Pulse Counting Type

When an application requires the volume of a fluid, or a distance, or the RPM of a machine tool measured, such an application can be classified as a pulse counting application.
The basic principle of pulse counting is to use a reed switch or a reed sensor on a fixed surface, with a multi-pole ring magnet attached or embedded to the center of the wheel or counter. The best practice is to use ring magnets with two poles for high speed applications and to use ring magnets with 4 or more poles for low speed applications, for better accuracy. When the sensing circuit is low in the range of milli-amperes, the basic reed switch does the job for up to a billion operations.
Reed Switches works so well in such applications as they have a very high operating frequency. The Reed Switches used generate a square wave that can then be translated to the actual consumption of fluid, or energy, or the measurement of wheel speeds. As the wheel rotates, the multi-pole magnet’s alternating North and South poles turn the reed switch on and off continuously and this generates the square wave pulse. This pulse output is used by control circuits to display the actual measurement. The translation of number of pulses to the actual unit of measurement is achieved initially, by conducting various trials. More information regarding magnet actuation of reed switches is available here.
For larger wheels, where the diameter of the magnet is more and the pole moves away far enough to open the reed switch, any standard reed switch with a differential of 40-50% can be used. But for very tiny wheels in water and gas meters, it is important the reed switches with a close differential or 70% minimum differential are used. This is to ensure that the reed switch opens immediately as the magnetic pole moves away, so that the reed switch does not remain closed at any point.
Reed Switches are hermetically sealed, they are immune to dust and moisture, and can safely be used in environments with extreme dirt and moisture. Pulse counting for applications can also be achieved by using active devices like Hall effect sensors, but Reed Switches and Reed Sensors, are passive, have more advantage as no power is consumed for operation, and have no leakage current across the contacts, that need to be compensated for. Some of the pulse counting applications are listed below.
Example Applications
Reed sensor in Surveyor’s Wheels for Measuring Distance
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Surveyor's Wheel A Surveyor's Wheel or a Trundle Wheel, is a device for measuring distance. Each revolution of the wheel measures a
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Nov 7, 2020 |
Sensors for Window Sun-shade Shutter Control
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Shutter Control Application Smart Homes feature automatic sun-shades or blinds as they are also known, which are a movable panels that
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Nov 6, 2020 |
Reed Sensors in Automobile Power windows
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Automobile Power Window These days, most automobile windows can be raised or lowered using buttons near the seats or on the inside of
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Nov 7, 2020 |
Reed sensors to control Automobile Sun-roofs
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Automobile Sun Roof An automotive sun-roof, usually made of tinted glass, is a movable panel that can be opened or closed, fully or
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Nov 7, 2020 |
Reed switches in Petrol and Diesel Pumps
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Fuel Nozzle Petrol and diesel pumping stations are explosive environments where a minor mistake could cause a great big fire. Reed
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Nov 7, 2020 |
Magnet sensors in Bicycle and E-bike Speedometers
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Bicycle Speedometer Fitness is always in, and people who exercise always need feedback on how many calories they have burnt, or how
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Feb 17, 2022 |
Magnet Sensors in Treadmills
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Treadmill Magnet Sensors find a few applications in treadmills for speed and gradient sensing. The speed of the belt is determined by
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Nov 7, 2020 |
Reed Switches and Reed Sensors in Digital Fishing Reels
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Fishing Gear Digital Fishing reels are an improvement over the standard, well-proven fishing reel and rod used for winding and stowing
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Nov 7, 2020 |
Reed sensors for Tamper-proofing Electricity Meters
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Electric Companies use meters calibrated to measure 1 kilo-watt-hour and also measure maximum demand, which is the peak kilo-watt
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Nov 6, 2020 |
Magnet Sensors in Anemometers
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Anemometer An Anemometer is an instrument used to measure wind speed. Spinning cup anemometers are measure wind speeds and are part of
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Nov 6, 2020 |
Flow Meters for checking Lake currents
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Lake Current Meter Underwater currents in lakes and other water bodies are caused by various factors such as pressure gradients due to
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Nov 7, 2020 |
Magnet sensors in Anti-lock braking system (ABS)
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Anti-lock Braking Anti-lock braking system or ABS for short, is a safety system used on aircraft and on vehicles, such as cars,
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Nov 7, 2020 |
Magnet sensors for Automobile Cruise Control
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Cruise Control Cruise Control automatically controls the speed of a motor vehicle by adjusting the accelerator so that the driver need
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Nov 7, 2020 |
Magnet sensors in Satellite dish position sensing in the DTH industry
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Satellite Dish A satellite dish is a concave device used to transmit and receive information and is used primarily in the
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Nov 6, 2020 |
Magnet Sensors in Fluid Metering
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Fluid Meter In most large cities, utility companies or closed communities run piped Water and Liquefied Petroleum Gas, LPG, to all
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Nov 7, 2020 |
Reed switches and Reed sensors in Spirometers
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Spirometer for Lung Function Testing A Lung function test or Pulmonary Function test, PFT for short, is a system to evaluate the
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Nov 6, 2020 |