Category: Buying Guides

An inductive sensor stops at the first piece of metal. A photoelectric sensor stops at the first opaque object. A magnetic proximity switch does neither — it responds to a magnetic field, and a magnetic field passes straight through stainless steel, aluminium, plastic, glass and brass as though they were not there.

That single property solves a class of sealing problem that nothing else addresses cleanly, and it is why magnetic switches survive in positions where other technologies are replaced every few months.

What that actually buys you

The sensor goes outside. The magnet goes inside. Nothing penetrates the wall.

Consider a pneumatic cylinder. The piston position needs to be known. An inductive sensor cannot see through the aluminium barrel. A magnetic switch mounted on the outside detects the magnet in the piston with no penetration, no seal and no wetted part. The same logic applies to a stainless steel vessel with a float inside, to a sealed gearbox, and to any hygienic enclosure where a fitting would create a cleaning problem.

There is a second benefit that matters in dirty plant: because the sensor does not need line of sight and does not care about the material between it and the magnet, dust, product build-up, paint and condensation are all irrelevant. A magnetic switch behind a layer of cement dust works exactly as well as a clean one.

The D33C range

Our magnetic proximity switches come in M12, M18 and M30 bodies, NPN three-wire, 30 mA, short-circuit protected:

• D33C-12MD-NM-3S — M12
• D33C-18MD-NM-3S — M18
• D33C-30MD-NM-3S — M30

Plus speed and direction variants, carrying an SD suffix:

• D33C-18MD-NM-3S-SD — M18 with speed and direction
• D33C-30MD-NM-3S-SD — M30 with speed and direction

The output rating is the thing to watch

This range is rated 30 mA, not the 200 to 300 mA of the D30C inductive or capacitive ranges. It is designed to feed a controller input.

Connecting one directly to a contactor coil or a relay is the single most common misapplication of this series. It will either fail immediately or, less helpfully, work for a while and then fail. If the signal must switch a load, route it through a PLC output or an interposing relay driven by something rated for it.

Speed and direction in one sensor

Detecting rotation direction requires two signals in quadrature. Traditionally that meant two sensors, mechanically aligned to a precise offset — and holding that alignment in an industrial environment, through vibration and maintenance, is genuinely difficult.

The SD variants provide both channels in a single housing, with the offset fixed at manufacture. One sensor, one mounting, no alignment to lose. For reversible conveyors, hoists, and any drive where reverse rotation is a fault condition, this is the more robust engineering answer.

Our guide to speed and underspeed monitoring covers the target geometry and controller requirements.

Where magnetic switches earn their place

• Pneumatic and hydraulic cylinder position — piston magnet detected through the barrel
• Level switching in stainless or plastic vessels — magnetic float inside, sensor outside, nothing wetted
• Hygienic applications — no penetration means no crevice and no cleaning problem
• Door, hatch and guard position — magnet on the moving part, sensor on the frame, tolerant of alignment
• Rotation and speed monitoring in wet or dusty plant where optical sensing fails
• Explosion-hazard adjacent areas where keeping electronics outside the enclosure is preferable
• Through-wall sensing generally, wherever drilling is undesirable

The constraints, honestly

You need a magnet on the target. Where one is already present — a cylinder piston, a magnetic float — this is free. Where it is not, you are adding a component, and it must be fixed securely enough to survive the application.

Ferrous material between sensor and magnet blocks it. The technology passes through non-ferrous walls. A steel wall will shunt the field. Check the wall material before designing around this.

Stray magnetic fields interfere. Near large motors, welding equipment or magnetic separators, consider whether the environment is magnetically clean.

Magnet strength and orientation matter. Sensing distance depends on the magnet, not only the sensor, and magnets have polarity. A magnet fitted the wrong way round will not be detected, which produces a puzzling commissioning fault.

Choosing between magnetic and inductive

Magnetic when you need to sense through a non-ferrous wall, when the environment is wet or dirty enough to defeat other technologies, when a magnet is already present on the target, or when you need direction as well as speed.

Inductive when the target is already ferrous metal and directly accessible, when you need higher output current to drive a load, or when adding a magnet is impractical. It is also cheaper.

Specifying

Tell us the wall material and thickness the sensor has to see through, whether a magnet is already present and if so its type and orientation, the required sensing distance, whether direction sensing is needed, and what the output feeds. For cylinder applications, the cylinder make and bore usually identifies the magnet arrangement.

A sensor fails. The label says something from a European or Japanese manufacturer, the lead time is eight weeks, and someone suggests finding an Indian equivalent. That is usually a good idea. It goes wrong when the cross-reference is done on body size and sensing distance alone.

Those two parameters determine whether the part fits. Four more determine whether it works, and two others determine whether it keeps working. Here is the full list.

The parameters that must match

1. Body size and thread

M8, M12, M18, M30, M36, M50. Straightforward, but check thread length as well as diameter — a sensor with a shorter barrel may not reach through a thick bracket, and one with a longer barrel may bottom out.

