TECHNICAL GUIDE■ Electrical specifications
Terminology - Definitions and Explanations - …… P7-2
Switch series and parallel connection methods … P7-2
・Direct current 2-Line Type・Direct current 3-Line Type

Conditions of use……………………………………… P7-3・Use with AC 100V-200V
・Connecting to a load
・In the case of using a switch with LED

Confirmation of switch operation………………… P7-3

・Dry contact type・Contact-less type・Confirming operation by using resistance・Confirming operation by using voltage

Wiring precautions ……………………………………… P7-4
Precautions of switch connection ………………… P7-4
■ Mechanical specification
Terminology - Definitions and Explanations - …… P7-6
Protective structure …………………………………… P7-7
・IP code
・Waterproofing (Coolant)
・Dustproofing
・Protective cover■ Setting methods
Switch installation and signal setting methods … P7-8
Preliminary installation and off-line settings …… P7-9
■ Common sense of measurement
Basics of measurement ……………………………… P7-10
・Accuracy
・Abbe theory
・Temperature・Shape of contacting part and contact force
・Timing of measurement
・Contacting point

No.AB9-1E

7-1

TECHNICAL GUIDE - Electrical■Electrical specifications Terminology - Definitions and Explanations Output modeThis refers to the type of signal output from switching part. There are two types of signals as indicated below.
(1) Normally open NO(2) Normally close NC

How to selectCharacteristics of normally open (NO) type・ All types have pretravel (the distance it needs to be pressed to
output the signals), and in the case of dry contact types, there is no
occurrence of chattering since the switching part is normally open.
・ NPN open collector output types can be easily connected toprogrammable controllers (PLC), sequencers and CNC.

Characteristics of normally close (NC) type・ Types with and without pretravel are available. In case of dry
contact types, since the switching part is normally closed, chattering
may occur due to vibrations (mainly in cases of low contact force).
・ Normally close circuits are failsafe (any input errors are notified
immediately). The use of this interlock system makes it possible todiagnose malfunctions such as cable disconnections and signaltransmission problems.

Inversion (Level Conversion) method: NO→NC,NC→NO
Electrical:

・By connecting an I/F unit to either the NO type or NC type, theoutput of the I/F unit can be inverted (NO→NC, NC→NO).
・NC types converted from an NO type by an I/F unit are no longer
failsafe.

Mechanical:

Inversion is possible depending on the installation method.

・By initially pushing in the free position.
・Inverted by means of a lever.

Open collector
The output terminal of this transistor circuit is the collector of the transistor (see diagram below).

NPN transistor output (Open collector)

Since circuits using an NPN transistor absorb the load current(in the manner of a sink), the load is connected between a power
supply having a potential higher than ground and the collector.

Since circuits using a PNP transistor discharge the load current(in the manner of a source), the load is connected between the circuit
ground and the collector.
Main circuit

Load

OutputLoad

Main circuit

Output・NPN transistors are commonlyused transistor. Connections canbe directly made to a
programmable controller orcounter.
・These are popular in Japan andthe US in the form that absorbs
current (sink type).

PNP transistor output (Open collector)

・These are incorporated primarily
in devices exported to overseas
destinations such as Europe.
・These are in the form thatdischarges current (sourcetype).

Types of loads
Resistance loads (Expressed in the output rating)・These mainly refer to loads in the form of resistors.
・These loads make it difficult for large current to flow when thecircuit is switched on and off, and the current that flows to thecircuit can essentially be calculated using the following equation:
Current value = voltage value ÷ resistance value

Inductive loads
・ These primarily refer to relay coils, motors and solenoids.
・ Load can be used only when the driving current of these loads iswithin the switch contact rating. When the switch is turned off,counter electromotive force is generated and will require a diode orsurge absorbing element to be connected in parallel to absorb this.
Load

Vcc

e.g.) Relay driven (Use a relay of which driving
coil current 15mA or less)■Switch series and parallel connection methods
Direct current 2-line type
Series connection (AND)When the connected switch is on, the load
voltage VRL is defined as VRL = Vcc-n x 3(V), caution is required with respect todefective load operation.

