Arc Sensor - Industrial Microwave Dryers | Testing, Rental & Installation

Arc Sensor

ALS-900 arc sensor- cellencorALS-900

The ALS-900 arc sensor is a highly sensitive and intelligent light measurement instrument for detection of arcing within high power industrial microwave applicators. It is especially useful for applications where a certain amount of minor arcing in the material being processed can be tolerated, and to provide data to dynamic microwave power management algorithms. May also be suitable for other applications where precise measurement of light is needed.


Key Features

  • High Sensitivity: minimum light detection to 0.01 lux
  • Extremely wide dynamic range up to 167,000 lux.
  • Broad spectral range from 300 nm (UV-A) through visible light to 900 nm (IR-A).
  • Provides instantaneous and integrated light level data
  • Differentiates between minor arcing and major arcs
  • User-defined detection thresholds
  • High-speed relay alarm output for major arc events
  • Ethernet TCP/IP communications
  • Housing integrated to fit Tri-Clamp™ choke tube fittings, installs in minutes


Physical Specifications

  • Size:   125mm L x 85mm W x 45mm D
  • Output Connector:  M12 DIN, eight pin male
  • Control Outputs: Two isolated sets of SPDT relay contacts, 24V @ 1A maximum each
  • Power Supply:  12 VDC at 200 mA, reverse polarity protected
  • Tri-Clamp™ fitting for mounting on 1.5” applicator choke tube
  • IP-67 environmental rating
  • Size:  120mm L x 87mm W x 47mm H



Light is received by a sensitive, wide-spectrum photodiode which is followed by a low-noise amplifier that drives an analog-to-digital converter. The digitized light level data is provided to a high-speed 16-bit microcontroller which analyzes the data, checks for limits, and manages TCP/IP communications with a client computer, which may be a PC or PLC.

In some microwave applications, a certain amount of occasional or low-level arcing within the processed material is expected and tolerated. However, if a strong arc occurs, the microwave system's controls must reduce or stop application of energy to protect the applicator and materials from damage. At any given time, the sensor will be in one of three states:

  • No arcing occurring
  • Minor arcing occurring
  • Major arcing occurring

The sensor is connected to a host computer via an Ethernet TCP/IP connection. An embedded server in the sensor makes limit alarms and light level data available to the host computer. Data available included current light level, average light level and arc counts. Relay contact outputs close in the event of a major arc event for fast response by generator power control or emergency stop systems. A Windows™ utility program is used to configure user settings over Ethernet.


Control Wiring

A standard eight conductor male M12 DIM connector is used for control wiring. Two independent sets of alarm relay contacts are available. The contacts are rated at 24V @ 1 amp maximum.


Pin Number



Relay 1 NC


Relay 1 Common


Relay 1 NO


Relay 2 NO


Relay 2 Common


Relay 2 NC


Power supply input +12 VDC





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