2. Sensing distance, adjusted for the target

Match the nominal figure, then check what the target actually is. Catalogue sensing distances are quoted against standard mild steel. If the machine senses aluminium or stainless steel, the effective distance is shorter — and if the original sensor was specified with that already accounted for, a nominal match may not be a functional one.

Our note on reduction factors for different metals has the correction figures.

3. Shielded or unshielded

This is the one most often missed, and it fails in a specific and confusing way. A shielded sensor can be mounted flush in metal. An unshielded one senses further but needs a clear zone around the face.

Fit an unshielded sensor into a mounting designed for a shielded one and it triggers on the bracket, permanently. The symptom is a sensor that reads on with nothing in front of it, and it gets diagnosed as a faulty sensor about half the time. See shielded versus unshielded.

4. Output type — NPN or PNP

Must match the input card. A PNP sensor into an NPN input does nothing at all, which at least is obvious. The subtler failure is an input card that accepts both but was configured for one.

5. Contact function — NO or NC

Match the original unless you are deliberately changing the logic. Substituting NO for NC and fixing it in the PLC works, but it leaves a machine whose wiring no longer matches its drawings, and the next person will lose a morning to it.

6. Supply voltage and output current

Confirm the supply range covers what the panel provides, and that the output current rating exceeds what the load actually draws including inrush.

The two that get forgotten

Connection method

Cable or connector. If connector, which one — M12 four-pin is common but not universal, and pin assignment varies. If cable, what length? A replacement with a 2 metre tail where the original had 5 metres means a junction box that was not in the plan.

This is worth specifying rather than accepting, because a made-to-length cable is usually available and removes the problem entirely.

Switching frequency

Rarely checked, occasionally decisive. If the sensor is counting teeth on a rotating shaft or detecting parts on a fast line, the replacement must switch at least as fast as the original. A sensor that is perfectly adequate for a limit position will miss counts on a high-speed application.

If the application is counting or speed sensing, say so — it changes the recommendation, often towards the D33C range.

What to send us

The fastest cross-reference comes from three things:

1. The full part number from the label, photographed rather than transcribed. Sensor labels use characters that are easy to misread, and a wrong digit sends the whole exercise sideways.
2. A photograph of the sensor installed, showing the mounting and how close the surrounding metal is. This answers the shielded question, the thread length question and often the target question at once.
3. What it is sensing, and at what distance.

If you have the machine wiring diagram, the page showing the sensor is more useful than the sensor datasheet.

What you get from switching

Replacing imported sensors with domestically manufactured equivalents changes three things that matter on a maintained asset.

Lead time becomes a production question. No ocean freight, no customs clearance in the critical path.

The part stays available. Imported ranges get rationalised, and distributors change. A part made in Mumbai is subject to neither.

Variants become possible. Cable length, connector type and housing details can be specified rather than accepted — which, on a machine where you are replacing a dozen sensors anyway, is a chance to remove the junction boxes that were only ever there because the standard cable was too short.

Where we would tell you not to switch

If the original is doing something an inductive, capacitive, photoelectric or magnetic switch cannot do — absolute linear or rotary position measurement, for example — then a proximity switch is not the equivalent, whatever the mounting suggests. In that case the right answer is a position transducer from the Novotechnik range, and we will say so rather than sell you the wrong category of device.

Every Accent sensor part number describes the complete specification of the product. Series, body size, sensing distance, output type, contact function, wiring and protection are all in there. Once the pattern is clear, you can read any part number off a label and write a replacement code without opening a catalogue.

This page is the decoder for the whole range.

The series prefix

The first four characters identify the technology:

• D30C — DC inductive proximity switch, three-wire. The general-purpose range.
• D31C — photoelectric switch.
• D32C — capacitive proximity switch.
• D33C — magnetic proximity switch, including speed and direction variants.
• D20C — NAMUR inductive proximity switch, for intrinsically safe duty.
• A20C — AC two-wire inductive proximity switch.

Inductive, capacitive and NAMUR: D30C, D32C, D20C, A20C

These follow a common pattern:

D30C-1204-NM-3S

D30C	Series
12	Body thread in mm — 08, 12, 18, 30, 36 or 50
04	Nominal sensing distance in mm
N	Output transistor — N for NPN, P for PNP
M	Contact function — M for normally open (make), B for normally closed (break)
3S	Three-wire, short-circuit protected. Plain 3 omits the protection.

So the body and sensing distance pair together as four digits. 1204 is M12 with 4 mm sensing. 5030 is M50 with 30 mm. 3015 is M30 with 15 mm.

A20C differs only in the output section, because an AC two-wire sensor has no transistor type. A20C-1808-M-2 is M18, 8 mm, normally open, two-wire.

D20C NAMUR parts carry the NA suffix instead of an output code, because a NAMUR sensor does not switch a load — it changes the current it draws. D20C-1805-NA is M18 with 5 mm sensing, NAMUR output.

Photoelectric: D31C

Photoelectric parts need two extra fields, because sensing mode and range are independent of body size.