Load

Parallel connection (OR)Load

Wiring precautions:

Vcc: Power supply voltage 24V (max)n: No. of switches
3 (V): Switch drive voltage
V: Vcc-VRL
When the connected switch is off, theleakage current IRC flowing to the load isdefined as IRC = n x 0.8 (mA), caution isrequired with respect to defective load
return.
There is no limit in the number that can beconnected in the case of contact switch(no LED or built-in interface unit)

7-2

No.AB9-1E

Direct current 3-line type
Series connection (AND)Load

Parallel connection (OR)Load

Wiring precautions:
The number of connected switches
must be within the range that satisfies
the following relationship:
IL + (n-1) Xi ≦ Upper limit of switch
control output*
10mA (max) in case of non-contact
switches.
In case of using an AND/OR connection,
since there may be cases in which thistype of connection cannot be used due
to erroneous signals or leakage current,
please confirm the absence of suchproblems before using.

TECHNICAL GUIDE - Electrical■Conditions of use
Please use dry contact types at a voltage and current within the contact rating.
Use with AC 100V-200V

Effect on accuracy due to electrical delay

・These switches cannot be directly controlled with AC 100-200V.
・Please refer the diagrams below in the case of desiring to operate asolenoid valve or AC 100V relay with the switch signal in theabsence of a DC power supply within the device.

・If there is a difference in the sampling times of the switch signal andpositioning data, large variations occur in repetitive accuracy whenthe measuring speed is increased.

A DC power supply (DC 24V,
approx. 0.2 A) is provided andthe switch and interface unit
(CL-1F) are used to operate thevalve and relay.

・Do not attempt to drive an inductive load directly with theseswitches. Direct driving can damage the switching parts andsemiconductors of the internal circuitry.
・In case of driving an inductive load, connect a surge absorber inparallel with the load, and connect an external load such as a relay
or transistor allowing an adequate flow of current for load driving.

CL-1F

Load
Load

DC 24Vpower supply

CL-1F

AC - IN

In case of using a switch with LED
Load
Load

Interface unit (Refer to P2-2)

AC100V〜200V

Connecting to a load

AC100V〜200V

DC 24V,AC adapter
AC outlet

・The LED can be damaged if the switch is connected directly to thepower supply (DC 24V). In case of using a sequencer, a resistor is
not required if the outflow current of the sequencer is about 7mA.

×

24V
power supply

Sequencer
Current

Current

Use with micro load
Use the switch within the range of DC 24 V, 0.2 mA to 10 mA (max.)■Confirmation of switch operation
Dry contact typeNon-contact type・Connect the switch in the manner shown in the diagram below.
・Limit the LED forward current to about 10mA by inserting a resistor.
・Resistance value = (power supply voltage - LED forward voltage) ÷current = (24-2) ÷ 0.01 = 2KΩ The LED forward voltage is about 2V.
・The resistor may be installed on the DC 24V or 0V side.
・The LED glows when the circuit is closed. Switch operation is normal.
・ In case of using a sequencer, a resistor is not required if the outflow
current of the sequencer is about 7mA.
・Operation might not be properly confirmed using a digital test
(multi-meter)

・Connect the switch in the manner shown in the diagram below.
・Please note that output circuit will be damaged by over current,
when switch output under NPN output form is directly connected to+24V or when switch output under PNP output form is directly
connected to 0V.
・Please insert resistor with resistance around 3kΩ so that a current of
about 10mA will flow
(1) between +24V and output in case of NPN output type,(2) between 0V and output in case of PNP output type, in the output circuit.
・In case of using a sequencer, a resistor is not required when theoutflow current of the sequencer is about 7mA.
NPN Output
Brown

24 V
power supply

3Black(output)

24V
power supply

Blue

Current
PNP Output
Brown
Black(output)

24V
power supplyBlue
3

Confirming operation by using resistanceConfirming operation by using voltage

・Set the tester to a resistance range of x 10, and connect the minus
lead of the tester to the switch output (brown), and connect the plus
lead of the tester to the switch 0V (blue).
・The deflection of the tester needle indicates around 0W when theswitch plunger is pushed in and roughly infinity (•) when switch tip isreturned.
・For switches with LED, note that the tester may not swing.

・Set the tester to a voltage range of 50V and measure the voltage
between the switch output (black) and 0V (blue).
・For NPN output type, when the tip of the switch is pressed,
the indicator of the tester changes from 24V down close to 0V.
・For PNP output type, when the tip of the switch is pressed,
the indicator of the tester changes from 0V up close to 24V.

