Inductive Proximity Speed SwitchInductive Proximity Speed SwitchInductive Proximity Speed SwitchInductive Proximity Speed Switch

Inductive Proximity Switch

The PROX 120 is a micro-controlled, field adjustable inductive proximity switch with a 6.5 foot long cable, 4 character display and huge sensing range (6-30,000 RPM based on 1 pulse per revolution), providing flexibility in application and confidence in sensing. The pulses picked up by the sensor from a ferrous target are converted to an electrical signal at the rate of 4-million instruction cycles per second. Functions include simultaneous over-speed and under-speed monitoring. The unit is packaged in a NEMA 4/5 enclosure with a transparent Lexan™ cover for dust and moisture protection. This speed monitor utilizes a micro-controller and proprietary software routines to precisely monitor the rate of speed.

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Product Description

Product Sheet (PDF)


The Inductive Proximity Speed Switch is a non-contacting speed sensing device which converts pulses from a ferrous target to an electrical signal. It is a micro-controlled, field adjustable, multi–setpoint speed monitor, with a 4-character alphanumeric visual indication and relay output. Features include simultaneous Over / Under speed monitoring, programmable relay action, and non-contact sensing. The Prox 120 is packaged in a NEMA 4/5 enclosure with a transparent Lexan™ cover for dust and moisture protection.

Operating Theory

The speed monitor utilizes a micro-controller and proprietary internal software to precisely monitor the RPM rate of the rotating ferrous target(s). Time between pulses is compared to application appropriate, user defined settings.

Advantages & Specifications

Huge Sensing Range
– 6.0 to 30,000 RPM based on 1 pulse per revolution
– 1.0 to 7,500 RPM based on 4 pulses per revolution
– 0.1 to 3,000 RPM based on 60 pulses per revolution

Under & Over Speed
– 20-99% for Under Speed / 101-199% for Over Speed

– Easy to program • Field adjustable

LED Readout
– 4-Character display shows alarm status in low light

Durable Housing
– Epoxy coated aluminum housing • Lexan™ cover

Conduit Entry
– 1/2″ NPT for power / signal wires • 3/8″ for Prox wire

– Not directly coupled to a shaft

Proximity Sensor
– Includes 10-30VDC NPN M18mm Shielded N.O.
– 500 Hz, 6′ cable • 0.315″ sensing distance
– Will pick up any ferrous material – magnet not required

Temperature Range
– -40 to +158° F (-40 to +70° C)

– Nonvolatile, 10-year retention

Voltage Options
– 120/240 VAC or 24 VDC

Supply Current
– 100 mA Maximum

– Single Pole 10-A SPDT Relay • 250 VAC • UL/CSA

Frequency Range
– 0.1 Hz to 2500 Hz Controller / 500 Hz Prox Sensor

Application Considerations

• Verify Prox unit is compatible with voltage, process, temperature, construction and area classification.

• Sensor distance must be correct, secure and maintained for consistent operation.

• Proximity sensor detects the presence and absence or distance of metals, and should be located where the rotational process can be appropriately monitored.

• Install Prox unit according to National Electrical Code and / or local standards.

• Seal all conduit entries to the enclosure.

• Close transparent cover immediately upon program completion to minimize exposure to dust and weather.

• Do not use this device in explosive areas or locations classified as Hazardous. Unit is not designated for NEMA 7, 8, 9 or 10 locations.

Speed Conversions & Range Calculations

Operating range and conversion calculations from Hz to RPM are dependent upon the number of pulses per each revolution. With one pulse per revolution, 1 Hz is equal to 60 RPMs (one pulse per second X 60 seconds per min = 60 RPMs). Under-speed limit of 0.1 Hz equates to 6 RPMs.

Pulses may be manipulated by adding or subtracting vanes, bolt heads, spokes, holes, etc. in the monitoring device wheel or hub. The inductive proximity sensor detects ferrous (iron) metals best, but can also sense other metals. Sensing distance may vary depending on the metal and pulse vane configuration. The Prox 120 comes with a 500 Hz sensor.

Programming Specs

HSPD & LSPD: High and low speed alarm settings are percentage variables, based on the normal calibrated running speed of 100%. The Under-Speed value range is 20-99% of Full Speed, while Over-Speed is 101%-199%. Values outside the range will not be accepted.

Start-Delay: Programmable from 0 to 255 seconds, activated by initial power applied to the device. Delay will not re-occur until power is turned off and back on.

Programming Setup: INCR (Increment) and ENTER push buttons, and four character alphanumeric LED display along with STATUS and RELAY LEDs.

Program Settings: SDLY (Start-up Delay), LSPD and HSPD, RYFS (Relay Fail Safe Condition), ADLY (Relay Energize Delay), CDLY (Relay De-energize Delay), OKAY (Condition Indicator), ERR 0-9 (Trouble Shooting Info).

Relay Reaction Time: Independently Programmable from 0 to 255 seconds. Energized ADLY and De-Energized CDLY.

Product Sheet (PDF)

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