D31C-18TB-15000-PL-2S

D31C	Series
18	Body thread — 18 or 30
TB	Sensing mode — TB through-beam, RR retro-reflective, DR diffuse reflective
15000	Sensing range in mm
P	Output — P for PNP, N for NPN
L	Logic — L for light-on, D for dark-on
2S	Short-circuit protected

Magnetic and speed sensing: D33C

D33C-18MD-NM-3S is an M18 magnetic proximity switch, NPN normally open, three-wire, short-circuit protected, rated 30 mA.

An additional SD suffix indicates the speed and direction variant, used for rotation monitoring where the control system needs to know not just that a shaft is turning but which way. D33C-30MD-NM-3S-SD is the M30 version.

Note the output current: the D33C range is rated 30 mA rather than the 200 to 300 mA of the switching ranges. It is designed to feed a controller input, not to drive a contactor directly. Driving a relay coil from one is a common and avoidable mistake.

Output current by series

• D30C — 200 mA and 300 mA depending on variant
• D31C — 200 mA
• D32C — 300 mA
• D33C — 30 mA
• A20C — 200 mA

Check the actual current your load draws. A contactor coil inrush can be several times its holding current, and a sensor sized on the holding figure will fail.

The suffixes that matter most

S for short-circuit protection. The difference between -3 and -3S. Small price difference, prevents the most common field failure. Specify it unless there is a reason not to.

M and B. Make and break — normally open and normally closed. Worth choosing deliberately rather than defaulting: on a safety-relevant interlock, normally closed means a cut cable produces the stopped state.

N and P. NPN and PNP. Determined by your input card, not preference. See PNP versus NPN sensors.

Reading a worn label

If the label on an installed sensor is partly illegible, you can usually reconstruct the code. Measure the thread to get the body size. Count the wires: two means A20C or D20C, three means one of the DC ranges. Trace the output to see whether it sources or sinks. Then send us what you have — a photograph of the sensor in place and its wiring is generally enough for us to identify the part.

Cross-referencing another manufacturer

If you are replacing a competitor part rather than an Accent one, send us the full part number from the label and the application. We will identify the equivalent rather than ask you to work through the decoder — see our guide to replacing imported proximity switches.

A great deal of working plant in India was built around AC contactor logic. There is no 24 V DC rail, no PLC input card, and no convenient place to get one — just a contactor coil that needs switching and a mechanical limit switch that has finally worn out.

Replacing that limit switch with a modern DC three-wire proximity sensor means adding a power supply, finding panel space, and running a new circuit. The A20C exists so you do not have to.

What a two-wire AC sensor is

It wires exactly like a mechanical switch: in series with the load, two wires, no separate supply. The sensor takes its operating power through the load itself. When it switches, current flows to the contactor coil; when it does not, only a small residual current flows.

That makes it a genuine drop-in replacement for a limit switch, a reed switch or a microswitch, with no panel modification at all. For retrofit work on ageing plant this is frequently the difference between a half-hour job and a rewiring project.

The A20C range

Eight body and sensing combinations, each available normally open or normally closed:

• M12 — 2 mm and 4 mm sensing
• M18 — 5 mm and 8 mm
• M30 — 10 mm and 15 mm
• M36 — 20 mm
• M50 — 30 mm

All are two-wire, rated 200 mA. The ordering code follows the house pattern:

A20C-1808-M-2 — M18 body, 8 mm sensing, normally open (M for make), two-wire. Substitute B for break to get the normally closed version.

The two things that catch people out

Two-wire AC sensors have two well-known characteristics. Neither is a fault, but both cause confusion when they are not expected.

Residual current. Because the sensor powers itself through the load, a small current flows even when the sensor is off. In most cases the contactor coil ignores it. With a very low-burden load — a solid-state relay input, an electronic timer, some PLC AC input cards — that residual current can be enough to hold the load partially on, or to make an input read permanently true.

The symptom is a contactor that hums, or an input that never clears. The fix is a bleeder resistor across the load to give the residual current somewhere to go. Check the minimum load current your device requires before ordering.

Voltage drop. The sensor drops a small voltage across itself when conducting, because it needs that to operate. With a single sensor this is immaterial. Put three in series for an interlock chain and the drops add, and the coil at the end may not see enough voltage to pull in reliably.

If you are chaining sensors, add up the drops and compare against the coil pull-in voltage. Where the sum is marginal, use DC sensors and a relay instead. Our note on series and parallel connection of proximity switches covers the arithmetic.

When to use AC two-wire, and when not to

Use it for direct replacement of a worn mechanical switch in an AC panel, where the load is a contactor or solenoid with a normal burden, and where you want to avoid adding a DC supply.

Do not use it where the load is electronic and low-burden, where several sensors must be chained in series, where fast switching is required, or where you are building new. On a new machine, specify DC three-wire from the D30C range — more output options, no residual current, no voltage drop, and better diagnostics.

Why this range still matters

Because a very large amount of Indian manufacturing capacity was installed before DC control became standard, and that plant still has to run. A machine from the 1990s with a failed limit switch does not need a control system upgrade. It needs a sensor that fits the wiring that is already there.