No.AB9-1E

7-3

TECHNICAL GUIDE - Electrical■Wiring precautions
Cables・ Do not subject cabtyre cables or core wire cables toexcessive pulling or twisting of 30N or more.
The bending radius should be at least R7.
(Except for heat resistance cable)
・ In case of attaching an extension to cables of theseswitches, since there is greater susceptibility toincreased residual voltage, waveform distortion and induction due tothe effects of wire resistance and inter-wire capacitance, try to use
the shortest length possible.
Furthermore, please use a cabtyre cable having a cross-sectional
area of 0.3mm2 or more.

・Since operating errors may occur due to induction when high-voltage
lines or power lines are wired within the same conduit or duct asswitch wires, wire them in separate ducts.
・Cabtyre cables are used as robot cables without any safetycompromise since the working voltage and current are low, thoughcabtyre cables are not applicable to UL, CSA, En or other safety
standards.
・Use a molding when waterproofing is required so that there are no
exposed portions of the terminals.
・Please use a wire braid or protective tube in harsh environments
where cuttings may be generated.

■Precautions for switch connection
Always make sure to turn off the power before installing or removing switches.
This is to prevent damage to the device caused by improper wiring or short-circuits of output lines.
Application of an excessive voltage or application of an alternating
current power supply (AC 24 V or higher) to sensors using a direct
current power supply has the risk of damaging the switch.

Brown

Brown
SwitchNG (×)
Blue

Switch

Black
Blue

Load

Either ground the switch with a switching power supply in close
proximity to the switch or ground through a capacitor (approx.
0.1-0.47 µF) for the purpose of lowering the impedance of the framein order to increase the resistance to entrance of induction noise by
servo drivers or similar devices.

Voltage of +24 Vor higher (×)
Load

+V
FG

Switch0V

GND(0.1-0.47µF)

Alternatively, attach a ferrite core to the switch cable.

SwitchLevel conversion,etc.
Ferrite core

7-4

No.AB9-1E

NOTE

www.metrol.co.jp/en

No.AB9-1E

7-5

TECHNICAL GUIDE - Mechanical■Mechanical specification Terminology - Definitions and Explanations Signal point (Operating point)

Movement differential MD

Position Where a Signal is generated

Amount of movement until signal is inverted after returningfrom signal point

・Although this is normally indicated with pretravel, it may also be
expressed as the distance from the stopper surface in case of
stopper bolt switches.
・Since it is easier to make a judgment on the signal point based on
the contacting part position and this does not vary according to theconditions of use or type of contact used, position and accuracy
can be clearly indicated.
Workpiece
Position where signal is output
Pretravel (Distance up to signal point)

Pretravel PT (Distance up to signal point)
Amount of plunger movement from free position to signal
point

・In the following explanation, amount refers to a distance or angle(units, mm or degrees).
・ There is always pretravel in case of normally open (NO) switches.
・ Pretravel is nearly 0 in case of normally closed (NC) switches.
・In addition, there is pretravel even in normally closed (NC) switches
in case of having an intermediate shaft. Pretravel is normally about
0.2 to 0.4mm.

Overtravel OT (Movement after signal point)
Amount of movement from signal point to operating limit
position・The greater the amount of overtravel, the less chance of colliding
and causing a malfunction. This can be made large for all contact
type switches.
・When using the switch the plunger is normally pressed and released
in operation, OT becomes PT and normally open output mode isconverted to normally close.

Stroke TT (Overall movement : Total travel)
Amount of movement by the contacting part from free
position to operating limit position

・ This is the sum of pretravel and overtravel

Workpiece
Range of contacting
part movement
StrokeThis region is an undetected area. METROL contact switches withdry contact for switching part don't have movement differential.
Movement differential occurs for any types of electrical switches,
including limit switches, micro switches, proximity sensors andoptical sensors.
・Since the signal is not inverted unless the contacting surface returns
by greater than the amount of the movement differential in case ofusing in such a manner that the contacting surface returns
immediately after operating, thickness less than the movement
differential as shown in the diagram cannot be discriminated.
・Therefore pretravel greater than or equal to the movement
differential is required in case of non-contact devices.
Signal point

Returnsignal point

Detected object

Contacting part
Free position

In addition to the switch itself, the amount of deflection of a retaining
portion (support column) may be added due to the contact force.
Hysteresis does not result in error if signals operating from the same
direction at all times are obtained.
Please pay attention that it is different from hysteresis.

