# Glossary

## Numeric

### 1φ

Category
The name of a state of an electrical signal
Description
Refers to single-phase AC. => See “Single-phase AC.”
Applicable model
NR-HV04

### 3φ

Category
The name of a state of an electrical signal
Description
Refers to three-phase AC. => See “Three-phase AC.”

### 4 to 20 mA output

Category
Electrical circuit
Description
Means that current is output in a range of 4 mA to 20 mA.
This output is widely used as standard analog outputs for instrumentation (plant equipment) and can be easily imported into recorders through voltage conversion. This output is suited for long-distance transmission because it is highly resistant to noise. It also has a high fail-safe characteristic as it drops to 0 mA when a disconnection has occurred.
Applicable model
• NR Series

## A

### A phase

Category
The name of a state of an electrical signal
Description
A type of pulse output from an encoder. => See “Encoder.”

### AC

Category
The name of a state of an electrical signal
Description
Stands for “alternating current,” which refers to electrical signals whose amplitude and direction vary cyclically with time. In terms of power supplies, direct current (DC) is not suited to long-distance power transmission because longer wiring causes voltage drops. On the other hand, AC can efficiently transmit power even over a long distance because the voltage can be raised or dropped freely using a transformer.
Reference
DC
Applicable model
NR-HV04

### AC relay

Category
Electrical component
Description
Generally refers to a type of relay that uses AC (alternate current) for the primary coil voltage.
Sometimes, it also refers to a relay that can open and close AC with the contacts on the secondary side.
Reference
DC relay

### Acceleration

Category
Unit
Description
A physical quantity that expresses a rate of change in speed per unit of time. Its units include “G,” “m/s2 (meters per second per second),” and “Gal” (used for earthquakes).
The following relationship exists between them: 1 G = 9.8 m/s2 = 980 Gal.
An acceleration is generated when the speed changes. The acceleration is “0” no matter whether you sit on a chair in a building or on an airplane that is flying at a constant speed.
Applicable model
NR-CA04

### Acceleration pickup

Category
Sensor
Description
A sensor that detects the acceleration from the vibration of the target object and converts the acceleration into an electrical signal. This sensor is fixed to the target object during use.
A piezoelectric element type and a strain gauge type are available.
Applicable model
NR-CA04

### Alternate current

Category
The name of a state of an electrical signal
Description
=> See “AC.”
Applicable model
NR Series

## B

### B phase

Category
The name of a state of an electrical signal
Description
A type of pulse output from an encoder. => See “Encoder.”

### Bridge box

Category
Sensor
Description
The strain amount is obtained by measuring a minute resistance value. In strain amount measurement, a Wheatstone bridge circuit is used to detect a minute change in the resistance and output it as a voltage change. A bridge box refers to a terminal block that is equipped with this Wheatstone bridge circuit and can support various types of wiring between strain gauges. In terms of strain measurement, this block is sometimes simply called a “bridge,” and a block in a box shape is called a “bridge box.”
Applicable model
NR-ST04

## C

### CAN

Category
Communication standard
Description
A communication method, which is very similar to LAN, developed by the German company Bosch for automobiles. CAN stands for controller area network. If on-board microcomputers (ECUs) are connected through a CAN, digital values (such as rotation speeds) and ON/OFF information are provided for CAN from ECUs. Automobiles are equipped with many electronic controllers to perform control as follows.
• Engine ignition timing control
• Gear box control
• Throttle valve control
• ABS (Anti-lock Braking System)
• ASC (acceleration skid control)
Conventionally, these systems had been used independently. However, as a result of striving for higher performance, it became necessary to develop a mechanism that integrates these systems to enable data communication between them. That is how CAN was developed.
Applicable model
NR-C512

### Capacitor

Category
Electronic component
Description

A component that stores and emits electrical charges. This component emits electrical charges when the voltage decreases. Capacitors are used in various electronic components as follows.