The A20C is made in Mumbai to IEC 60947-5-2, so obsolescence is not a concern in the way it is with an imported range that may be rationalised away.

Ordering

Send the body size the existing mounting takes, the sensing distance needed, whether the function is normally open or normally closed, the AC supply voltage, and what the sensor is switching — ideally with the coil rating. If you are replacing a mechanical switch, a photograph of the installation usually answers the mounting questions faster than measurements do.

When the sensing distance you need is beyond what an inductive switch can reach, or the target is not metal, the answer is usually photoelectric. The D31C range covers that requirement with 72 variants in M18 and M30 bodies, and the single most important decision is not the model number — it is which of the three sensing modes you choose.

Get the mode right and a photoelectric sensor runs for years. Get it wrong and it becomes the device the maintenance team resents.

The three sensing modes

Through-beam puts the emitter and the receiver in separate housings, facing each other. The target is detected when it breaks the beam. This is the most reliable mode by a wide margin: the receiver sees a strong, direct signal, so dust, fog, mist and a dirty lens all have to degrade it a long way before detection fails. It is also the only mode that reliably detects shiny, dark, transparent and irregularly shaped objects, because it does not depend on anything being reflected back.

The cost is installation. Two housings, two mounting brackets, and cable to both sides.

Retro-reflective puts the emitter and receiver in one housing and a reflector opposite. The beam travels out, bounces off the reflector and returns. Detection occurs when the target interrupts it. You get most of the range of a through-beam arrangement with only one electrical connection to make — the reflector needs mounting but not wiring.

The limitation is shiny targets. A polished or reflective object can bounce enough light back to look like the reflector, and the sensor misses it.

Diffuse reflective puts everything in one housing with no reflector at all. The beam reflects off the target itself. Simplest to install, shortest range, and most sensitive to the target surface — a matt black object reflects very little and is detected at a fraction of the distance a white one is. Background objects within range can also trigger it.

The D31C range

Diffuse reflective

• M18 — 100 mm and 300 mm
• M30 — 500 mm, 1000 mm, 2500 mm and 3000 mm

Retro-reflective

• M18 — 1000 mm, 2000 mm, 3000 mm and 5000 mm
• M30 — 10000 mm, 15000 mm and 20000 mm

Through-beam

• M18 — 1000 mm, 3000 mm, 5000 mm, 10000 mm and 15000 mm

Every variant is available in all four output combinations, three-wire, 200 mA, short-circuit protected.

Reading the ordering code

A typical part number:

D31C-18TB-15000-PL-2S

• D31C — photoelectric switch series
• 18 — M18 body (or 30 for M30)
• TB — sensing mode: TB through-beam, RR retro-reflective, DR diffuse reflective
• 15000 — sensing range in millimetres
• P — output type: P for PNP, N for NPN
• L — output logic: L for light-on, D for dark-on
• 2S — short-circuit protected

So D31C-30RR-20000-ND-2S is an M30 retro-reflective unit with 20 metre range, NPN output, dark-on, short-circuit protected.

Light-on or dark-on

This catches people out because the intuitive answer is often the wrong one.

Light-on switches the output when the receiver sees light. Dark-on switches when it does not.

For a through-beam or retro-reflective sensor detecting an object passing through the beam, dark-on gives you an output when the object is present — which is usually what the control logic wants. For a diffuse sensor, light-on gives you an output when the object is present, because the object is what returns the light.

There is also a fail-safe consideration. With through-beam set to dark-on, a failed emitter, a cut cable or a power loss all produce the same state as object present. If that state stops the machine, the failure is safe. If it starts something, it is not. Think this through for the specific function rather than accepting the default.

Choosing the mode for your application

• Transparent objects — through-beam, with sensitivity adjusted. Glass and clear film are close to invisible to diffuse sensors.
• Shiny or polished metal — through-beam. Retro-reflective will miss it.
• Dark or matt targets — through-beam or retro-reflective. Diffuse ranges collapse on dark surfaces.
• Dusty environments — through-beam, and specify more range than the geometry needs so there is margin as the lenses foul.
• Long distances — retro-reflective in M30 reaches 20 metres, the longest in the range.
• Limited access on one side — retro-reflective or diffuse, since only one side needs wiring.
• Short-range presence detection with easy access — diffuse, the simplest and cheapest to install.

Specifying with margin

The quoted range is measured under clean conditions with a standard target. In a working plant, lenses accumulate dust and reflectors get knocked. Specify a sensor whose rated range comfortably exceeds the actual distance, so there is headroom to lose before detection becomes marginal.

A 3 metre gap served by a 3 metre sensor will work at commissioning and become intermittent by the second monsoon. A 5 metre sensor on the same gap will not.

Ordering

Send us the distance, the target — material, colour, surface finish, size, whether it is transparent — the environment, whether both sides of the gap are accessible, and the output your controller expects. We will specify the mode and return the part number. Our photoelectric switch range is manufactured in Mumbai, and non-standard cable lengths are available on request.

