Measuring Water Flow Volume Using Reed Sensors - Digi-Key

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]
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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
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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]
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