• A component that uses its characteristic to store electrical charges: Super capacitor
• For noise elimination: Bypass capacitor
• For cutting DC components by using its characteristic to prevent further current flow after charges are stored: Coupling capacitor
• Component that uses its characteristic to pass AC components by continuously flowing current until charges are completely stored after the voltage direction changes: Capacitor ground
• Component that uses its characteristic to discharge when the voltage drops to stabilize a power supply: Smoothing capacitor

### Current

Category
Unit
Description
A unit that expresses the amount of electricity flow. Its symbol is “I” and its unit is “A (amperes).” Current flows by being pushed by the pushing power of voltage.
From Ohm’s Law (E = IR), the current that flows when a 1.5 V battery is connected to both ends of a resistor is as follows.
With a resistor of 1 Ω, I = 1.5/1 = 1.5 A
With a resistor of 1 kΩ, I = 1.5/1 k = 0.0015 A = 1.5 mA
The greater the resistance, the less the current.
Outputs for recorders that utilize the magnitude of the current are 4 to 20 mA.
Applicable model
• NR Series

## D

### DC

Category
The name of a state of an electrical signal
Description
Stands for “direct current,” which refers to current whose flow direction (positive/negative) does not vary even if the magnitude changes with time.
For example, 24 VDC means that the waveform shows a straight line at +24 V.
Reference
AC
Applicable model
• NR Series

### DC relay

Category
Electrical component
Description
Refers to a type of relay that uses DC (direct current) for the primary coil voltage.
Reference
AC relay

### Differential input

Category
Electrical circuit
Description
A format of the input circuit of an instrument. This input has the following characteristics.
• Advantage: Less susceptible to noise or potential difference between signal source and instrument GND.
• Disadvantage: The number of measurement channels is half that of the single-end input.
Reference
Single-end input
Applicable model
NR-HA08

### Diode

Category
Electronic component
Description
An electronic component (semiconductor) that passes current only in a fixed direction and is used to control the direction of current.

### Direct current

Category
The name of a state of an electrical signal
Description
=> See “DC.”

### Duty ratio

Category
The name of a state of an electrical signal
Description
Refers to a ratio of a period in which a certain cyclic phenomenon continues.
For example, if the ON time is 1 μs and one ON/OFF cycle is 4 μs, the duty ratio is “0.25” or “25%.”
If the ON time and the OFF time are completely the same, the duty ratio is “0.5” or “50%.”

## E

### Effective electric power

Category
Unit
Description

A type of electric power that can actually be used when the current and voltage phases are misaligned. In the case of AC, the power is maximized when the current and voltage phases are aligned. When the phases are misaligned, there is a lag between the voltage peak and the current peak, making the power smaller. The power that has become unavailable due to this lag is called reactive electric power.

Effective electric power + reactive electric power = apparent electric power

The apparent electric power can be obtained by multiplying the voltage by the current. Because the phases are shifted by capacitors and coils mounted on equipment, devices designed to measure the level of misalignment and correct such misalignment are added to equipment.

### Electric energy

Category
Unit
Description

The total of the electric power used per unit time, which is expressed in units of “Wh (watt hours).”
The magnitude of the electric energy is calculated by multiplying the electric power by the time.

Electric energy (Wh) = electric power (W) × time (h)

For example, a 1-hour use of a 1500 W electric griddle consumes 1500 Wh of electric energy and a 2-hour use of it consumes 3000 Wh of electric energy.

### Electric power

Category
Unit
Description

Refers to how much work electricity does, which is expressed in units of “W (watts).”
Electric power (W) is calculated by multiplying the voltage (E) by the current (I). The higher the voltage and the greater the current, the greater work electricity can do.
The work is expressed as follows using the relational expression of Ohm’s Law (E = I × R).

W = E × I = (I × R) × I = I2 × R

Apparent electric power and effective electric power
There are two types of electric power—apparent electric power and effective electric power (actually available electric power). Although the apparent electric power is always constant, the effective electric power decreases with a phase shift (that worsens the power factor). In other words, the less the phase shift (= the better the power factor), the more the effective electric power. This proves that a device having a large difference between apparent electric power and effective electric power is less efficient and needs to be improved. The unit “VA,” which is often used to express the electric power specifications of an AC device, refers to apparent power, whereas a different unit, “W,” is used for effective power to distinguish the two.