If the distance is short and the target is metal, an inductive switch from the D30C range will usually be cheaper and more robust — worth checking before defaulting to photoelectric.

The D30C is the range most Indian plants actually run on: a DC three-wire inductive proximity switch, made in Mumbai to IEC 60947-5-2, in every combination of body size, sensing distance and output that ordinary machine building needs.

There are 72 variants. That sounds like a lot until you understand the ordering code, at which point specifying the exact part you need becomes a single line. This guide explains the code and the four decisions behind it.

Reading the ordering code

A typical part number looks like this:

D30C-1204-NM-3S

It decodes as:

• D30C — the series: DC inductive proximity switch
• 12 — body thread, M12
• 04 — nominal sensing distance, 4 mm
• N — output transistor type: N for NPN, P for PNP
• M — contact function: M for normally open (make), B for normally closed (break)
• 3S — three-wire with short-circuit protection. Plain 3 is the same without protection.

So D30C-5030-PB-3S is an M50 body, 30 mm sensing, PNP, normally closed, three-wire, short-circuit protected. Once the pattern is clear you can write the part number straight onto a requisition.

Decision one: body size and sensing distance

These two are linked. A larger coil senses further, so body size and sensing distance move together across the range:

• M8 — for tight mechanical spaces, shortest sensing distance
• M12, 4 mm — the general-purpose small sensor
• M18, 5 mm and 8 mm — the most widely used size in Indian plants
• M30, 10 mm and 15 mm — where standoff matters or the target position is less well controlled
• M36, 20 mm — heavy machinery, larger clearances
• M50, 30 mm — maximum inductive sensing distance in the range

Two cautions on sensing distance. First, the quoted figure is the nominal distance against a standard mild steel target; the assured operating distance you should design to is shorter. Leave margin. Second, non-ferrous targets reduce the distance — stainless steel, aluminium, brass and copper each by a different factor. Our note on reduction factors for different metals gives the arithmetic. Specifying an M12 4 mm sensor for an aluminium target at 3.5 mm is a fault waiting to happen.

Decision two: NPN or PNP

This is determined by your input card, not by preference. PNP sources current into the input and is the general standard in Europe and increasingly in India. NPN sinks current and is common in Japanese and some Indian-built equipment.

Get it wrong and the sensor appears dead, or appears permanently on. If you are replacing an existing sensor, match what is already there unless you are also changing the input card. Our guide to PNP versus NPN explains how to tell which you have.

Decision three: normally open or normally closed

Normally open (M) is the default: the output switches on when a target is present. Normally closed (B) switches off when a target is present.

The reason to choose NC deliberately is fail-safe behaviour. On a guard interlock or an end-of-travel limit, a normally closed sensor means a broken cable produces the same signal as an unsafe condition, so the machine stops. With normally open, a broken cable looks identical to a healthy sensor with no target, and the machine keeps running. Where the consequence of a missed detection is significant, specify NC.

Decision four: short-circuit protection

The 3S variants include short-circuit protection on the output; the 3 variants do not. The price difference is small and the failure it prevents is common — a crushed cable or a wiring error that shorts the output destroys an unprotected sensor immediately.

Specify 3S unless you have a specific reason not to. The D30C range carries 200 mA and 300 mA output ratings depending on variant; check the load current your solenoid or relay actually draws rather than assuming.

Flush and non-flush mounting

One decision the code does not cover but that matters mechanically: whether the sensor is designed to be mounted flush in metal or must stand proud. Shielded sensors can be embedded in a metal bracket; unshielded sensors sense further but need a clear zone around the face. Mounting an unshielded sensor flush in steel makes it trigger on the bracket. Our note on shielded versus unshielded sensors covers the clearances.

The rest of the range

The D30C covers DC inductive switching. Adjacent needs are served by other series:

• D32C capacitive — for plastic, liquid, powder, wood and glass
• D20C NAMUR — for intrinsically safe and hazardous-area duty
• D31C photoelectric — where the sensing distance exceeds inductive range
• A20C AC two-wire — for retrofits into panels with no DC supply available
• Magnetic switches — for sensing through non-ferrous walls

Ordering

If you know the code, send it. If not, send the target material, the sensing distance required, the body size your mounting allows, the output your input card expects, whether the function should be NO or NC, and the supply voltage. We will return the part number and price. Non-standard cable lengths and connector options are available on request — worth asking about on any order above a handful of pieces, because it usually removes a junction box from every machine.

Dealer, distributor, authorised distributor, channel partner, reseller. In Indian industrial supply these words get used interchangeably, and they describe very different commercial relationships. The distinction is invisible when everything works and extremely visible when something fails.

Here is what each route actually is, what it is good at, and how to tell which one you are dealing with.

The four routes, honestly described

Direct from the manufacturer. You buy from whoever built the product. Best technical depth, best access to variants, best position on a warranty claim. Usually the right route for volume, for anything non-standard, and for products that will be supported over a plant lifetime.

Authorised distributor. A contracted relationship with the manufacturer, carrying factory warranty and factory technical escalation. This is the standard route for imported product — it is how a German or Swiss manufacturer serves India without operating here directly. Accent holds this relationship for Novotechnik and Contelec across India and SAARC.