Repetitive accuracy
The detected object is pressed from the vertical direction
towards the contacting part of the switch. The difference
between the maximum value and minimum value obtained
from the variation in the signal point (dimensions) whenpushed in 20 times or more is represented with the range (R)(defined by METROL).
・ The limit of reliability is ±R
・ In case of automatic measurement, judgments are typically madeon the basis of a single measurement.
・ However, values cannot be clearly indicated with average values
and standard deviation alone (the σ value is displayed lower than
the actual value). The use of R is the strictest means of representing
accuracy.
workpiece

No.AB9-1E

Inversion
signal point

This refers to a difference in the operating point when thecontacting part has returned after being pushed beyond theoperating position.

ON
ON

Error in operating point during
repeated operation
Error

Temperature drift (Temperature characteristics)
This indicates the amount of fluctuation in the operating
position caused by fluctuations in parameters of anelectronic component corresponding to a change in theworking temperature.

・ It represents the maximum fluctuation in the operating distance overa temperature range of 10 to 40°C.
・ Temperature drift occurs due to fluctuations in the switching part ofelectronic components caused by changes in temperature, andoccurs in non-contact switches.
・ Furthermore, it is necessary to additionally take physical thermal
expansion of the attachment into consideration .

Contacting part
This refers to the portion of the switch that contacts a
detected object.

・Contacting part is also referred to as a probe.

7-6

Hysteresis*

Pretravel correction

Amount of force required for the contacting part to movefrom free position to signal point (Units : N)

Workpiece
Contact force (N) :Force required for operation

Signal point

Note : Hysteresis (Return Difference)Contact force
・ In case of contact switches with dry contact for switching part, thecontact force is the sum of the spring force required to make themoving parts to reliably return and the spring force required for the dry
contacts to make a stable connection. The contact force is normally
about 1N.
・ Furthermore, contact force may be indicated in terms of return force.
This is for prevention of defective return of the plunger.
And the frictional force of the shaft is subtracted from the spring force.
・ In case of non-contact types, since the switching parts do not requirecontact force to operate, it can be reduced to about 0.1N.
・ In lever types, the contact force is reduced due to the lever ratio.
・ Since contact force may vary depending on the orientation at the timeof use in cases in which the moving parts are heavy, check the returncontact force under the conditions of use (particularly in casereplaceable contacting parts have been fabricated by the user).
・ In addition, pay attention to bracket rigidity in case of types having alarge contact force.

Movement differential

TECHNICAL GUIDE - Mechanical■Protective structure
IP CodeProtective structure refers to the level of dust resistance and moisture resistance.
All products in this catalog are indicated with characteristic numbers in the form of an IP code based on IEC 529:1989 (Degrees ofProtection Provided by Enclosures).

IP 6 7( International Protection )First characteristic number (0-6) : Penetration of extraneous solid objects.
Second characteristic number (0-8) : Penetration of moisture accompanying detrimental effects.
NumberIntrusion of Extraneous Solid Objects

Intrusion of Moisture Accompanying Detrimental Effects

0

Unprotected

Unprotected

1

Protected against extraneous solid objects
50mm or more in diameter

Protected against vertically dripping water2

Protected against extraneous solid objects
12.5mm or more in diameter

Protected against dripping water at an angle of within 15 degrees of vertical3

Protected against extraneous solid objects
2.5mm or more in diameter

Protected against spraying water

4

Protected against extraneous solid objects
1.0mm or more in diameter

Protected against splashing water5

Dustproof: No intrusion of an amount of dust
Protected against pressurized water from any directionthat impairs enclosure operation

6

Dust-resistant: No intrusion of dust

Protected against jetted pressurized water from any direction (high pressure)7

No intrusion of water in an amount that causes detrimental effects even with respect
to temporary penetration

8

No intrusion of water in an amount that causes detrimental effects when continuously
immersed in water under strict conditions determined by relevant authorities

Waterproofing (Coolant)

Protective cover

The water-resistant performance of this standard refers towater. However, the following measures are adopted sincecoolant and cutting oil are commonly used for machine tools.