### Encoder

Category
Sensor
Description
A digital sensor that detects the position of the target mechanism.
Encoder types
Classification by the target mechanism
• Rotary encoder: Detects a rotational movement.
• Linear encoder: Detects a linear movement.
Classification by the detection method
• Incremental type: Detects a relative position. Therefore, the position will be lost after the power is turned off. The structure and signal processing are both simple.
In general, “encoders” refer to incremental encoders.
• Absolute type: Detects an absolute position. Therefore, the position will not be lost even after the power is turned off. Thus, the structure and signal processing of this type are complicated.
Detectable items
Rotary encoder
• Current angle: Counts the number of pulses from the origin and converts this number into an angle.
• Angle of movement: Counts the number of pulses during movement between two points and converts this number into an angle.
• Rotation time: Measures the time for movement between two points.
• Number of rotations: Measures the number of rotations per unit of time.
• Rotation speed: Measures the angle of movement per unit of time.
Linear encoder
• Position: Counts the number of pulses from the origin and converts this number into a position.
• Amount of movement: Counts the number of pulses during movement between two points and converts this number into the amount of movement.
• Movement time: Measures the time for movement between two points.
• Movement speed: Measures the distance of movement per unit of time.
Output signals from the incremental type: The relative amount and direction of movement can be confirmed by measuring the A phase and B phase on the basis of the phase difference.
• A phase: A specific number of pulses are output per rotation.
• B phase: Pulses are output one quarter of a pulse cycle behind or ahead of the A-phase pulses.
• Z phase: Only one pulse is output at the origin.
Reference
Rotary encoder

## F

### Four-wire resistance thermometer

Category
Sensor
Description
A type of resistance thermometer that enables the most accurate measurement among resistance thermometers. Two lead wires are extended from each end of a resistor—four lead wires in total.

## G

### Gauge factor

Category
Sensor
Description
A constant that expresses the sensitivity of a strain gauge. This factor shows the shift of the resistance value change of a strain gauge from the theoretical value (“span shift”) in relation to the change in the strain amount. Although the theoretical value is 2.0, an actual strain gauge generally shows a value around 2.
Applicable model
NR-ST04

## I

Category
Sensor
Description
Refers to a non-contact thermometer that measures the amount of infrared light emitted from the target object and converts this amount into a temperature.

### Inrush current

Category
The name of a state of an electrical signal
Description

Refers to a current greater than the rated current that flows for a short period of time immediately after power ON. A large inrush current may cause problems such as those listed below.

• A device is not started with the prepared power supply.
• A fuse blows or a circuit breaker trips.
• The large inrush current becomes a noise source.
Inrush current example
In electrical equipment, a current over the rated one flows immediately after power ON to rapidly charge the smoothing capacitor used in the internal power supply. For example, because an incandescent lamp has a low resistance before it is turned on (when it is cooled down), a current 10 times to 20 times the rated one flows at power ON. “Inrush current” refers to a large current that flows at this time.

### Integrated electric energy

Category
Unit
Description
=> See “Electric energy.”

### Inverter

Category
Electrical component
Description
This component is equipped with a power supply circuit that electrically generates AC power from DC power (inverse conversion). Compared to commercially available AC power supplies, this component enables devices to operate more efficiently because it can optimize the pulse duration, the frequency, etc. according to each device.

## L

### LCR

Category
Electrical circuit
Description
A term that combines “L” for coil inductance, “C” for capacitor capacitance, and “R” for resistor resistance. An “LCR meter” refers to a dedicated electronic instrument that can measure L, C, and R.

### Logic

Category
The name of a state of an electrical signal
Description
Refers to a signal that indicates 0 or 1. The term now also refers to ON/OFF signals. In a computer (CPU), all operations and calculations are handled as binary numbers. “Binary” is a computational method in which the only numbers that exist are “0” and “1.”The numbers we usually use, which consist of a combination of 0 to 9, are called decimal numbers.
A computer uses only “0” and “1” for calculation, but in an actual circuit,
a low voltage state is handled as “0” and a high voltage state is handled as “1.” In general,
a low voltage state is 0 V and
a high voltage state is 5 V.
In this way, “logic signals” generally mean 0 or 5 V ON/OFF voltage signals.

### Low voltage

Category
The name of a state of an electrical signal
Description
Refers to a state where the voltage is low. No specific voltage values have been stipulated for this state.
For the CE marking, ranges from 50 to 1000 VAC and 75 to 1500 VDC are regarded as low voltage.

## N

### N24

Category
Electrical circuit
Description
Means the negative side (0 V) of a 24 VDC power supply. Conversely, “P24” means the positive side (+24 V) of a 24 VDC power supply.