Stockist or dealer. Buys from distributors, holds inventory, sells locally. Genuinely valuable when you need something today and the alternative is a week. The trade-off is that technical support is thin and the range is whatever moves fastest.

Reseller or trader. Buys wherever the price is lowest, including from other markets. Sometimes a legitimate surplus channel. Sometimes grey-market product with no supported warranty route. The difficulty is that it looks identical to the other three on a website.

When going direct is worth the effort

Direct is not automatically better. It is better in specific situations:

• Volume orders. Pricing improves, and production can be scheduled against your delivery dates rather than drawn from someone inventory.
• Anything non-standard. A specific cable length, a different connector, a housing variant. Dealers cannot authorise these; manufacturers can quote them.
• Difficult applications. When the sensing problem is genuinely hard, you want the person who understands the electronics, not the person who understands the catalogue.
• Long-life plant. A direct relationship with a manufacturer survives longer than a dealer relationship, and matters when you need the same part in year eight.
• Certification requirements. Documentation comes from the manufacturer. Going through intermediaries adds delay and loses papers.

When a local stockist is the right answer

When the line is down and the part is standard. A stockist two hours away with the right M18 PNP switch on the shelf beats a better price arriving Thursday. Buy the emergency locally, then fix the underlying spares holding afterwards.

How to spot grey-market stock

This is the practical risk in the Indian market, and it is worth knowing the signals.

1. The price is well below everyone else. Distribution margins are not large. A price substantially below the market usually means the product came in through an unofficial route, or it is old stock, or it is not what the label says.
2. The seller will not put authorised in writing. Ask directly. An authorised party confirms it immediately.
3. They cannot produce a full ordering code. Series names are public. Configuration codes come from the manufacturer ordering system.
4. The warranty is theirs, not the manufacturer. A seller-backed warranty on imported product is the clearest signal there is.
5. No documentation, or documentation later. Declarations of conformity and test certificates should accompany the goods.
6. Vague delivery. Authorised channels can tell you whether something is in stock in India, in stock at the factory, or on a production run. Traders often cannot, because they are sourcing it after you order.

What we do

Accent occupies both positions, which is unusual and worth being explicit about.

For inductive, capacitive, photoelectric, magnetic and NAMUR proximity switches, we are the manufacturer — built in Mumbai since 1985 to IEC 60947-5-2, with variants quoted on request.

For Novotechnik linear and rotary position sensors, and for Contelec, we are the sole authorised distributor for India and SAARC, carrying factory warranty and factory engineering escalation.

The practical benefit is that one enquiry can cover both. A machine that needs twelve proximity switches and two linear transducers does not need two suppliers, two purchase orders and two warranty routes. If you want to verify the distribution claim rather than take it on trust, our guide on checking authorised Novotechnik stock explains exactly how.

Search for proximity sensor manufacturers in India and you will get a long list. Most of the companies on it do not manufacture anything. They import, they rebadge, or they assemble from bought-in modules — all legitimate businesses, but not the same thing, and the difference matters once you need a variant, a certificate, or a replacement for a part you bought four years ago.

This is the checklist we would use ourselves. It is deliberately written so that it can be applied to Accent as easily as to anyone else.

1. Ask what standard the product is built to

For inductive and capacitive proximity switches, the relevant standard is IEC 60947-5-2. It defines sensing distance and its tolerances, the standard target, switching frequency, and the behaviour that makes one manufacturer sensing distance comparable with another.

A supplier who cannot name the standard their product is built to is telling you something. A supplier who quotes a sensing distance without specifying whether it is rated, effective or assured operating distance is telling you something more subtle but just as useful — those three numbers differ, and the gap between them is where field failures live.

Accent manufactures to IEC 60947-5-2. Ask us for the figures against that standard and we will give them to you.

2. Ask to see where it is made

Not a photograph of a building. Ask whether you can visit, and watch how the question is received. A manufacturer will treat a plant visit from a serious buyer as normal. An importer will find reasons.

Our factory is in Vikhroli, Mumbai, and has been producing sensors since 1985.

3. Ask whether they can make a variant

This is the fastest way to establish what a supplier really is. Ask for a non-standard cable length, a different connector, or a specific housing material. A manufacturer will quote it, with a lead time and a quantity threshold. A reseller will explain why the catalogue option is better for you.

Variant capability is not a luxury. On an OEM machine build, being able to specify the exact cable length removes junction boxes, cable management and installation labour from every unit you ship.

4. Ask what happens to a part number in five years

Industrial plant outlives industrial catalogues. The question that matters on a twenty year asset is whether the same part will still be available, or whether you will be in a cross-reference exercise trying to establish what replaces it.

Importers are exposed here in a way manufacturers are not — when the overseas principal rationalises a range or changes distributor, the Indian supplier loses the part regardless of what they promised you.

5. Ask about traceability

Can they tell you which production batch a given serial number came from? If you are supplying into automotive, pharmaceutical or export machinery, your own quality system probably requires component traceability, and discovering at audit that your sensor supplier cannot provide it is an unpleasant surprise.

