Automotive Exhaust Fumes Emissions Are Sensed and - Digi-Key

Automotive Exhaust Fumes Emissions Are Sensed and
Controlled By Reed Sensors
REED RELAYS REED SENSORS REED SWITCHES
Introduction
Trying to find a sensor that will function on the underbelly of an automobile
where ice, snow, oil, dirt, grime, very high temperatures and very low
temperatures may exist at any given time represents a very difficult objective.
The muffler system alone may have temperatures on part of its system in the
several hundred degrees C range. Catalytic converters on the muffler system
have a valve that must have its position sensed in order to automatically adjust
the fuel mixture minimizing exhaust fumes. Auto designers have turned to
MEDER’s Reed Sensors.
Figure 1. MK14 Sensor physical layout
Features
• The reed sensors reliably operate between 50˚C to 150˚C
• Magnet and Reed Sensor are isolated and
have no physical contact by typically having the
magnet mounted on the valve in the catalytic
converter and the Reed Sensor mounted and
positioned to accurately pick up the motion of the
valve
Figure 2. Normal amounts of exhaust fumes move through the catalytic converter slightly
moving a valve but not enough to activate the reed sensor.
• The reed switch used in the Reed Sensor is
hermetically sealed and is therefore not sensitive
to rough, wet, oily dirty environments that clearly
exist on the body of the car exposed to the
pavement
• High temperature plastic and Teflon leads used
• The magnet is not affected by its environment
• Tens of millions of reliable operations
• Cylindrical mounting and screw fastening
mounting using high temperature lead wires
• Contacts dynamically tested
Applications
• Ideal for sensing the motion of a catalytic
converter valve in the dirtiest, most temperature
diverse environment on the bottom side of an
auto
Figure 3. Excessive amounts of emissions will move the valve inside the catalytic
converter into proximity with the reed switch sensor activating the electronics.
Reed Sensors Control And Minimize The Exhaust Emissions
In Catalytic Converters
The world is now fully aware that we humans are affecting our planet in a
negative way by adding vast volumes of pollution to the air we breathe. This
has affected the ozone and CO2 levels in our atmosphere. The biggest polluter
has been singled out as coming from the exhaust fumes of our automobiles.
Catalytic converters have been mandated worldwide on all automobiles to
control the gas emissions in the auto exhaust. Following these gas emission
back up into the engine, we find them occurring when air is mixed with the fuel
and ignited by a spark. This produces a mini explosion that drives the pistons,
directly affecting the drive train, in turn moving the car forward. This explosion
can be efficient or inefficient. If it is inefficient, it will use more fuel and increase
exhaust emissions.
MEDER electronic
Application
MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: info@meder.com
MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: salesusa@meder.com
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Automotive Exhaust Fumes Emissions Are Sensed and
Controlled By Reed Sensors
REED RELAYS REED SENSORS REED SWITCHES
Specifications
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 rating
Static
Static Contact
resistance
Dynamic contact
resistance
Breakdown voltage
Operate time
Release time
Operate Temp
Storage Temp
Typical 50%
Min Max Units
200
0.5
1.5
10
150
200
320
0.5
0.1
-50 150
-55 150
V
Amps
Amps
Watts
mΩ
mΩ
V
msec
msec
°C
°
The exact balance of this explosion has many variables: octane level, air
temperature, engine temperature, moisture in the air, etc. Since this is
something that cannot be set at the factory, an adaptable approach that takes
into consideration all the variables must be used. So to further reduce these gas
emissions, auto designers found that sensing the movement of a valve
mounted in the catalytic converter that moves relative to the volume of
emissions can feed back information to make adjustments. This moveable
valve approach in the catalytic converter was chosen because in can take all
the variables into consideration. However, now the problem became how to
detect this movement in such a way to feed back that information to the onboard computer so that adjustments could be made to the air/fuel mixture.
MEDER’s reed sensors were chosen.
Because of the adverse environment the reed sensor needs to operate in, the
hermetically sealed reed switch within the reed sensor is essential.
Furthermore, only very high temperature plastic packaging along with teflon
lead wire can be used. Also, the magnet used on the moveable valve must be a
high temperature Alnico type capable of dealing with temperatures as high as
400˚C. Essentially as the valve shifts its movement the reed sensor will activate
sending a signal back to the on-board computer. It will in turn make adjustments
to the air/fuel mixture, thereby maximizing the burn efficiency, producing
minimal exhaust emission.
The reed sensor is a excellent choice because it can operate reliably from -50˚C
to 150˚C and represents an economical way to carry out the sensing function.
Because MEDER’s sensors use hermetically sealed reed switches that are
further packaged in strong high strength plastic, they can be subject to rough
treatment and environmental concerns such as dirt, grease, and moisture found
on the bottom side of a car.
Consider some of the below options in cylindrical and rectangular versions for
end limit sensor or other similar applications.
Cylindrical Panel Mount Series
Series
MK03
MK03
Dimensions
mm
Dia
5.25
L
25.5
Illustration
inches
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
MEDER electronic
Application
MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: info@meder.com
MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: salesusa@meder.com
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Automotive Exhaust Fumes Emissions Are Sensed and
Controlled By Reed Sensors
REED RELAYS REED SENSORS REED SWITCHES
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
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: info@meder.com
MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: salesusa@meder.com
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