Measuring Water Flow Volume Using Reed Sensors Determine If Filter Needs Replacement Replacement REED RELAYS REED SENSORS REED SWITCHES Introduction There are a multitude of applications that require the measurement of the volume of water. Water filters must measure the amount of water passing through them in order to know when to change the filter. In many cases these filters may be directly connected to the tap water in the home. Also many of the newer refrigerators, also used in the home, are directly connected to a filtered water line. Designers have chosen MEDER’s reed sensors as an inexpensive way to accurately measure the volume of water passing through these filters. Figure 1. MK17-X-3 Sensor physical layout Features • Magnet and Reed Sensor are isolated and have no physical contact by typically having the magnet mounted to a mini paddle wheel, and the Reed Sensor is mounted strategically such that the magnetic field of magnet will be sensed with each rotation of the paddle wheel. Figure 2. Water flows through unclogged filter producing flow measurement with good filter indicator light. • The reed switch used in the Reed Sensors is hermetically sealed and is therefore not sensitive to wet, watery environment • The magnet is not affected by its environment • Tens of millions of reliable operations • Surface mounting and through hole mounting • Cylindrical hole and screw fastening mounting • Contacts dynamically tested Applications • Ideal for sensing the rotation of a paddle wheel in a water filter • Ideal for applications sensing rotation in a host of different configurations Figure 3. Water flows slower through clogged filter producing measurement with replace filter status light. Reed Sensors are the Choice for Measuring the Volume Volume of Water Flowing Through Filters With the potential of ground water pollution on the increase from a host of different sources, many people around the world don’t want to take the chance that their drinking water may have carcinogens or other foul tasting contaminants. An expensive approach is to buy your water in bottled form. Another less expensive approach is to have your water filtered directly in your home. Many people choose the latter approach. With this approach the filters need to be replaced on a regular basis. If this is not done on a timely basis, the filtering becomes ineffective, and may allow the very pollutants one is filtering to begin passing through to the water one drinks. Designers working closely with MEDER’s engineers have solved this problem rather effectively and reliably using reed sensors. MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 1 of 3 www.meder.com Measuring Water Flow Volume Using Reed Sensors Determine If Filter Needs Replacement Replacement REED RELAYS REED SENSORS REED SWITCHES Specifications Defining the MK06 & MK15 Series Operate specs Min Max Units Must close distance 5 25 mm Must open distance 5 25 mm Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact Contact rating Static Contact resistance Dynamic contact resistance Breakdown voltage Operate time Release time Operate Temp MK06 MK06 Storage Temp MK06 Operate Temp MK15 Storage Temp MK15 Typical 50% Min Max Units 200 0.5 1.5 10 150 200 320 -20 -20 -20 -20 0.5 0.1 85 85 130 130 V Amps Amps Watts mΩ mΩ V msec msec °C °C °C °C Usually a tiny magnet 1 mm in diameter and 1 mm long is mounted on the paddle of a small paddle wheel. This paddle wheel rotates whenever water is flowing through the filter. An exact, accurate volume of water is defined with each full rotation of the paddle wheel. The reed sensor senses each full rotation of the paddle wheel and sends that information to an electronic counter. The electronics then keeps track of the volume that has flowed through the filter. Usually a green light on the filter indicate the filter is in good condition, an amber light may light up indicating it is almost time to change the filter. When the red light is on the filter must be replaced immediately. In this manner the water drinkers can satiate themselves with clean clear good tasting drinking water. Because MEDER’s sensors use hermetically sealed reed switches that are further packaged in strong high strength plastic, they can be subject to watery environments without any loss of reliability. The reed sensor is an excellent choice because it can operate reliably over a wide temperature range, and represents an economical way to carry out the sensing function. MEDER’s sensors are packaged for surface mounting as well as through hole mounting. Also, MEDER has cylinder packages as well as screw fastening packages having lead wires for remote attachment to the electronics. Consider some of the below options in surface mount, through hole, cylindrical and rectangular versions for water flow sensors or similar applications. Surface Surface Mount Series Series MK15 MK16 MK17 MK22 MK23MK23-35 MK23MK23-66 MK23MK23-87 Figure 3. MK15 Tape & Reel MK23MK23-90 Dimensions mm W 2.5 H 2.5 L 19.50 W 2.3 H 2.3 L 15.60 W 2.1 H 2.1 L 9.61 W 2.7 H 2.3 L 15.60 W 2.2 H 1.95 L 15.75 W 2.2 H 2.7 L 19.60 W 2.0 H 2.1 L 15.60 W 2.54 H 3.05 L 24.9 Illustration inches 0.098 0.098 0.768 0.091 0.091 0.614 0.083 0.083 0.378 1.060 0.091 0.614 0.087 0.077 0.620 0.087 1.060 0.772 0.079 0.083 0.614 0.100 0.120 0.980 MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 2 of 3 www.meder.com Measuring Water Flow Volume Using Reed Sensors Determine If Filter Needs Replacement Replacement REED RELAYS REED SENSORS REED SWITCHES Through Hole Series Series MK06MK06-4 MK06MK06-5 MK06MK06-6 MK06MK06-7 Dimensions mm W 3.3 H 3.3 L 12.06 W 2.8 H 3.2 L 14.30 W 3.3 H 4.2 L 17.24 W 3.3 H 4.2 L 19.78 Illustration inches 0.130 0.130 0.475 0.110 0.126 0.563 0.130 0.165 0.679 0.130 0.165 0.779 Cylindrical Panel Mount Series Series MK03 MK03 Dimensions mm Dia 5.25 L 25.5 Illustration inches 0.207 1.004 MK14 MK14 Dia L 4 25.5 0.157 1.004 MK18 MK18 Dia L 5 17 0.197 0.669 MK20/1 MK20/1 Dia L 2.72 10 0.107 0.394 Rectangular Screw Flange Mount Series Series MK04 MK05 MK05 MK12 MK12 Dimensions mm W 13.9 H 5.9 L 23.0 W 19.6 H 6.1 L 23.2 W H L 14.9 6.9 32.0 Illustration inches 0.547 0.232 0.906 0.772 0.240 0.913 0.587 0.272 1.260 **Consult the factory for more options not listed above. ** MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 3 of 3 www.meder.com