6. Separate the sensing distance claim from the application

A headline sensing distance is measured against a standard mild steel target under standard conditions. Your target is probably not that. Stainless steel, aluminium, brass and copper all reduce the effective sensing distance, some of them substantially — the correction is real and predictable, and a manufacturer will apply it for you without being asked.

If a supplier quotes the catalogue distance for an aluminium target without mentioning the reduction factor, they have not understood the application. Our note on reduction factors for different metals covers the arithmetic.

7. Check the range covers the awkward cases

Every supplier stocks M18 and M30 DC three-wire PNP. The range is tested by the things you need occasionally:

• NAMUR versions for intrinsically safe and hazardous-area duty
• Capacitive switches for non-metallic targets and level detection
• Magnetic switches for sensing through non-ferrous walls
• Photoelectric switches where the sensing distance exceeds inductive range
• Control units and amplifiers to complete the loop
• AC two-wire versions, for retrofits into older panels that have no DC supply available

A supplier who has only the easy part of the range will leave you sourcing the rest from three other vendors.

8. Ask who answers a technical question

Not the sales contact — the engineer. On a difficult application, the value of a supplier is concentrated in the twenty minutes someone spends working out why a sensor is chattering. If there is no one to ask, the catalogue was the whole product.

Where imported product still wins

An honest checklist needs this section. Imported product is the right answer when you need something genuinely specialist that is not made domestically — high-precision absolute position measurement being the obvious case. That is why we distribute Novotechnik alongside our own manufacturing rather than pretending an inductive switch can do a linear transducer job.

The useful question is not Indian or imported. It is whether your supplier is willing to tell you which one your application actually needs.

The RFC-4800 is Novotechnik robust touchless absolute rotary sensor, and it is the unit we are asked for most often when an application has already destroyed something else. That is not an accident — the reason buyers arrive at this series is almost always that a contacting sensor has worn out, or that the shaft cannot be mechanically coupled at all.

This guide sets out what the series does, the interface decision that drives the ordering code, and how to choose between the RFC-4800 and the RSC-2800.

What touchless actually buys you

In a traditional potentiometric rotary sensor, a wiper rides on a resistive track. That design is accurate, cheap and very well understood, and it has one inherent limitation: the wiper and the track are in physical contact, so they wear. In a high-cycle application the track eventually develops a worn band, and the output becomes noisy exactly in the region the machine uses most.

The RFC-4800 uses NOVOHALL magnetic sensing instead. A magnet moves with the shaft, the sensing element reads the field, and nothing touches anything. Three consequences follow:

• Cycle life stops being the limiting factor. There is no measuring-path wear mechanism to consume.
• The sensor can be sealed more thoroughly, because there is no requirement for a mechanical path into the measuring element.
• Mechanical decoupling becomes possible. In some configurations the magnet and the electronics can be separated, which matters where the shaft cannot accept a coupling or where vibration would destroy a coupled unit.

It is absolute, so position is known at power-up without a reference run — important on equipment that must resume safely after a power failure rather than homing first.

The interface decision

The RFC-4800 carries an unusually broad interface range: analogue, digital and fieldbus. That breadth is the main reason it gets specified into machine builds rather than just repairs.

Analogue — voltage or current, for conventional PLC analogue inputs. Current output remains the safer choice on long cable runs and in electrically noisy plants.

Digital — absolute serial output, avoiding the resolution loss and drift of an analogue chain. Worth specifying where accuracy is the point of the exercise.

Fieldbus — the option that distinguishes this series in practice. If your machine is already built around a bus, taking position onto the bus removes an analogue input card, the associated wiring, and a calibration step. We see steady Indian enquiry volume for CANopen position sensors specifically, mostly from machine builders standardising on a single bus across a platform.

Confirm the exact protocol and profile your controller expects before ordering. Fieldbus variants are configured to the protocol, and this is not something that can be changed after delivery.

RFC-4800 or RSC-2800?

Both are touchless NOVOHALL single-turn rotary sensors from the same manufacturer, so the choice is rarely about accuracy. It is about how the sensor mounts and what it has to talk to.

• Choose the RSC-2800 when you want a compact shaft-type unit with a straightforward analogue, SSI, incremental or SPI interface, and the mechanical arrangement allows a normal coupling. It also offers ratiometric output and E1 type approval, which matters for mobile machinery.
• Choose the RFC-4800 when the application is mechanically hostile, when you need fieldbus, or when the installation would benefit from separating the magnet from the electronics.

If you are unsure, send us the mechanical arrangement and the controller type and we will tell you which is the better fit. The wrong answer here is usually discovered at commissioning, which is the expensive moment to discover it.

