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Inductive Proximity

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Altech offers a comprehensive line of Inductive Proximity Sensors to satisfy today s diverse sensor applications. Used for a wide range of functions in industrial plants and machinery, typical sensor applications include; material handling systems, machine tools, packaging machines, assembly machines and production lines, robotic systems, etc.

Altech / Pulsotronic Inductive Proximity Sensors are available for DC (PNP and NPN), AC and AC/DC voltages with normally open and normally closed output contacts, in flush and non-flush mounting configurations. They are available in Cylindrical, Limit, Block and Ring styles.

Pulsotronic Proximity Sensors:

  • 25 years of proven quality and reliability
  • ISO 9001 Certified Manufacturing
  • Selection of Fixed Cable or Quick Disconnect Connectors
  • Choose from Cylindrical, Limit Style, Block and Ring Sensors
  • Immediate delivery of most models
  • Featuring Versa-Prox, our new line of rotatable, 17-position Limit Style Sensors
  • Short circuit, overload and reverse polarity protection for DC models


  • Digital output is standard. Analog output is available.
  • Meet or exceed IP67 (NEMA 1,3,4,6,12,13) protection standards.
  • 10 - 30 VDC and 20 - 250 VAC, up to 500 mA current.
  • 0.5mm to 70mm (0.02 to 2.76 in.) Sensing range.


The Inductive Proximity Sensor (IPS) is a solid state device that generates an output signal when metal objects are either inside or entering into its sensing area from any direction. No physical contact is required nor desired. IPS's work best with ferrous metals, however, they also work well with non-ferrous metals (aluminum, brass, copper, etc.) at reduced sensing distances, see Figure 1.

First introduced in the mid 60’s, Inductive Proximity Sensors were designed as an alternative to mechanical limit switches for many applications. Initially, IPS's were made with housing similar in size and dimension to the limit switch, but had short sensing distances. Following very good results with these new devices, market pressure led to the development of larger sensors with increased sensing distances.

Inductive Proximity Sensors have no moving parts, operate very fast, are extremely reliable, require no maintenance, and operate under extreme environmental conditions. They typically interface with Programmable Logic Controllers (PLC), process, and personal computers with appropriate hardware and software. They also can control relays, solenoids, valves, etc., up to their maximum output current.

Altech Inductive Proximity Sensors are manufactured by Pulsotronic in Germany. Pulsotronic, a well known European manufacturer, has been designing and manufacturing IPS's for over 30 years using state-of-theart technology and is an 1S0 9001 certified company. Altech is Pulsotronic's North American marketing partner. Our Inductive Proximity Sensors meet National and International Standards and carry the CE Mark.

Altech offers 4 Inductive Proximity Sensor families. Cylindrical Inductive Proximity Sensors represent the most popular device, and are available in diameters from 4mm (.159 in.) to 30mm (1.18in.) and sensing distances up to 40mm (1.57in.). Typically, Cylindrical models have low sensing distances and are used in applications requiring compact sizes that are easily mountable. Please refer to selection guide on pages 12-14 for more information.

Limit style (Versa-Prox) Inductive Proximity Sensors are physically larger than Cylindrical IPS's and have sensing distances up to 40mm(1.59in.). These units feature a unique 17 position rotating sensing head with snap and lock construction (no screws). Versa-Prox IPS's are used to replace mechanical limit switches and for applications where adjustment of the sending head is desired.

Block Inductive Proximity Sensors feature models with adjustable sensing distances up to 70mm (2.78in.). The largest Block is 100 x 50 x 40 mm (3.9 x 2 x 1.6 in.). Block sensors are used for applications where maximum sensing distances are required.

Ring Inductive Proximity Sensors are special devices that detect metal objects passing through the ring. Altech offers a wide range of ring diameters from 12mm (.47in.) to 300mm (11.91 in.). Our Ring IPS's are available in normal and high sensitivity models. Typical application are in stamping operations and detection for unwanted metals.