### NPN open collector output

Category
Electrical circuit
Description
An ON/OFF output circuit that uses an electronic component called a transistor. The features of this circuit are its high speed, compact size, and long life because it does not use any mechanical contacts. As a non-contact output for controllers, this circuit is widely used for various purposes, mainly in Japan. In KEYENCE products, this circuit is mainly equipped as a comparator or other control output.
When this output is turned ON, electricity flows from the load via the output terminal (collector) to the COM terminal (emitter). Then, the electricity is converted to a voltage logic signal by the external power supply and load. Generally, 5 V, 12 V, or 24 V is used as an external power supply. The voltage to be measured is shown below.
• Transistor ON: Approximately 0 V (residual voltage)
• Transistor OFF: External power voltage (12 V if the external power supply is 12 V)

### Noise

Category
The name of a state of an electrical signal
Description

Refers to signals unnecessary for device operations and measurements. In general, desired signals are simply called “signals,” while signals that interfere with desired ones are called “noise.” The “S/N ratio” is a value that expresses the signal level in relation to the noise.

Types of noise
• Burst noise
Sudden noise caused by a power source (such as a motor), inverter equipment, contact open/close, lightning, etc.
Due to its large energy, burst noise causes malfunctions and other problems on the affected device.
• Stationary noise
Noise that constantly occurs with a certain magnitude. There is a correspondence between the resolution of a displacement sensor or other instrument and the magnitude of the noise.
Electrical classification of noise
• Common mode noise
As a countermeasure for this noise, a noise cut transformer or a noise filter is attached to the power supply line.
• Normal mode noise
Refers to noise added only on the plus or minus side of the power supply by other equipment.
As a countermeasure, a noise absorbing element consisting of a capacitor and a resistor is attached to the power supply line.

### Number of rotations

Category
Unit
Description
Shows the state of rotation of a shaft used for engines, motors, facilities, OA devices, etc. The word “rotation speed” is also used because this state is expressed as the number of rotations per unit of time. As its units, S-1 is used in the International System of Units (SI), but “rpm (revolutions per minute),” “rps (revolutions per second),” and “rph (revolutions per hour)” are also used.
Calculation example: If 100 pulses are counted per second using an encoder that outputs 10 pulses per rotation, the number of rotations are as follows.
Number of rotations per second = 100 pulses/10 pulses = 10 rotations
Number of rotations per minute = 10 rotations × 60 seconds = 600 rpm = 10 S-1

## O

### Open collector output

Category
Electrical circuit
Description
From a transistor, three wires are extended—E (emitter), C (collector), and B (base). “Open collector” refers to the state where this collector wire is not connected to anything (“open”), and “open collector output” refers to connecting this open collector to a load so as to be used as an output. There are two types of open collector outputs—NPN open collector output and PNP open collector output.
=> See “NPN open collector output” and “PNP open collector output.”

## P

### P24

Category
Electrical circuit
Description
Means the positive side (+24 V) of a 24 VDC power supply. Conversely, “N24” means the negative side (0 V) of a 24 VDC power supply.

### PNP open collector output

Category
Electrical circuit
Description
An ON/OFF output circuit that uses an electronic component called a transistor. The features of this circuit are its high speed, compact size, and long life because it does not use any mechanical contacts. As a non-contact output for controllers, this circuit is widely used for various purposes, mainly overseas.
When this output is turned ON, electricity flows from the COM terminal (emitter) to the load via the output terminal (collector).Then, the electricity is converted to a voltage pulse signal by the external power supply and load. Generally, 5 V, 12 V, or 24 V is used as an external power supply. The voltage to be measured is shown below.
• Transistor OFF: External power voltage (“12 V − residual voltage” if the external power supply is 12 V)
• Transistor ON： 0 V

### Phase difference

Category
The name of a state of an electrical signal
Description
A difference in the phases of two waveforms. For encoders and similar devices, a period shift between A phase and B phase is called a “phase shift,” and the amount of that shift is called the “phase difference.”

### Photocoupler

Category
Electronic component
Description
Insulates an internal circuit from an output circuit to make it harder to transmit noise from an external circuit to inside. A photocoupler consists of a photodiode that emits light when electricity flows and a phototransistor that is turned ON when it receives light. A photocoupler enables electrical noise to be cut off because it conveys ON/OFF through light.

