Current Sensors and Switches Application Note

Current Sensors and Switches

The list of applications for Current Operated Switches and Analog Current Sensors seems endless, limited only by the imagination. These solid-state units are being applied wherever electricity is flowing, for status, feedback, interlocks, alarms, safety, automatic controls and auxiliary contacts.

  1. The single largest application for these sensors is to transmit operational status of motors, lights and air systems back to central computers and PLC's. The energy management systems in new buildings require many such sensors.

  2. An increasing number of air conditioning contractors are using the sensors in lieu of differential pressure and air-flow switches to confirm operational status and detect broken belts. Though the sensors cost more than DP switches, the difference is more than made up by less installation time, shorter wiring runs and much higher reliability.

  3. A pump manufacturer controls the sequencing of backup pumps, using current sensing to indicate increasing load.

  4. A machining company reduced tool breakage by monitoring a rotary indexer for jam-ups resulting from sputtered metal coming from the spot welding operation.

  5. Many panel builders use the units to monitor the integrity of heating elements. A large number of these are in use along the Alaska pipeline. In addition, Ground-Fault Sensors are now required by code in some jurisdictions to monitor unsheathed heating elements.

  6. A major electric tool manufacturer uses the sensors to test the life of flexible cords, noting the drop in current as the strands of wire begin to break.

  7. A water company monitors the output of 3-phase convertors and telemeters the status back to their offices.

  8. In winter, Montana mining operations are crippled if trucks happen to freeze during the night. By monitoring the current in each engine dip-stick heater, the night guard immediately spots burned-out heaters.

  9. A heating system manufacturer uses the sensors to ensure that heaters go off when commanded. Sticking relays were causing the large heaters to burn out.

  10. Sensors automatically start the lubrication system for pumps driven by variable speed drives.

  11. A small machine shop uses a current sensor to drive a counter to count the number of parts cut off by a band saw.

  12. A major fuse manufacturer uses the units to signal the start of test current and the time to fuse rupture in their ongoing test and quality program.

  13. A power company uses the sensors to monitor tower lights, causing automatic switch over to the backup light and auto-alarm when the primary lamp fails.

  14. A machine shop uses a current-operated switch to interlock a surface grinder with its magnetic chuck, preventing operation unless the chuck is energized.

  15. A large communications company uses the sensors to turn on their backup diesel generators automatically whenever their Uninterruptible Power System comes on.

  16. The sensors detect undercurrent in large pumps and initiate shutdown to prevent running while dry.

  17. A machine shop uses a sensor to turn on the shop exhaust system when any one of 8 grinders turns on. Similarly, gas stations are installing sensors which automatically turn on the vacuum system when any of numerous pumps come on-line.

  18. A plastic pipe company uses these sensors to warn operators of plastic grinding machines that a critical overload point is being reached. Since motor rewinding was costing $1500, the sensors were very cost-effective.

  19. A tomato processing in California uses the units to prevent crushers from operating unless the feed conveyors are running.

  20. An Alaska airport uses a current sensor in each hanger for billing purposes. Their central computer monitors the length of time engine dipstick heaters are plugged in.

  21. 104 motors are monitored and status signals are sent back to a central computer controlling nd automating a tomato processing plant.

  22. Several bulk-mail centers use current sensors to detect jam-ups in their high-speed automatic handling machines.

  23. A major electrical appliance company uses the sensors in their manufacturing test line to determine correct current draw.

  24. The U.S. Coast Guard uses these units to signal (1) lamp degradation and (2) lamp failure in ocean buoys and lighthouses.

  25. A manufacturer of hydrogen-burning furnaces uses the sensors to detect burned-out heaters whose purpose is to burn off safely any hydrogen which may escape.

  26. A major power company monitors 7000 HP motors, using current sensors, to note the number of times they turn on, how long they run, and the time between operations as a condition for determining when the motors must be pulled for rewinding.

Advantages of Current-Operated Switches over Differential Pressure Switches

Application: Status indication for fans pumps

  • No piping required

  • No false operation by outside wind conditions

  • Shorter wiring runs

  • No flutter at low flow

  • Greater reliability

  • Immediate delivery from stock

  • No pipe taps, valves, or gages required (Pumps)

  • No V.A.V. fan setup problems

  • Can be mounted in starter enclosure

  • Lower overall cost

  • One standard style fits all installations

  • Five-year unconditional warranty

Data Sheet


Current Sensors and Switches Application Note
Copyright © 2008 Enercorp Instruments Ltd. All rights reserved.