Altech/Pulsotronic Inductive Proximity Sensors, (except Ring & Flat-pack), offer a lifetime warranty subject to completing the registration form.


An Inductive Proximity Sensor consists of an oscillator, a ferrite core with coil, a detector circuit, an output circuit, housing, and a cable or
connector, (see Figure 2). The oscillator generates a sine wave of a fixed frequency. This signal is used to drive the coil. The coil in conjunction with ferrite core induces a electromagnetic field. When the field lines are interrupted by a metal object, the oscillator voltage is reduced, proportional to the size and distance of the object from the coil. The reduction in the oscillator voltage is caused by eddy currents induced in the metal interrupting the field lines. This reduction in voltage of the oscillator is detected by the detecting circuit. In standard sensors, when the oscillator voltage drops below a present level, an output signal is generated. In an Analog Proximity Sensor, a pre-set level is not used. The Analog sensor circuitry utilizes the change of the oscillator output voltage to generate a DC output voltage proportional to the distance the metal object is from the sensing head.

Most Altech Inductive Proximity Sensors are available in DC (10-30 VDC), AC (90-250VAC), AC/DC (20-250VAC/DC). Please refer to each product specification page for specific operating voltages.

Altech offers a range of IPS's with different output ratings from 5mA to 500mA. Please refer to each product specification page for specific output current.

Outputs may be Normally Open (NO) or Normally Closed (NC). Some models feature both a normally open (NO) and normally closed (NC) output which is called a complementary output. Limit style Versa-Prox sensors feature a programmable Normally Open (NO) and Normally Closed (NC) output.

DC Inductive Proximity Sensors may be 2-wire, 3-wire or 4-wire. A 3 -wire or 4-wire DC sensor can be an NPN or PNP output transistor. If the output load is connected to the negative power source then a sensor with a PNP output transistor is required. A PNP sensor is also known as a source sensor. If the output load is connected to the positive power source, then a sensor with an NPN output transistor is required. An NPN sensor is also known as a sink sensor. Please see Figure 3 for PNP and NPN electronic output circuits. AC Inductive Proximity Sensors are 2-wire devices, except when using a sensor with a metal housing where a third wire is available for connection to system ground.

Altech Inductive Proximity Sensors use a variety of metal and nonmetallic housing materials. Please refer to each product specification for specific information on housing materials, and page 136 of this catalog.

Altech offers Inductive Proximity Sensors that feature either 2 meter fixed PVC cable or a variety of quick disconnects. All quick disconnect models require an optional matching cable assembly. Custom cable lengths and material choices are also available. For more information, please refer to each product specification or the cable assemblies section on pages 116-121.

Flush Mount sensors are sometimes called Shielded or Embeddable. A metal band surrounds the sensing head which contains a coil wound around a ferrite core as in Figure 4.

The resulting electromagnetic field is directed in front of the sensor face. Flush sensors have a narrow sensing field which may be desirable in certain applications. In a Non-Flush (Non-shielded or Non-embeddable) sensor, (Figure 4), there is no metal band and the resulting electromagnetic field lines are much wider than the sensor face. Non-Flush sensors have a larger sensing distance than Flush sensors.


Sensors may be wired in series or parallel. Please contact Altech for more information.

PROTECTION (Electrical)
Most of the Inductive Proximity Sensors Altech offers have short circuit, overload, reverse polarity, and wire break protection. Please refer to the Technical Glossary pages 135-136, and the product specification for more information.

PROTECTION (Sensor Housing)
All Altech sensors are rated in accordance with IEC Publication 529 which describes degrees of protection that enclosures or sensor housings are designed to provide, the degree of protection is indicated by two letters (IP) and two numerals, for additional information see the product specification and pages 132-133.

All Inductive sensors meet the following shock and vibration requirements: 30g’s/11ms, and 10-55 Hz/mm.

