sase proximity sensor - ver 2.0
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Kinsetsu Sensa Gijutsu Shiryo
Proximity Sensor Technical InformationVer 2.0 – Jun 2007
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1. What is a Proximity Sensor?
2. Types of Proximity Sensors
3. Classification of Proximity Sensors
4. Inductive Proximity Sensor
4.1 Basic principles
4.2 Features
5. Effects of target objects on sensing distance
6. How to select the appropriate Proximity Sensor?
7. Proximity Sensors Terminology
Content
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A proximity sensor detects the approach of an object without making a contact, making use of changes in a magnetic/electric field.
Spider Web Analogy
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Oscillation
‘Eddy’ Current
Magnetic Field Sensor
Lead Switch
PermanentMagnet
Open/close lead switch by permanent magnet
Open/close element
Sensing object
Changes in capacitance between electrodes and earth
Electromagnetic Field Type
Proximity Sensors make use of (1) Electric Field or (2) Magnetic Field to do detection. Magnetic Field are less commonly used. There are 2 different types of Electric Field: Electromagnetic Field & Electro-static Field.
Electro-static Field Type
Magnetic Field Type
Commonly Used!
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1. By Detection Method
2. By Coil Enclosure
3. By Sensing Head
4. By Sensing Amplifier
5. By Output Mode
6. By Application
3. Classification of Proximity Sensors
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E2EV
E2EY
E2E
E2K-L
Inductive Type
1. By Detection Method
E2K-C
Capacitive Type
3. Classification of Proximity Sensors
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2. By Coil Enclosure
Shorter sensing distance Not affected by surrounding metal
Longer sensing distance Affected by surrounding metal as electromagnetic field flows backward to the sensor
3. Classification of Proximity Sensors
Shielded Type (Flushed-mounted)
Unshielded Type(Non-flushed mounted)
E.g. E2E-X2ME1-M1 E.g. E2E-X5ME1-M1
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3. By Sensing Head
Shape Sensor Face Product Model Applications
Cylindrical Type
PBT E2A
E2E
General purpose
Fluoro-resin E2EQ
E2FQ
Anti-spatter for Automotive
Stainless Steel
E2EH High temp (up to 120C) for Food & Beverage
E2FM Stainless steel housing for harsh environments
Rectangular Type TL-N General purpose
Flat Type E2J
E2C
Flat head for robots or mounting constraint
NEW
3. Classification of Proximity Sensors
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4. By Sensing Amplifier
E2C-T
Amplifier Product Model Advantages
Built-in Amplifier
Easy to use Easy to mount
Separate Amplifier
Compact head for space constraint machines Teaching functions available for more precise detection
In-cable Amplifier
Compact head for space constraint machines
E2C-EDA
E2E TL-N TL-W
NEW
E2EC-QC / E2EC-MC
3. Classification of Proximity Sensors
E2EC
NEW
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DC/AC Output Circuit
with Polarity
without polarity
NO/NC selected by connections
AC/DC
2- W
ire
Typ
e
DC
AC
5. By Output Mode
3. Classification of Proximity Sensors
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DC/AC Output Type Circuit
DC
NPN
NPN Open Collector
PNP
PNP Open Collector
3 -W
ire
Typ
e
3. Classification of Proximity Sensors
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6. By Application
Product Model Application Key features
E2FM
E2FM-Q (Flourine-coating)
Harsh environments where grinding, collision & mechanical collision are highly prone
• 0.8mm thickness SUS303 housing• Chip-immunity function• Chemical and detergent resistance
E2EH-X Food & Beverage, High-temperature wash down areas
• SUS316L housing • Heat resistance up to 120C
E2C-H High-temperature environments
Heat resistance up to 200C
E2E-X-U
E2E-X-U-M1GJ
Machine oil, cutting oil environments
• PUR cable (Frame proof, lead free and halogen free)• Smart click connector (E2E-X-U-M1GJ)
E2AX Petrochemical plants • ATEX Group II CAT 3D cert.• IP65 complied
E2AW Welding plants,
Automotive
• High temp. abrasion-resistant coating on sensing face
E2AU Mobile platforms • Cable breakage resistance• High resistance to cyclic and rapid temperature change
NEW
NEW
NEW
3. Classification of Proximity Sensors
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Application Example
Injection mold closure detection
Plastic injection machines can generate a lot of heat due to energy dissipations from molten materials. In this application, the inductive proximity sensor must be resistant to high temperature.