Protective cover are for preventing damage to rubber boots
and impairment of water-resistance or dustproofing causedby metal fragments and other cutting.
Please select the shape of the rubber boot protective
covering while considering the favtors indicated below.

・Rubber materials used in some products (boots, O-rings) provide
protection against water-soluble coolants and alkaline liquids.
・When covering of cables are broken, liquids penetrates into thecable due to the capillarity action, causing short circuits and contact
failure. Attach protective blades for cables when cables might bedamaged due to chips. (Refer to P2-10.)・Install rubber boot and O-rings after disassembly so that sealing canbe kept. Whenever they are damaged, replace them by a new one.
Apply seal locking agent to the screw threads.
・When there is a risk of damage to the cable by cuttings and so on,please attach a protective braid to the cable. (Refer to P.2-6)
・Please make sure that the sealing properties of rubber boots andO-rings are maintained when assembling disassembled rubberboots and O-rings. Replace any boots or O-rings if they have beendamaged. Apply a sealing thread-lock to all threads.
・When making a connection to extend the cable, use a molding sothat there are no exposed portions when the end of the cable isconnected to a terminal.
・Please note that adhesive and sealants may be eroded by coolant.

・Choose the shape of protective covers (U type, U2 type, and D type)
in consideration of mounting direction, the direction of coolant or air
blower, and the gap.
・When there is no risk of damage to the rubber boots as in the caseof plastic or wood cutting of grindings, it may be better to rinse offsuch debris with coolant or blow it off with blowing air, without
attaching a protective cover.
・An extra cover is recommended to avoid direct hit by high-pressure
coolant or heavy cuttings.

U type (Upward type)Gap
No GapGap

Dustproofing
Air blowing is effective for removing dust, cuttings or coolant
adhered to the contacting surface depending on the type ofadhered debris. However, the following measures are
required for highly viscous substances that can not be
removed by blowing with air.
・Provide boot protectors (option) if the rubber boot might bedamaged due to chips
・Provide automatic opening and closing covers (especially when
operating without operators).
・If a protective cover is still insufficient, provide a separate protector
against chips.
・Provide a separate cover if high pressure coolants or water stream
hit the contact or boot protector.

U2 type (Upward type)

D type (Downward type)

Gap

・In the case of using a bootprotective cover when installedhorizontally (see diagram atright), provide a cover and so
Gapon so that cuttings to notaccumulate in the switch body.

Metalcutting

No.AB9-1E

7-7

TECHNICAL GUIDE - Setting methods■Switch installation and signal setting methods
The methods used to install switches and set the signal operating points vary depending on the purpose inwhich the switch is to be used.
1. Classification according to purpose
1) Setting the signal point as the origin or reference point.
There is no particular need to set an operating point if the signal
output at the position where the contact switch is to be installed,
is the origin or reference point.
The following points are selecting factors of the contact switches.
・ High repetitive accuracy
・No influence by external environment (e.g. Drifts caused by power
supply voltage, temperature, intensity of light, magnetic field, etc.)
・ Small movement differential and hysteresis
・ No restriction on the materials and shapes of detected objects.
As the switches with an amplifier magnify not only the accuracy but
also the fluctuation and drifts, there are the cases where theseswitches are not suitable for use in such a harsh environment.

2) Applications involving making a judgment of pass or
failure using a defined position or dimension as a limiting
criterion.
These applications require heightened setting accuracy of signal
points. Generally, the following 2 types of setting errors are known.
・ Type 1 Errors
misjudging good products as defective ones.
・ Type 2 Errors
misjudging defective products as good ones.

Trying not to commit the type 2 errors is important since the setting
errors of the signal point, to some extent, are unavoidable.
When the application only needs existence detection and doesn't
require high position accuracy, there still is the same idea applying to
the settings of pass/ fail border.

2. Important factors regarding installation methods andsignal setting methods when accuracy is required
1) Ease of making fine adjustments

・ The direction of adjustment of the switch body should be coaxial.
・In case of split clamping, there should be no engagement or screw
rattle in the semi-clamped state, and movement should be smooth.

2) No occurrence of position shifting when locked

・ The locking position should be near the core.
・ There should be no application of thrust in the axial direction duringlocking.