There are several sensing distance definitions used in industry. The nominal sensing distance (Sn), is the conventional quantity to designate the operational distance, it is specified in the ordering pages, and does not include variations in production tolerances, supply voltage tolerances, and ambient temperature tolerances.

A standard target used to specify sensing distance is a square piece of mild steel having a thickness of 1mm (0.04 in.). The sides of the square are equal to the diameter of the circle inscribed on the sensor face or three times the rated operating distance Sn, whichever is greater.

The assured operation distance (Sa) is the smallest useful sensing distance which guarantees operation under variations in temperature, voltage and manufacture. It is given as 81% of Sn. See Figure 5. 0<Sa<.81 Sn.

The effective sensing distance (Sr), is measured at nominal supply voltage and nominal ambient temperature and takes into account manufacturing tolerances:
0.9 Sn²Sr² 1.1 Sn

The usable sensing distance, (Su), takes into account temperature, voltage variations and manufacturing tolerances:
.81 Sn² Su ³ 1.21 Sn


Hysteresis is the switch-on point when the object approaches the sensor's active surface, and switchoff point, when the object is moving away from the sensor's active surface. Without sufficient Hysteresis, an Inductive Proximity Sensor would chatter (continuously switching on and off), so it is designed into the sensor circuitry. The differential travel (Hysteresis) is given as a percent of the expected rated operating distance Sr. (See Figure 6).


The switching frequency indicates the maximum number of switching operations of a sensor per second. The value listed in the product specifications is achieved with the conditions shown in Figure 7. The value is always dependent on target size, distance from sensing face and speed of target. Using a smaller target or space may result in a reduction of a specific sensor maximum switching frequency.


Altech offers a full range of accessory products including quick disconnect cable assemblies, mounting clamps and brackets, liquid tight strain reliefs, amplifiers, switching units, etc. Please refer to each product specification and the accessory chapter starting on page 113.



The CE Mark is a compliance symbol, which means that the product meets the standards set by the European Committee for Electrotechnical Standardization (CENELEC), and the International Electrotechnical Commission (IEC). Products containing the CE mark are allowed to have free movement within the European Union (EU), and European Economic Area (EEA). Products manufactured in the USA that are exported to the EU and EEA should have the CE marking and utilize components also having the CE marking.


Altech Cylindrical sensors are available in diameters ranging from 4mm (.16 in.) to 30mm (1.18 in.) with sensing distances up to 40mm (1.57 in.). Most models feature nickel plated brass (BN) housing, but stainless steel (SS) and non-metallic versions are available. Both flush mount and non-flush mount sensors are available. Flush mount versions are often called shielded or embeddable. Non-flush mount sensors are also called non-shielded or nonembeddable. Non-flush sensors have larger sensing distances than their flush mount counterparts. All Inductive sensors meet IP67 (NEMA1, 3, 4, 6, 12, 13) protection levels. Please refer to pages 132-133 of this catalog for more information.


Flush Mounted, sometimes called embedded or shielded sensors, have electromagnetic fields concentrated directly in front of the sensing heads and may be mounted directly into metal mounting brackets or embedded directly into metal without causing a false output. Figure 8 also illustrates that on Cylindrical Flush Mount sensors there should be at least 1 diameter of distance between adjacent sensors, and no non-target metal surfaces should be less than 3 times the sensing distance Sn directly across from the sensing head. Also, two directly opposite sensors mounted in metal should be greater than 6 times the sensing distance apart.

NON-FLUSH CYLINDRICAL SENSORS Sometimes called non-embedded or non-shielded, non-flush sensors have electromagnetic fields with a wide sensing angle and are unshielded (no metal surrounding the sensing head). Care must be taken to insure that no non-target metal comes in near proximity to the sensing head. Distances are demonstrated in Figure 8. Adjacent sensors should be separated by at least 2 times the diameter. Non-target metal should be at least 3 times the sensing distance directly across from the sensing head. Two directly opposite sensors should be at least 6 times the sensing distance apart.