E2C-H (up to 200C) E2EH (Up to 120 C)
Plastic Injection Machine
Recommendations:
NEW
3. Classification of Proximity Sensors
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LC Amplitude
Detectingcircuit
Outputcircuit
Target Oscillation circuit
High-frequency magnetic field
4.1 Basic Principles of Inductive Proximity Sensor
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Metal object
Approach of object
Sensor
Amplitude of oscillation
Operating level
Output voltage
Switching circuit
Releasing level
Off
ON
Off
4.1 Basic Principles of Inductive Proximity Sensor
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Oscillating circuit
Object (metal)
Sensing coil in the proximity sensor
The detection coil located at the front end of the sensor produces a high-frequency magnetic field as shown in the picture.
When an object (metallic) approaches this magnetic field, an induction current(eddy current) flows in the target due to electromagnetic induction. As the target approaches the sensor, the induction current flow increases, which causes the load on the oscillation circuit to increase. Then, oscillation attenuates or stops. The sensor detects this change in the oscillation status with the amplitude detecting circuit, and outputs a detection signal
The degree of the change in the oscillation amplitude varies depending on the target metal type, and therefore the detecting distance also varies depending on the target metal type
Principle of operation
4.1 Basic Principles of Inductive Proximity Sensor
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Operating principle of all-metal Prox. (E2EV type)
LC Frequency
Comparisoncircuit
Outputcircuit
Target Oscillation circuit
High-frequency magnetic field
Detects all kinds of metal at the same distance. The all-metal type is basically included in the high-frequency oscillation
type. The all-metal type incorporates an oscillation circuit in which energy loss caused by the induction current(eddy current) flowing in the target affects the change of the oscillation frequency. When a target approaches the sensor, the oscillation frequency increases regardless of the metal type. The sensor detects this change and outputs a detection signal.
4.1 Basic Principles of Inductive Proximity Sensor
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Operating principle of non-ferrous metal Prox. (E2CY, E2EY type)
LC Frequency
Comparisoncircuit
Outputcircuit
Target Oscillation circuit
High-frequency magnetic field
The nonferrous-metal type is basically included in the high-frequency oscillation type. The nonferrous-metal type incorporates an oscillation circuit in which energy loss caused by the induction current flowing in the target affects the change of the oscillation frequency. When a nonferrous-metal target such as aluminum or copper approaches the sensor, the oscillation frequency increases. On the other hand, when a ferrous-metal target such as iron approaches the sensor, the oscillation frequency decreases. When the oscillation frequency becomes higher than the reference frequency, the sensor outputs a detection signal.
4.1 Basic Principles of Inductive Proximity Sensor
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1. Non-contact detection
2. Only detect metals
3. Detecting distances are small (0 to 30mm typ.)
4. Can be used in severe environment (e.g. dusty environment)
5. High response speed
6. Compact sensor head for installation flexibility
Iron Copper Brass
4.2 Features of Inductive Proximity Sensor
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1. Material of the object
2. Size of the object
3. Thickness of the object
4. Effects of plating
Factors that affect sensing distance:
5. Effect of Target Object on Sensing Distance
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Steel
SUS
Brass
Aluminum
Copper
100%
70%
40%
30%
28%
1. Material of the object
Of Rated SD
Ferrous
Non-Ferrous
5. Effect of Target Object on Sensing Distance
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The detection distance varies greatly depending on the material of the detecting object
Magnetic material or ferrous metal such as iron, SUS have longer sensing distance, while non magnetic metals or non-ferrous metal have shorter sensing distance
Side length (one side) of sensing object d (mm)
E2E-X1R5E
Sen
sin
g d
ista
nce
X (
mm
)
1. Material of the object
5. Effect of Target Object on Sensing Distance
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Iron
SUS
BrassAluminum
Copper
Conductivity of test object
Sensing distance X mm
The higher the conductivity, lower the magnetic inductance Non ferrous metals are more conductive then ferrous metals. Hence, it offers lower resistance to the eddy current, resulting in that the magnetic field penetrates deep inside the metal Less flux appears out, and hence the sensing distance gets smaller
Sensing distance
Non-ferrous metal, such as Aluminum, Copper
Ferrous metal, such as Iron, SUS
Object
Sensor head
Object
Sensor head
1. Material of the object
5. Effect of Target Object on Sensing Distance
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2. Size of the object
Sensing distance becomes short Stability
Side length(one side)Of sensing object :d(mm)
If the object gets smaller then the standard test object, the detection distance decreases
5. Effect of Target Object on Sensing Distance
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3. Thickness of the object
The thickness of magnetic metal (iron, nickel, SUS etc.) must be 1mm or more.