3) Adopting preliminary installation and off-line settings(Refer to P7-9)

3. Installation using a switch bracket and adjusting signal operating point
Installation and setting using a switch bracket

A

BracketNut

Switch outline: Threaded
Bracket: Large clearance(straight hole)

B

BracketNut

Switch outline: Threaded
Bracket: TappedC

Set screw

Switch outline: Non-threaded (h7)
Bracket: Small clearance (H7)

Switch outline: Non-threaded (h7)
Bracket: Small clearance (H7)
Split clamping

Adjustable contacting partNut(threaded)

Setting by the adjustablecontacting part
(Refer to P2-7)

Detected
objectFine adjustment

F

Lock nut

Setting by the anvil of detected
objects such as moving tables.
(Not available when the detected
object is workpiece.)

7-8

Switch fixing methods

・Alternatively tighten the 2 nuts and set and fix theswitch・Not suitable for accurate positioning.
・Suitable for existence detection

The switch is locked in. Position
shifting occurs during setting.
Note that the rigidity ofcommercially produced brackets.

・Screw in and out the switch for position setting.
・Accurate position setting is available(Fine thread is recommended)
・Do not twist the cables

The switch is locked in position
with 1 or 2 nuts.
Position shifting may occur
during setting.

・Set the position of the switch by fingers.
・Accurate position setting is available

There is limitation for tightening
strength.Malfunction may occur
due to excessive force applied to
the fastening part. Whenusing a frame, there is lesspossibility of deformation.

Fixing attachment

DE

Signal setting methods and characteristics

Anvil
Sensor

Detected
objectNo.AB9-1E

Adjusting screw

・Setting the position in the semi-clamped state.
・Most accurate setting is available.

No occurrence of position

・ No need for position setting.
Suitable to inline adjustment.
・ Combinations with A-F are available.

The switch is locked in theposition with the nut.

1) Turn the threaded contacting part or anvil up to
the signal point.
2) Make a half-turn backward and fix it by the nut.
3) Next, slightly loosen the nut and then fasten in
the signal output position by turning the anvil
when there is no play in the screw. Lock inposition by tightening the nut.

shifting when fastening theswitch.

TECHNICAL GUIDE - Setting methods■Benefit of preliminary installation and offline settings
1. Accuracy improvement of signal point (signal setting by using dial gauges or micrometers).
2. Save a great deal of time for setups and changeover of machines. (Improvement in availability ratio of the machine andcut-down of maintenance time.)
3. Reduction of on-line setups, adjustment, and assembly.
4. Cut down the Mean Time To Failure. (MTTF)
5. As the repair work is simplified, skilled technician is not required. (No visit to customers, Cut down on maintenance cost)■Preliminary installation and offline settings
1. Preliminary installation and setting for 1-signal type switches・Preliminary adjustment of the signal point refers to installing theflange, bracket and other parts on the switch outside the machineand setting to the predetermined dimensions so as to eliminate orminimize adjustments within the machine.
・In case of contact switches, the signal is output at a fixed position
from the switch body. Thus, if the installation reference surface is
set in advance for the switch outside the machine, and the distancefrom the operating point is set to the predetermined dimensions
indicated in the design, position adjustment is not required to be
performed inside the machine.
・Unlike non-contact switches, contact switches are not affected by
the surrounding environment, such as the material, shape orbrightness of the detecting body or magnetic fields.
(Refer to P7-8 for signal setting method)

Installation reference surface
Slit types of commercially available split clamping brackets are
frequently produced for the purpose of powerfully tightening balls
and so on, and caution is required since there are many that are notsuitable for switch inching and adjustment. Additional machining isrequired in such cases.

Weaken(thickness of about 1 to 2mm)
Varies according tomaterial and width
Cutout(additional machining ofcommercially available product)

In case of using the switch with a non-threaded switch case.
Completion drawing
Straight hole
Split clamping
bracket

Straight

Slightly move the switch
and fix it in position by split
clamping when the lamp lights

Use a dial gauge
and height gauge

Can be grabbed easily
Press down
Signal check(see diagram at right)

BracketInstallationreference surface

Drawing
dimensions

Lamp

V block
Measured value

Example of bracket(Battery)Drawing dimensions

In case of using the switch with a threaded switch case.
Completion drawing of preliminary installation and setting
Bracket(flange)

