Leuze / Photoelectric sensors

A Leuze PRK gives you light switching and dark switching at the same time, on two different pins. You do not order a different sensor for the opposite behaviour, you wire to the other pin.

PRK, HT and LS photoelectric sensors are on conveyors and packaging lines across New Zealand. The numbering reads cleanly once the suffixes make sense.

Both outputs are already there

The most useful thing on this page, and most people do not know it.

A PRK25C carries two digital switching outputs:

Both are PNP transistor outputs and both are live.

What that means practically

If a machine needs the opposite behaviour, move the wire from pin 4 to pin 2. No new sensor, no reconfiguration.

And if a replacement sensor appears to work backwards, check which pin the harness lands on. That is a two minute check that saves ordering a part you already have.

This is a real difference from brands where light and dark switching are separate part numbers. Compare the SICK and Schneider ranges covered on our SICK photoelectric and OsiSense pages, where the switching mode is in the order code.

Reading a Leuze sensor number

Take PRK25C.D/4P-M12.

The family prefix

LS and LE are two separate part numbers. A knocked bracket at one end is a single part order, so tell us which half.

The output group

The letter is the transistor type and the digit relates to the pin assignment.

A PNP sensor in a circuit expecting NPN will not switch the load. Same sensor otherwise, and the difference is two characters.

The variant suffix is where the useful detail sits

Three PRK25C variants, and each exists for a specific problem.

The .D is for clear film

Leuze states the application plainly: detection of stretch-wrapped objects.

Stretch wrap is the hardest thing a retro-reflective sensor has to deal with. It is clear, it is shiny, it flaps, and it reflects light back in ways that look like the reflector.

So if a palletiser sensor keeps missing wrapped pallets, a .D variant is the answer, not another standard sensor or a sensitivity adjustment.

The trade is range: 8 m rather than 10 m.

The .A removes the minimum distance

Autocollimation puts the transmitter and receiver optics on the same axis.

A standard retro-reflective sensor has a blind zone close to the lens, because the two optics sit side by side and a very close target falls outside the receiver's view.

So if you need to detect something very close to the sensor face, that is the variant to ask for. A standard sensor mounted too close simply will not see the target.

Again the trade is range: 5 m rather than 10 m.

The .D1 adds a potentiometer

A 270 degree potentiometer for sensitivity adjustment. The plain .D has no adjustment.

On a marginal or dusty application that adjustment is the difference between a sensor that works and one that needs replacing with a different variant. Worth having on anything awkward.

Operating range and operating range limit

Two numbers on every Leuze datasheet, and only one of them is a design figure.

Leuze defines the limit in exactly those words.

Design to the operating range, not the limit. A sensor working at its limit has no margin for a dusty lens, a dirty reflector or a slightly misaligned bracket.

So a sensor installed at 11 m on a 10 m rating will work on commissioning day and start failing when the plant gets dirty. That is a common and confusing fault, and it is a design issue rather than a sensor issue.

Both figures are quoted against the TK(S) 100x100 reflector. A smaller reflector gives a shorter range.

The reflector is a separate part

And it matters more than people expect.

Leuze quotes ranges against the TK(S) 100x100 reflector, which is the reference.

If a sensor is replaced but the reflector is not, the reflector is still the likely fault. Clean it first; replace it if the surface has gone milky.

On a replacement where the reflector is sound and in place, you do not need another. On a new installation you do.

The 25B to 25C migration

Directly useful, because a lot of New Zealand plant runs the older 25B series.

The old numbering used a /66 scheme that reads nothing like the current one. Leuze publishes the replacements.

Notice that the .3 in the old number becomes .D, and .31 becomes .D1. The variant survived the renumbering even though the code did not.

So if you have a 25B number, we can map it. Send it and we will quote both a used original and the current equivalent.

The connection suffix

The number before the connector is the pigtail length in millimetres.

A pigtail version exists for a reason. Where a sensor sits in a tight bracket, a rigid connector on the body cannot be reached, and a short flying lead solves it.

So a body-connector version is not a drop-in for a pigtail version in a confined mounting. Check the existing one.

Cable material is PUR, which suits drag chains and oil better than PVC.

Common specifications

IP69K is the washdown rating

Worth flagging for New Zealand meat and dairy.

IP69K covers high pressure and high temperature cleaning, which is a considerably harder test than IP67 alone.

So a PRK25C survives a washdown that would kill a lesser sensor. If a plant has been replacing sensors regularly in a wet area, the rating is worth checking.

A red LED is visible

You can see where the beam is pointing, which makes alignment far easier than an infrared sensor.

On a retro-reflective installation, look for the red spot on the reflector. If it is off-centre, that is the fault.

An AS-i note

Worth knowing if a plant runs AS-Interface.

Leuze notes on certain variants that pin 2 is unassigned, hence especially suitable for connection to AS-interface I/O coupling modules.

So an AS-i friendly variant deliberately leaves pin 2 free, where a standard variant uses it for the second switching output.

If a sensor is going onto an AS-i coupler, that distinction matters.

Which principle fails how

Worth checking before ordering, because a good proportion of replaced sensors were working.

Background suppression is the answer to the colour problem

A diffuse sensor that works on white product and misses black product is not faulty. It judges reflected quantity, and a dark matt object reflects far less.

An HRT judges distance instead, ignoring anything beyond a set point, which makes it far less sensitive to target colour.

So the fix is an HRT, not another HT.

Polarised is the answer to the shiny problem

A polished or wrapped target can reflect enough light to look like the reflector, so a plain retro-reflective sensor stays made when it should break.

The P in PRK is polarised, which filters that out. The .D variant goes further for stretch wrap specifically.

What to send us

The full type code and the 8-digit order number.

PNP or NPN, if the label has faded.

Which half, on a through-beam LS and LE pair.

Whether you need the reflector.

The connection. Body connector or pigtail, M8 or M12.

An old 25B number is fine. We can map it to the current equivalent.

Before ordering a replacement

What we can supply

Current production. The PRK, HT, HRT, LS, LE and ET ranges across series and output types, plus TK reflectors, brackets, cordsets and mounting hardware. Quoted with a delivered lead time.

Discontinued. The 25B and earlier series. Surplus and tested used, or mapped to the current equivalent, whichever suits you.

Reflectors and brackets separately. Often the cheaper fix.

Bulk. Photoelectric sensors are a machine consumable. Send us the schedule.

We buy Leuze sensors

Working sensors from a decommissioned line are worth having, particularly older 25B units that plants still run. See Sell To Us.

Related

Leuze overview, MLC light curtains and RSL laser scanners.

For photoelectric sensors from other brands see SICK W series, Omron E3Z and Schneider OsiSense.

Send us your part numbers

And if a replacement seems to work backwards, check whether the harness is on pin 4 or pin 2 before ordering anything. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Leuze electronic. Leuze and Leuze electronic are trademarks of Leuze electronic GmbH + Co. KG. AS-Interface is a trademark of AS-International Association. All trademarks, brand names and part numbers are the property of their respective owners and are used here for identification purposes only.