When the thickness of a non-ferrous metal is 0.01mm or less, it has a detection distance equivalent to that of a target of ferrous metal.
For Aluminum foil with thickness of 10m, the resistance offered to the eddy current would be higher than a 10mm thick aluminum sheet.
The flux cannot penetrate deep inside the foil and will confine mostly on the surface of the object => Hence, longer sensing distance.
Thickness of sensing object : t (mm)
Sen
sin
g d
ista
nce
X (
mm
)
30
30t
Object
Sensor head
10m
5. Effect of Target Object on Sensing Distance
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4. Effects of plating
Thickness and base material of plating type Steel (%) Brass (%)
No Plating 100 100
Zn 5 to 15m 90 to 120 95 to 105
Cd 5 to 15m 100 to 110 95 to 105
Ag 5 to 15m 60 to 90 85 to 100
Cu 10 to 20 m 70 to 90 95 to 105
Cu 5 to 15 m --- 95 to 105
Cu (5 to 15 m) + Ni (10 to 20 m) 70 to 95 ---
Cu (5 to 10 m) + Ni (10m) + Cr (0.3 m) 70 to 95 ---
Note: % is with respect to non-plated detection distance
If the object is plated, the detection distance will be affected.
5. Effect of Target Object on Sensing Distance
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1. Target Materials
- Sensing Object => Determine inductive/capacitive type
- Sensing Distance => Determine barrel size
- Direction of movement of objects
2. Environment
- Presence of metallic chips, sputter or filings?
- Presence of cutting fluids, chemicals, detergents or oil?
- High temperature?
3. Mounting restrictions
- Any installation constraints?
4. Other requirements?
- Output type, shielded/unshielded, separate amplifier & etc…
6. How to select the appropriate Proximity Sensor?
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Parameters Description Product
AC/DC
DC
24 to 240Vdc, 48 to 240Vac 12 to 24Vdc
E2E
E2E other models
Temperature -25 to 70C -10 to 200C 0 to 120C
General
E2C-H, E2C-EM02H
E2EH-X (DC 3-wire)
Body material One piece SUS housing PBT sensor head Teflon coated
E2FM
E2EH-X (most models)
E2FQ
NEW
NEW
6. How to select the appropriate Proximity Sensor?
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Please consider following points while selecting and installing a Prox. Sensor.
Detection object and activation condition of proximity sensor
Specific conditions of
object
Direction of movement of
object
Peripheral metal
Sensing distance
Material, size, shape,
existence of plating, etc.
Transit interval, speed,
existence of vibration, etc.
Material, distance to detector,
orientation, etc.
Permitted deviation
error in transit point, etc.
Detection (setting) distance, shape of sensor detector (square rod type, cylinder type, through-type, slot type). Effect of peripheral metal (shielded type, non-shielded type), response speed (response frequency). Effect of temperature, effect of voltage …
6. How to select the appropriate Proximity Sensor?
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Please consider following points while selecting and installing a Prox. Sensor.
Load
Resistance load – Non-contact control system
Inductance load – relay, solenoid, etc.
• Constant current value, surge current value
• Operation, reset voltage (current)
Lamp load
• Constant current surge
Open/close frequency
Electrical Conditions:
Power Supply
Direct current (voltage change value, current capacity value)
Alternating current (voltage change value, frequency, etc.)
Need for S3D2 controller
Selecting the voltage type
- DC type
- DC type + S3D2 controller
- AC type
6. How to select the appropriate Proximity Sensor?
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Please consider following points while selecting and installing a Prox. Sensor.
Environmental Conditions:
The environment tolerance characteristics of the proximity sensor are better than other models of sensors, however, investigate well before using in harsh temperature conditions or in special atmospheres.
Temperature and humidity
Atmosphere Need for water resistance or oil resistance, need for explosion proof type
Water, oil, iron powder, and other special chemicals
High value or low value, existence of direct sunlight, etc.
Temperature effects, high-temperature use, low temperature use, need for shade, etc.