Hexagon nut for locking

Installationreference surface

Example of bracket

Alligator clip

V block

Drawing dimensions

Block
gauge

Block gauge dimension =Signal checker(measured value) -(drawing dimension)

2. Preliminary installation and setting for multi-signal type switches
Compatible products
CS-Touch Switch CSC (Refer to P4-21)
・This is effective in cases of a switch unit containing two or moreinternal switches.
・In such cases, The following two tasks are always required:(i) Setting the interval (tolerance) between points(ii) Adjusting the signal points within the machine with a master.
・Although a small signal setting screw is provided for setting thesignal points, there are cases in which this work may not be easy inmachines having limited space.
First, preliminarily set the interval between signal points.
Next, install the bracket on the switch unit according to the design
dimensions. As a result, since these preparations eliminate all
adjustment performed within the machine, corrections can also bemade simply by inching the switch head for either one of signal points.

Preliminary installation and offline setting hardware
This hardware using a microhead was made available for thispreliminary installation and offline setting.
The signal interval can be set in cases when not using a bracket.

Microhead
CSC
The setting hardware is not provided.

Please consult us if you like us to send you drawings for
production.

No.AB9-1E

7-9

TECHNICAL GUIDE Basics of mesurement■Basics of measurement
Generally speaking, dimensional measuring instruments, having a built-in scale, not only convert values of displacement toelectrical quantity or light intensity, but also amplify, calculate, and record the value. These instruments output signals as
threshold values. The price for the instruments is relatively high because an amplifier is required.
On the other hand, METROL contact switches don't require the built-in scale, and output accurate signals as limit values from abuilt-in switching part.
Except off-line use, there are the cases, mostly in machines, where general instruments are only required to output signals as
limit values. In that case, METROL contact switches can show a great cost-effectiveness replacing those expensive instruments.
Since the basic knowledge of measurement is required to make full use of METROL contact switches, refer to the following foryour information.

1. Accuracy

2. Abbe theory

Accuracy consists of "Precision" and "Correctness".
The fluctuation range of numerical values obtained from multiple
measurements is called "Precision", and the difference between
the obtained values and true values is called "Correctness".

A detected object and a standard scale need to be arrangedon the same axis to heighten measurement accuracy.
That is known as Abbe theory. Close to our hand for example,
this theory applies to micrometers but doesn't apply to slide
calipers.

Fig.1

Fig.3

Micrometer

Fig.4

Slide caliper

True value(Master value)

True value

Scale
Both correctness and precision are high.

Precision is high, but correctness is low.

Stand off
Play of sliding part may
cause errors.

True value
True value

Correctness is high, but precision is low.

Both correctness and precision are low.

There is the practice of indicating "Precision" as "Averagevalue", "Deviation value" or "Range" by taking operating point
signals output from the measuring instruments such as digital
micrometers or NC scales, etc. measuring displacement ofdetected objects

When using a switch, offset touch, as shown below, is notrecommended. This can also apply to fine position setting
methods. Offset touch is subjected to rattle of sliding part, loss of
perpendicularity, and deflection of the holder.
Consequently, the way in which the highest accuracy can beobtained by using cylindrical type switch is to locate the plungerof the switch on the same axis as the measuring direction andslide the switch on the same axis for precise position setting.
Fig.5
Signaltransmission part
Detected
objectPlunger

Fig.2
OriginReadout
valuesOriginR
Fluctuation

Frequency(Constant temperature)

Switch case

Offset touch

SwitchIn addition, accidentally applying sideways tightening force to theplunger may cause errors.
(e.g.Split clamping, Set screws)
Fig.6
Lock nut or
Split clamping

Readout
valuesOriginChanging gradually is called "Drift".

Switch7-10No.AB9-1E

SlidingsurfaceTECHNICAL GUIDE Basics of mesurement
3. Temperature

5. Timing of measurement

Instruments and workpiece are subjected to expansion andcontraction according to temperature change.
20°C is standard in industrial standard. The expansion andcontraction cannot be clearly calculated under the condition ofdifferent materials and thermal capacities as well as changes overtime.
Consequently, the following points are important to minimize therisk of expansion and contraction of instruments or workpiece.