Specifying it correctly

The information that pins down an RFC-4800 ordering code:

• Measuring angle required, and whether it must cover a full 360 degrees
• Interface, and for fieldbus the exact protocol the controller speaks
• Supply voltage available at the sensor
• Protection rating demanded by the environment, including washdown regime
• Worst-case temperature at the mounting point, not the plant ambient
• Mechanical arrangement — shaft diameter, available depth, and whether a coupling is possible at all
• Whether redundant outputs are required for a safety function

Buying it in India

Accent Controls is the sole authorised Novotechnik distributor for India and SAARC. Ordering through the authorised channel means factory warranty, traceable supply and an engineering route back to the manufacturer if the application turns out to be unusual. Our guide to verifying authorised Novotechnik stock covers the checks worth running on any supplier, including us.

The RSC-2800 is one of the most frequently specified Novotechnik rotary sensors in India, and one of the most frequently mis-ordered. The reason is simple: RSC-2800 is not a product, it is a family. Six interface options, three protection bands, an unusually wide temperature range and optional redundancy mean that two units carrying the same series name can behave quite differently on the machine.

This guide walks through the decisions that set the ordering code, so that what arrives is what your control system expects.

What the RSC-2800 is

It is an absolute, non-contacting rotary sensor built on Novotechnik NOVOHALL magnetic technology. Absolute means it reports true shaft angle immediately at power-up, with no homing move and no reference run. Non-contacting means there is no wiper riding on a resistive track, which removes the dominant wear mechanism in traditional potentiometric rotary sensors.

That combination is why it turns up on mobile machinery, on automotive test rigs, and on plant equipment where a sensor failure means a shutdown rather than an inconvenience. There is no mechanical contact in the measuring path to wear out.

Decision one: the interface

This is the choice that most often goes wrong, because the series supports six and the label does not always make the difference obvious.

• Voltage output — the default assumption for most PLC analogue input cards. Simple, well understood, and sensitive to cable length and ground offset over long runs.
• Current output — the right answer whenever the cable run is long or the environment is electrically noisy. A current loop does not care about voltage drop down the cable, which in an Indian plant with a 40 metre run back to the panel is usually the deciding factor.
• Ratiometric — output scales with supply voltage rather than holding an absolute value. Correct when the receiving controller shares and measures the same supply, wrong when it does not. Worth checking carefully, because a ratiometric unit fed into a fixed-scale input reads plausibly but drifts with supply.
• SSI — synchronous serial, for absolute digital position without analogue conversion losses. Choose this when resolution matters and the controller supports it.
• Incremental — pulse output, for retrofits into counters and drives already built around incremental feedback.
• SPI — for direct integration into embedded electronics rather than a plant PLC.

If you are replacing an existing sensor, match the interface to what the controller is wired for, not to what seems technically better. An upgrade from voltage to SSI is a control system change, not a sensor swap.

Decision two: protection rating

The RSC-2800 is available from IP54 up through IP65 and IP67. The practical guidance:

• IP54 is adequate inside a reasonably clean enclosure, where the sensor sees dust but never direct water.
• IP65 handles hose-down and general plant wash.
• IP67 covers temporary immersion — the right choice for mobile machinery, outdoor installation, and anywhere monsoon exposure is realistic.

Specify by the worst case the unit will actually see, not the normal condition. The failure mode for an under-rated sensor is water ingress at the cable entry, and it typically appears months after commissioning.

Decision three: temperature range

The series covers from below minus 40 degrees Celsius up to above plus 85. Very few Indian applications need the cold end, but the hot end matters more than people allow for. A sensor mounted near a furnace, on a hydraulic power pack, or inside an unventilated panel in a Gujarat summer can sit far above the ambient air temperature. Measure at the mounting point in the worst month rather than taking the plant ambient figure.

Decision four: redundant outputs and E1 approval

Two options exist on this series that are worth knowing about before you need them.

Redundant outputs provide two independent measuring channels in one housing, so a controller can cross-check them and detect a fault rather than acting on a wrong reading. If the angle measurement feeds anything safety-related, raise this at the enquiry stage — retrofitting redundancy means changing the sensor.

European E1 type approval is available on this series. If you are building vehicles or mobile machinery for export, confirm whether your compliance route requires it before you order.

Mechanical fit

The RSC-2800 is a shaft-type design. The mating question is the coupling: a rigid coupling transfers any shaft misalignment straight into the sensor bearing and shortens its life, so a flexible or backlash-free coupling is normally the right choice. If you are replacing a blind hollow shaft unit, note that RSC-3200 is the hollow-shaft member of the same family. Novotechnik no longer recommends it for new designs, so treat it as a like-for-like replacement part rather than a specification for a new machine, and ask us for the current equivalent.

Ordering

Send us whichever of these you have and we will return the full ordering code with a price and a drawing:

• Measured angle range in degrees
• Output type, and the controller or input card it feeds
• Supply voltage available at the sensor
• Protection rating required, and whether washdown occurs
• Worst-case temperature at the mounting point
• Whether redundant outputs are needed
• The existing part number and a photograph of the label, if this is a replacement

Accent Controls is the sole authorised Novotechnik distributor for India and SAARC, so the quotation covers factory warranty and traceable supply. See also our guide to checking you are buying authorised Novotechnik stock, and the wider single-turn rotary sensor range.