OUTPUT CONNECTIONS AC,DC – Normally Open (NO), and Normally Closed (NC). DC Namur – Special interface Circuits required. DC Analog – Analog Output 1 to 9V.

OUTPUT CABLES Cylindrical Sensors are provided with 2 meter PVC fixed cables. 5 meter PVC, 2 and 5 meter PUR cables are optional and specified by selection of the last two digits of the part number. See chart below. Cable Length Part No. & Material Last Digits 2m PVC 00 5m PVC 02 2m PUR 10 5m PUR 12

QUICK DISCONNECT CONNECTORS Pulostronic sensors are available in a wide selection of Quick Disconnect styles for DC and AC circuits. While virtually any sensor can be custom manufactured with a Quick Disconnect connector, Altech offers one of the largest selection of standard Quick Disconnect models. Quick Disconnect models are designed to be user-friendly and to simplify installations. Please see the product specification for sensors with quick disconnect connectors and matching cable assemblies on pages 116 to 121 in the accessory section.

HOUSING MATERIALS AC – Nickel Plated Brass Trogamid T Teflon Plated Brass DC – Nickel Plated Brass Trogamid T Teflon Plated Brass Stainless Steel


LIMIT STYLE INDUCTiVE PROXIMITY SENSORS The Limit Style Inductive Proximity Sensor features a housing with a similar outline of a mechanical Limit Switch which it has replaced in many applications. All Altech Limit Style models are 41mm (1.61 in.) x 40mm (1.57 in.) x 121 mm (4.76 in.). The Altech Versa Prox® construction features a rugged design that is capable of moving the sensing head into 17 unique positions. Once the positioning is completed, the Versa Prox® can be snapped and locked into position with no screws.

For connecting wiring to the Versa Prox®, the unit separates once the locking mechanism is disengaged, and a terminal strip is available for connections. The hole opening is a threaded 1/2” 14NPT. Please see page 70 for detailed instruction for adjustments.

The Versa Prox® has 2 LED and 3 LED models, they have programmable, Normally Open or Normally Closed outputs, and both Flush or Non-Flush models are available. All sensors meet IP67 (NEMA 1,3,4,6,12,13) protection levels.

FLUSH MOUNT SENSORS Flush Mounted Sensors have electromagnetic fields concentrated directly in front of the sensing head and may be mounted directly into metal mounting brackets or embedded directly into metal without causing a false output. Figure 9 illustrates that on Limit Style sensors there should be at least the sensor width separating adjacent sensors. Also, no non-target metal should be less than 3 times the sensing distance Sn directly across the sensor. Two sensors directly across from each other should be greater than 6 times the sensing distance Sn.

NON-FLUSH MOUNT SENSORS Non-Flushed Mounted Sensors have electromagnetic fields with a wide sensing angle and are internally unshielded (no metal surrounds the sensing head). Care must be taken to insure that no nontarget metal comes in the sensing head area as shown in Figure 10. The sensing head must extend 40mm(1.57 in.) in front of metal, two sensors directly across from each other should be greater than 6 times Sn, the sensing distance. Adjacent sensors should be spaced greater than 280 mm (11.02 in.) center-tocenter.

OUTPUT CONNECTIONS – 1/2" - 14NPT Threaded Hole Opening and Terminal Block. – Micro Style Quick Disconnect Connector.

HOUSING MATERIAL PA6.6 (GV-30) – Versa Prox® Models. Trogamid T – Standard Models.

DC VOLTAGE LED FUNCTIONS L Series Condition LED Color Power Green Output Orange Overload Green LED Flashes

GL Series Condition LED Color Power Green Output Orange Adjust Red Unsafe Condition Red (Adjust) LED flashes when target is detected. Correct Setting Orange (Output) LED lights when distance is reduced

AC VOLTAGE LED FUNCTIONS Condition LED Color Power Green Output Orange

AC/DC VOLTAGE LED FUNCTIONS Condition LED Color Power Green Output Orange Overload/Short Green LED flashes. Circuit To reset sensor, disconnect supply voltage for 2 seconds.