Measurement before processing is called Pre-Process
Measurement.
(e.g.Measurement of unprocessed workpiece and parts
dimension before assembly. Detecting process errors fromprevious operation. Upside-down detection of workpiece.)1) Keep the temperature constant.
2) Set the origin by using masterwork whenever a great
temperature change occurs.
3) Select a switch that is least subject to temperature changes.
These attempts results in only minimum compensation required
for use (for example, expansion of high-seed machining spindle).
In that case, a METROL tool setter for machining centers cancompensate thermal expansion of high-speed spindle.
Since there are cases where dimensions realistically affected byflexure (bimetal) greater than expansion and contraction, it may
be more effective to bring coutermeasure for the flexure.
Fig. 7
Heat sourcehKeep it in mind that simple expansion and contraction of iron is
1 µm by 10°C (Brass is 1.9 µm, Aluminum is 2.8 µm).
There are measures as heat sources such as external
temperature, motor, shock absorber, cylinder, high-speed
spindle, coolant, weld, cutting, and body heat, and theirconduction and radiation are also taken into account.
In addition, as constant numbers for elements of electrical parts
vary by temperature change, contact-less type switches with anelectrical circuit in term of amplifier inevitably has temperaturedrift. Refer to section 6, Fig. 8

4. Shape of contacting part and contact force
These two measures are closely related to each other.
And changing the two measures results in instrument errors.
The following points are to be noticed.
・When contacting detected surface, point contact is the best way
to obtain the highest accuracy. But the smaller the dimension ofcontacting point becomes, the larger the contact force can be.
That may cause deformation of either contacting part or
detected surface. (This can be calculated by Hertz equation. But
it doesn't make a big difference in reality).
・Point contact is subjected to plane roughness and friction.
・Large contacting surface may cause errors by deflection due togeometric deformation.
・Since excessive contact force may cause errors by flexure ofswitch holder, commercially produced less-rigid brackets canbe used only for low contact force type switches.
・Flexure (Range of elastic deformation) can be a main factor ofhysteresis and may generate drift.
・Deformation of switch holders can be caused not only due toexcessive contact force but also by excessive force applied
while fixing.
・The contacting force is defined mainly by spring force. But thefrictional force of the plunger should be subtracted from thespring force. Absence of this idea may cause return errors.
・Since non-contact switches (Proximity switches andphotoelectronic switches) detect objects with the detecting
surface and output average values calculated from dimension of
the surface, the values are different from actual measurement
values and actual dimensions. Installing contact type actuators
marks up the total cost and causes loss of accuracy.

Measurement during process is called In-Process
Measurement.
(e.g.During grinding process, measure the work piece dimension
and stop the process when the dimension comes in theallowance. Checking bending radius when the object bent.)
On-line measurement after process is called Post-Process
Measurement.
(e.g.Eliminate defectives after process while giving feedback toprevious process.)

6. Contacting point
In case of contact measurement, accuracy varies according
to how to make the detecting part contact with objects.
1-point measurement method (Thickness measurement)
In Fig. 8 (a)(b), deformation and thermal displacement of the fixing
part, retracting part cause errors.
In Fig. 8 (c), warpage of workpiece, dust and cuttings are error
factors.
Fig. 8 Deflection, thermal displacement(a)(b)
Retracting
mechanism(c)
Fixing part

Stopper
Deformation

h

h

h'

Dust, cuttings,
warpage

Extruding

2-point measurement method
In Fig. 9 (a), making the stopper prop with base level prevent
errors shown in (a)(b) in Fig. 8.
In Fig. 9 (b), errors can be prevented by comparative tolerance
between the masterwork and the detected workpiece. Equivalent
to step measurement.
In Fig. 9 (c), errors caused by dust or warpage can be prevented
by holding the workpiece between 2 points. Plate spring hinge or
bearing is used for the floating mechanism.
Fig. 9Errors may occur due to repeatability of the
movement or temperature change.

(a)

(b)

Retracting by
motor or air cylinder
Stopper ×
Stopperh(c)Masterworkahh

The workpiece is on the base level. Use the base levelas stopper to obtain higher accuracy.

Bearing, Can hold
The floating mechanism is applied so that the it by hand
fixed contacting point touches the workpiece.

3-point measurement method
In Fig. 10 (a)(b)(c), though large diameter or sphere workpiece aremeasured as center-less, magnification ratio drops according to
opening angle. This results in loss of accuracy.
Fig. 10

(a)

(b)

(c)

No.AB9-1E

7-11