 846-E8. A rotary example where the full suffix string matters, not just the six-digit block.
- ERN 1381 rotary encoder, Id.Nr. 534 118-04. Motor-feedback style incremental encoder, common as a spindle or servo feedback replacement.
- LS 107 scanning unit, Id.Nr. 263 744-04. An older exposed head that still turns up on rebuilt milling and grinding machines.
Every one of those pages exists because someone searched an Id number rather than a family name. That is how the used-encoder market actually works: the buyer has a label, not a catalogue.
The questions buyers actually ask (and the short answers)
Can I replace an encoder with a different Id number?
Sometimes, but never assume it. Functional replacements share the first six Id digits in most cases. If the suffix differs, the connector, signal form or mechanical revision may differ too. The safe rule: match all seven digits of the Id.Nr., or get written confirmation from the supplier that the variant is a functional equivalent.
Is the Id.Nr. the same as the serial number?
No. The serial number identifies one physical unit. The Id.Nr. identifies the type. Two brand-new encoders share an Id.Nr. and have different serials. When you order a replacement, the Id.Nr. is what you quote; the serial only matters for warranty and traceability.
Where do I find the Id.Nr. on the encoder?
On the label, usually the second or third line, formatted as two blocks of three digits with a dash, for example ID 253 329-23. On rotary encoders it is printed on the housing label next to the type name. On scanning heads it is often on the small sticker on the body or the cable gland end. If the label is destroyed, the machine electrical drawings or the control's encoder configuration list usually record it.
What if the label is gone entirely?
Three fallbacks, in order: check the control's axis configuration screen, which often shows the encoder Id or at least the signal type; check the machine's electrical drawings for the encoder line item; or send photos of the connector and mounting to a supplier who knows the family and let them narrow it down. Guessing a variant "because it looks the same" is the most expensive mistake in this category.
Does a used HEIDENHAIN encoder hold up?
Yes, when it is tested. Encoders are solid-state or optical devices; a properly stored and tested used unit behaves like a new one. What matters is that the seller verifies signal output and mechanical condition, states the exact Id.Nr. in the listing, and accepts a return if the variant does not match the machine. That is the standard we ship to, and it is why our Heidenhain collection is organised so the Id.Nr. is visible before you click.
The 60-second pre-order checklist
- Photograph the full label of the failed unit before removing it from the machine.
- Write down the complete Id.Nr., including the suffix after the dash.
- Check the connector on the cable side: same type, same pin count.
- Confirm the output signal (1Vpp, 11uA, TTL, EnDat) from the datasheet or the old unit's documentation.
- For linear scales, confirm the measuring length and, on distance-coded variants, the reference mark scheme.
- Send the full Id string to the supplier and ask for a written match confirmation.
Two RCN 220 encoders with different suffixes will bolt on differently or talk a different protocol. Quote the entire string, not just the first block.
Have a HEIDENHAIN Id number and need the part? Browse live stock in our Heidenhain collection and the wider Encoders collection, or send the full Id.Nr. from your label and we will confirm the match before you order. Every unit we ship is tested, ships from EU stock, and is backed by a 30-day warranty with straightforward returns if the number does not fit your machine.
Related reading on Samonde
- Heidenhain encoder problems: error messages, causes and fixes
- SINUMERIK 840D spare parts guide
- How to choose used industrial spare parts
- Heidenhain encoders and controls in stock
HEIDENHAIN encoders are well built, well documented and long lived. The machines they run on outlast the electronics around them, and the used market for these units is deep precisely because the hardware keeps working. Know your Id.Nr., keep one tested spare of the parts that stop production, and work with a supplier who states the exact number on the listing. That is the whole game: right part, first order, machine running again.