BLOCK INDUCTIVE PROXIMITY SENSORS The Altech Inductive Proximity Block Sensor family has a wide selection of housings, with both fixed and adjustable sensing range. Units are available in DC, AC and AC/DC operating voltages.


FLUSH MOUNT VS. NON-FLUSH MOUNT Block Sensors that are flush mount and have electromagnetic fields directly in front of the sensing head may be mounted directly into metal without causing a false output. The sensing head must be clear or any non-target metal. Block sensors that are Non-Flush mount have electromagnetic fields with a wide sensing angle. Therefore care must be taken to ensure that no non-target metal comes in contact with the sensing head. See Figure 11 for mounting details.

OUTPUT CONNECTIONS Block sensors are available in 2 meter fixed PVC output cables, quick disconnect connector, or 1/2” 14NPT hole opening for wiring to a terminal block. Please see selection guide on pages 82-83 and the product specification for more information.

HOUSING MATERIAL The following housing materials are used for housings in the Block Sensor family: Aluminum PBTP (GV-30) Trogamid T Aluminum/Trogamid T Nickel Plated Brass


RING STYLE INDUCTiVE PROXIMITY SENSORS Altech Ring Sensors are used for variety of applications including punching and stamping operations to detect small metal parts and for the identification of metallic contamination in bulk materials. The sensitivity of all Altech Ring Sensors is given in terms of a steel metal ball diameter. This is the minimum diameter steel ball that the sensor will detect. Non-ferrous materials will require larger diameter parts for correct sensor detection. See page 4, Figure 1 for rated operating distance correction factors.

OUTPUT CONNECTION Mini Ring – Normally Open (NO) Standard Ring – Complementary High Sensitivity – Complementary Analog – 1-9 Volt Analog

RING SENSOR MOUNTING When high sensitivity ring sensors are mounted in or near non-target metal objects, care must be exercised in accordance with the recommendations on the diagram. See Figure 12.


General Information
Altech accessories are available as optional equipment to assist in the use of sensor products. Some sensor products require specific accessory units in order to perform satisfactory. Please consult the product specification to determine which accessories are essential. The accessories include mounting brackets, cable assemblies, switching amplifier units, and motion detector systems.

MOUNTING BRACKETS Several fixtures are available that provide the ability to mount cylindrical and limit style sensors.

CABLE ASSEMBLIES Altech offers one of the largest Quick Disconnect selection of sensors in the industry and matching cable assemblies. Standard Sensors come with 2 meter fixed PVC cables, but to improve maintenance and mean time to repair (MTTR) quick disconnect sensors with matching cable assemblies are desirable. For DC Sensors Altech offers a mini- style 4-pin cable assembly, a micro style 3- and 4-pin cable assembly, and a pico style 3-pin cable assembly. Most are available in straight or 90° molded cable connection, and the micro and pico styles are also available with 2 LED’s. For AC Sensors Altech offers a mini- style 3-pin cable assembly, a micro style 3-pin and 4-pin cable assembly.

SWITCHING/AMPLIFIER UNITS Altech offers a wide variety of products used in conjunction with Ring Sensors, Analog Sensors, Namur Sensors, testers and power supply modules for all sensor products.

MOTION DETECTOR SYSTEMS Motion detectors accept impulses from proximity sensors when a repetitious event is occurring. These impulses are measured compared to a standard. The motion detector will “Time Out” between impulses and provide an output for over or under the set speed. Altech offers completely contained motion detector systems, including built-in proximity sensors or as separate components.

For more information contact Altech at:
908-806-9400 • 908-806-9490 (FAX) • • 35 Royal Road, Flemington, NJ 08822