FS-S72 Color Mark Sensor
The registration trigger for packaging print: every cut, seal and bag-forming stroke lands on the eyemark — at full line speed.
- 200 μs or faster response — ~1 mm scatter at 300 m/min
- 18–28 mm sensing window absorbs web flutter
- Mark (contrast) mode + taught-color match mode
- FS-S72 NPN / FS-S72P PNP — one family, both PLC styles
- 24 VDC open-collector, wired straight to the PLC input
Why Registration Lines Live and Die by the Mark Sensor
On a bag-making or form-fill-seal machine, the printed registration mark (eyemark) is the only truth the machine has about where the artwork actually is. Film stretches, splices pass, tension drifts — and if the mark trigger arrives late or scattered, the logo gets guillotined and a whole roll becomes scrap. The FS-S72 exists for exactly this job: it reads the contrast step between mark and background and fires its output in 200 μs or less, so the correction loop is fed with a signal whose own jitter is measured in fractions of a millimeter, not multiples.
Setup is deliberately forgiving. The sensor works anywhere inside an 18–28 mm window from the web, so it tolerates flutter and bracket tolerance instead of demanding a single exact gap. Two operating modes share the same housing: classic mark (contrast) detection for registration, and a color-match mode that switches ON only when the sensed color equals a taught reference — a free film-variant check on hardware you already mounted. Order FS-S72 for NPN systems or FS-S72P for PNP; everything else is identical.
Mark Detection & Trigger Timing
Each eyemark crossing the beam produces an output edge the PLC uses to time the cut or seal. The shorter the sensor response, the tighter the print-to-cut registration at speed.
Technical Specifications
| Model | FS-S72 (NPN) / FS-S72P (PNP) |
|---|---|
| Output type | Open-collector; ON on mark detection (mark mode) / ON on color match (color mode) |
| Sensing distance | 18–28 mm |
| Response time | 200 μs or less |
| Operating modes | Mark (contrast) detection / taught-color match |
| Operating voltage | 24 VDC |
| IP rating / dimensions / accuracy | Contact factory for latest datasheet (not yet published) |
Model Selection
| Model | Output | Choose when… |
|---|---|---|
| FS-S72 | NPN open-collector | PLC uses sinking inputs (common on Japanese-style controls) |
| FS-S72P | PNP open-collector | PLC uses sourcing inputs (common on European/US controls) |
The FS-S72 is a detection sensor, not an IEC 61496 certified safety component, and must not be used on its own for personnel protection.
Registration Duties It Covers
Bag-Making Machines
Synchronize bag forming, cutting and sealing to the printed mark so artwork lands centered on every bag.
Form-Fill-Seal Lines
Feed the registration correction loop on VFFS/HFFS machines running printed film at high web speed.
Labeling Machines
Detect the print mark near the label gap to dispense each label at the correct position.
Converting & Slitting
Pick up register marks to align print stations and trigger slit/cut positions on converting lines.
Frequently Asked Questions
How much registration error does sensor response time actually cause?
At 300 m/min the web moves 5 mm every millisecond. A sensor that responds in 1 ms therefore adds up to 5 mm of positional scatter before the machine even reacts; the FS-S72's 200 μs (or faster) response holds the sensor's own contribution to about 1 mm at that speed, which is why it suits high-speed bag-making and form-fill-seal registration.
What is the correct mounting distance?
Anywhere inside the 18–28 mm sensing window. Because it is a 10 mm working band rather than a single fixed point, normal web flutter and bracket tolerance do not force constant re-adjustment.
FS-S72 or FS-S72P — which do I need?
They differ only in output transistor: FS-S72 is NPN open-collector for sinking PLC inputs, FS-S72P is PNP open-collector for sourcing inputs. Sensing range, response and 24 VDC supply are identical, so machine builders shipping to both NPN and PNP markets can standardize on one sensor family.
Can it do more than find the eyemark?
Yes. Besides mark (contrast) mode, a color mode switches the output ON only when the sensed color matches a taught reference — usable as a basic color-consistency check on the same hardware, for example confirming the correct film variant is loaded.
Is FS-S72 the same as the "FS-72" seen on some listings?
No — the correct model designation for this product is FS-S72 (NPN) / FS-S72P (PNP). Differently specified "FS-72" listings elsewhere have not been confirmed as the same product, and we do not attribute their figures to the FS-S72.
What about IP rating, housing size and detection accuracy?
These figures are not yet published for this model — contact the factory for the latest datasheet rather than relying on unconfirmed third-party numbers. A 3D STEP model is available on request for machine-design integration.
Can I get samples, and what are the export terms?
Sample units for line trials are available — contact the factory with your machine type (bag maker, labeler, FFS, slitter) and PLC input polarity. Quotation, lead time and certification documents are provided on request. Note the FS-S72 is a detection sensor, not an IEC 61496 certified safety component.
Specs reviewed by Engineer Cai, Senior Application Engineer. See certificates.
Safety Light Curtain — Customer Cases
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