Vibration and shock
Need for solidarity, mounting method
Size, duration
6. How to select the appropriate Proximity Sensor?
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Please consider following points while selecting and installing a Prox. Sensor.
Environmental Conditions:- Water Resistance
Do not use in water, rain, or outside.
- Ambient Conditions
In order to maintain reliability of operation, do not use outside the specified temperature range or in outdoor conditions. The proximity sensor has a water resistant structure, however, it must be covered to prevent direct contact with water or water-soluble shaving oil. Do not use in atmospheres with chemicals, in particular strong alkaline or acid (nitric acid, chromic acid, or hot concentrated sulfuric acid).
- Explosive atmospheres
Cannot be used in atmospheres where there is a danger of explosion. In this case, it is recommended to use an explosion-proof sensor.
6. How to select the appropriate Proximity Sensor?
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Please consider following points while selecting and installing a Prox. Sensor .
Mounting Conditions:
When deciding the mounting method, take into consideration not only restrictions due to the mechanical device, but also ease of maintenance and inspection, and interference between sensors.
Mounting Procedure
Existence of mounting clamps
Direct mounting
- Secured with bolts or screws
Ease of maintenance and inspection
Mounting spaceFixed location
Wiring method, existence of inductance surges
Wires
- Wire type, length, oil resistance cable
- Shielded cable
- Robot cable, etc.
Conduit cable, duct cable
Direct pull-out, terminal wiring
Ease of maintenance and inspection
Connections
6. How to select the appropriate Proximity Sensor?
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Please consider following points while selecting and installing a Prox. Sensor. .
Effect of external electromagnetic field
- The effect within a direct magnetic field is 20 mT. Do not use a level higher than 20 mT.
- Sudden changes in the direct current magnetic field may cause incorrect operation. Do not use for applications that involve turning the direct current electromagnet on and off.
- Do not place a transceiver near the proximity sensor on its wiring, as this may cause incorrect operation.
6. How to select the appropriate Proximity Sensor?
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Mutual Interference Occurs when more than 2 pieces of sensors are installed facing each other or side by
side, causing the output to be unstable. To avoid interference, it is possible to:
Separate the sensors by a minimum distance. Use one with standard oscillation and the other with different freq. alternately.
Sensor Installation Consideration
Points to note
For E2E-X, min. distance between sensors
6. How to select the appropriate Proximity Sensor?
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Detecting distanceThe distance from the detecting surface of a sensor head to the point where a standard target approaching the sensor head is first detected
7. Proximity Sensor Terminology
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Setting Distance The distance from the reference surface, which allows stable use including the effects of temperature and voltage, to the (standard) test object passage position. This is approximately 70% to 80% of the normal (rated) detection distance.
7. Proximity Sensor Terminology
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HysteresisThe difference between the reset distance and the detecting distance using a standard object. The reset distance refers to the distance from the detecting surface of a sensor head to the point at which the sensor resets for subsequent detection.
7. Proximity Sensor Terminology
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Standard Target A target determined as standard according to the shape , size, and material, that is used to obtain the specification of a sensor.
7. Proximity Sensor Terminology
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Shielded Type The sensing coil is encased in a metal shielding. The magnetic flux is concentrated in front of the sensor because the sides of the sensor coil are covered with metal case. Shielded type is less affected by surrounding metal. And can be embedded in a metal base.
7. Proximity Sensor Terminology
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Non- shielded Type The sensing coil is not metal-shielded. The magnetic flux is spread in front as well all sides of the sensor, as the sensor coil is not covered by any metal case. This type provides a longer detecting distance, compared to a shielded type of the same size.
Since, non-shielded type is easily affected by the surrounding metal, and therefore no object other then the target must be present around the tip of the sensor head.
7. Proximity Sensor Terminology
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Effects of surrounding metal The existence of metal objects other then the detection object near the detection surface of the proximity sensor will affect its detection performance. There could be increase in the activation distance, degrade temperature characteristics, and cause reset failure. Especially while using a non-shielded type as it requires more clearance from the surrounding metal. Provide a minimum distance as advised in the catalog for the particular model. The values in the table are for general guideline only, as it is calculated for the nuts that accompany each model. Changing the nut material will change the effect of peripheral metals.
0
0
7. Proximity Sensor Terminology
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2-wire Proximity Sensors
Point of 2-wire Prox. Sensor(1) Unlike , 3-wire output there is no output cord (black). The output load
is directly connected in series with the sensor. There are two kinds, polarity type and non-polarity type.
