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What is a power sensor?  

A Power Sensor measures either current or voltage and provides output on monitored parameter levels to a control system.  Current sensors are capable of measuring both AC and DC current, in order to monitor power use and provide diagnostics for electrically-powered equipment.  Applicable on nominal circuits of 120V, 240V and 480V, Voltage Sensors provide a fully isolated analog output proportional to rated nominal voltage in both sinusoidal and non-sinusoidal (variable frequency) situations. 

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How does a power sensor work?

A Safety Interlock Switch is designed with special features to ensure reliable operation and protect against tampering. 

Non-Contact interlock switches

Non-Contact interlock switches were specifically developed for monitoring protective covers such as doors, flaps and covers. The potential-free contacts are controlled by multiple magnets in the actuator, which makes the devices especially tamper-proof. The assembly comprises a sensor component and a separate magnet actuator component. The sensor is typically mounted to a stationary portion of a structure and the magnet to a movable portion. When the sensor and the actuator are within operating range, the NC contacts will be closed and the NO contacts will be open.

Key interlock and safety limit switches

For Key Interlock and Safety Limit Switches, two different principles of operation ensure the mechanical securing action: magnetic-force interlocking (open-circuit principle) and spring-force interlocking (closed-circuit principle). Key Interlock switches are designed with two parts— the sensor and the actuator. The sensor is typically mounted on the stationary portion of a structure and the actuator is mounted on the movable portion. The sensor is designed to work with the correct actuator (key) to reduce tampering and increase safety. Actuation of the interlock switch occurs only when the corresponding key is inserted into the key slot. The key is usually mounted on a door or machine guard in such a way that when the door or the guard is closed, the key fits into the slot actuating the switch. The special key design makes the safety interlock switch extremely difficult to defeat. When inserted into the slot, the key performs three separate mechanical functions.

Power sensors components

Current sensor

  • Output Terminals: Wiring point for sensor output connection.
  • Core Connection: This part of the sensor housing has an attachment clip for Split core sensors and is fixed in place for Solid core sensors.
  • Mounting Base: Built in pre-drilled mounting surface.  Serves as an attachment point for DIN rail mounting accessory.
  • Sensing Aperture: Current-carrying conductors pass through this aperture, and the current is measured by the sensor electronics.
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Voltage sensor

  • Output Terminals: Wiring point for sensor output connection
  • Input Terminals: Wiring point for line voltage connection
  • DIN Rail mount: Built-in mounting clip for direct attachment to DIN rail
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Why you choose a power sensor for a motor monitoring application

 
  • Very robust and survivable
  • NO or NC solid-state outputs for control circuits up to 120 VAC/VDC or 240 VAC/VDC
  • Some models self-powered to cut installation and operating costs
  • Compact space-saving 35mm enclosure great for applications with space constrictions
  • High sensitivity to detects currents as low as 0.5 A without wrapping the conductor around the sensor several times
  • Easily adjustable set points to increase application flexibly and speed start-up 
  • Input/output electrical isolation for improved safety
 
  • Solid or split-core housing versions tailored for each type of installation 
  • Some models featuring LED indication for quick visual indication of contact status
  • Built-in mounting feet for simple, two-screw panel mounting, or can be attached with the optional DIN rail-mounting kit accessory 
  • True RMS output allows for use in situations where power supplied is non-sinusoidal
  • Standard 4–20 mA loop powered output to work easily and reliably with existing control circuits

How to select a power sensor?

The first step is to review the application requirement and determine if voltage or current sensing is required.

For voltage sensing

EVT series VoltageWatch voltage sensors

  • High-performance, true RMS sensor for sensing voltage in single and three-phase installations.

For current sensing


Select the correct product family based on the sensing requirement

ECS series CurrentWatch AC current switches  

  • AC current switches for detecting overcurrent conditions

ECSC series compact CurrentWatch current switches 

  • AC/DC current switches for detecting AC current above 0.5 A trip point

ECSJ series CurrentWatch AC current switches  

  • Jumper selectable AC switches with solid-state output

ECS7 series CurrentWatch AC current switches   

  • Self-calibrating AC current switch with solid-state outputs

ECSTD series CurrentWatch AC current switches

  • AC current switches with time delay

ECSD series CurrentWatch DC current switches 

  • DC switch with solid-state or mechanical relay output

EAC series CurrentWatch AC current sensors 

  • ·AC current sensor with analogue outputs and power supply options
EACR series CurrentWatch RMS current sensors 
  • True RMS AC current sensing with 4–20 mA output

EDC series CurrentWatch DC current sensors

  • Ground fault sensors with solid-state or mechanical relay outputs

EGF series CurrentWatch ground fault sensors

  • ·Ground fault sensors with solid-state or mechanical relay outputs

EGFL series CurrentWatch ground fault sensors

  • Ground fault sensors with mechanical relays
 
Select a split core or solid core sensor based on the nature of the wiring to the device to be monitored.  If removing motor leads is difficult or impossible, split core sensors can allow for monitoring without disturbing the motor wiring connection.

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