(2) Advantage points :(a) Easy wiring(b) In case of many sensors connected in a production machine, if
accidentally, one of the sensor is shorted it is easier to investigate the failed sensor.
7. Proximity Sensor Terminology
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2-wire Proximity Sensors Connection Diagram
Power Supply 24Vdc 1
2
COM
COM
DC24V 6mA
PLC
Common
Input
Sensor
Brwn
Blue
7. Proximity Sensor Terminology
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+ _+ _
Load
Example : In an automobile production line, there were many 3-wire prox. Sensors installed . One of the sensors became short circuited due to sputter from the welding. The power supply that was supplying power to all the sensors tripped. It took them hours to locate the exact the sensor that was short circuited. Because, as soon as the power ON, it will trip, and it is difficult to investigate where the fault location is.
But, if 2-wire Prox. Sensor would have been used, then because of the load resistance, power would not trip. Only, the short circuited sensor would stop functioning. That would then make it easy to locate the faulty sensor.
2-wire type : A real life example
Power Power
7. Proximity Sensor Terminology
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2-wire Proximity Sensors : Caution Points
(1) Surge ProtectionAlthough the proximity sensor has a surge absorption circuit, if there is a device (motor, welder, etc.) that causes large surges near the proximity sensor, insert a surge protector in the source of the surges.
7. Proximity Sensor Terminology
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(2) Residual Voltage : The impedance of the 2-wire type proximity sensor’s circuit, when output is ON, produces a voltage which is the difference of the voltage across the 2 wires connected to it. (V1, 0V). This means that the voltage across the load (V2) is equal to the supply voltage minus V1 (V2=Vs-V1). Make sure that V2 is greater than the operating voltage of the load. (Refer to the characteristic chart “Residual voltage”)
2-wire Proximity Sensors : Caution Points
Proximity Sensor V1
Load
V2 Power Supply
Vs
Load Voltage V2 = Vs – V1
7. Proximity Sensor Terminology
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(2) Leakage current : With a 2-wire proximity sensor, a small amount of current flows (leakage current) to keep the circuit operating even when the sensor is turned OFF. (Refer to the “leakage current characteristic graph” . Because of this current, a low voltage remains on the load, sometimes preventing the load from properly resetting. Before operation, check that the residual voltage is lower than the reset voltage of the load. )
2-wire Proximity Sensors : Caution Points
7. Proximity Sensor Terminology
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When load current is low:When the load current is less than 10mA, connect a bleeder resistor to give the sensor 5mA or more load current. Make sure the residual voltage is less than the reset voltage of the load.
7. Proximity Sensor Terminology
2-wire Proximity Sensors : Caution Points
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2-wire Proximity Sensors : Caution Points
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Response Time
- t1 : The interval from the point when the standard test object moves into the detection range of the sensor to the point when the output turns ON after the sensor activates.
- t2 : The interval from when the standard test object moves out of the sensor detection range to when the sensor output turns OFF.
7. Proximity Sensor Terminology
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Response Frequency
Response Frequency f (Hz) = 1 / (t1 + t2)
- The number of detection repetitions that can be output per seconds when the standard test object is repeatedly brought into proximity.
- See the accompanying diagram for the measuring methods.
7. Proximity Sensor Terminology
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Horizontal detection distance Detection area diagram
How Detection Distance is expressed
In the measurement of detection distance of proximity sensor, the reference position and the direction of approach of the detected object are determined as follow.
Expressed as the measured distance from the reference axis when the standard test object is moved parallel to the reference surface (detection surface).
This distance varies depending on the transit position (distance from the reference surface), thus it can be expressed as an operation point track.
7. Proximity Sensor Terminology
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Perpendicular detection distance
How Detection Distance is expressed
In the measurement of detection distance of proximity sensor, the reference position and the direction of approach of the detected object are determined as follow.
Expressed as the measured distance from the reference surface when the standard test object is made to approach from the radial direction (perpendicular to the detection surface).
7. Proximity Sensor Terminology
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Slot Type
The slot type is frequently used by inserting a thin metal plate through the slot, and thus the insertion distance from the reference surface is measured as shown in the diagram.
7. Proximity Sensor Terminology
How Detection Distance is expressed
In the measurement of detection distance of proximity sensor, the reference position and the direction of approach of the detected object are determined as follow.