### Piezoelectric element type acceleration pickup

Category
Sensor
Description
A type of acceleration pickup measurement method. A piezoelectric element type and a strain gauge type are available.
=> See “Acceleration pickup.”
Applicable model
NR-CA04

### Pulse

Category
The name of a state of an electrical signal
Description
Refers to a waveform whose amplitude cyclically changes to either the maximum or minimum value. Sometimes, signals that are repeatedly turned ON and OFF are also regarded as pulses.

## R

### RTD

Category
Sensor
Description
Stands for resistance temperature detector, namely, a resistance thermometer.
=> See “Resistance thermometer.”

### Relay

Category
Electrical component
Description
Refers to an electrical component that transmits (relays) ON/OFF signals. A relay passes current through the electromagnetic coil on the primary side (coil side) to convert electrical signals to mechanical movement and turn the contacts (switches) on the secondary side (contact side) ON/OFF.
Reference
AC relay / DC relay / Solid state relay

### Resistance

Category
Unit
Description

(1) Unit of electricity
A unit that expresses how difficult it is for electricity to flow, for which Ω (ohm) is used as the symbol.
From Ohm’s Law (E = IR), the current that flows when a 1.5 V battery is connected to both ends of a resistor is as follows.

With a resistor of 1 Ω, I = 1.5/1 = 1.5 A
With a resistor of 1 kΩ, I = 1.5/1 k = 0.0015 A = 1.5 mA

As shown above, the greater the resistance, the less the current.

Category
Electronic component
Description

(2) Electronic component
A component designed to limit the amount of electricity that flows (electric current), for which “R” is used as the symbol.

### Resistance thermometer

Category
Sensor
Description

A temperature sensor that uses the principle that the electric resistivity of metals varies in proportion to the temperature. Due to its constant resistance changes and large rate of change against the temperature, platinum (Pt) is generally used in resistance thermometers. Other commonly used metals include nickel and copper. A resistance thermometer derives the temperature by passing a certain current (generally 1 mA) through a metallic resistor, measuring the voltage with an instrument, and converting this voltage into a resistance value through Ohm’s Law (E = IR). Three-wire resistance thermometers not affected by the wiring resistance are widely used. Unlike thermocouples, resistance thermometers directly output the measured temperature.

Pt100
A standard for platinum resistance thermometers. “100” indicates that the resistance value is 100 Ω.
Pt1000
In addition to Pt100, there are also other types of commercially available platinum resistance thermometers. Pt1000 is a platinum resistance thermometer having a resistance of 1000 Ω.
Two-wire system, three-wire system, and four-wire system
There are three types of resistance thermometers classified according to the wiring of the lead wires from the resistive element.
• Two-wire system: The measurement accuracy is relatively low because the resistance of the lead wires directly results in errors.
• Three-wire system: The most common system. This system enables accurate measurement by canceling the resistance value of the lead wires.
• Four-wire system: Enables more accurate measurement than the three-wire system.
Specified current
There are also resistance thermometers that have a specified current other than 1 mA. Also note that slight error may occur due to self-heating during use.
Applicable model
• NR-TH08

### Ripple

Category
The name of a state of an electrical signal
Description
Refers to the amount of variation in voltage. For example, if the rated power voltage is described as “24 VDC ripple ±10%,” the output voltage may vary between 21.6 and 26.4 V (24 V ±2.4 V <= 10% of 24 V).

### Rotary encoder

Category
Sensor
Description
This sensor—a type of encoder—is used to check the state of rotation of rotary components such as motors and shafts. This encoder outputs pulses every time the relevant shaft rotates a certain amount. The “resolution” refers to how many pulses are output per rotation and is expressed in units of the “number of pulses/rotation.” There is a wide range of rotary encoders—from inexpensive ones that output 10 to 20 pulses to expensive ones that output up to approximately 5000 pulses. Because pulses are output according to the rotation of the shaft, information such as how many degrees the shaft has moved and how many rotations the shaft has made can be obtained by counting the number of pulses. However, the direction of rotation cannot be determined only with output pulses, so pulses in two phases (A phase and B phase) are output to generate a phase shift so that the direction can be determined.
Reference
Encoder

## S

### SSR

Category
Electrical component
Description
Stands for solid state relay.
=> See “Solid state relay.”

### Servo motor

Category
Electrical component
Description
A motor capable of numerical control. Servo motors are classified into AC servo motors, DC servo motors, etc. and are used for industrial robots, automatic machines, and similar applications. “Servo” refers to a control mechanism designed to operate as instructed. To achieve high-speed, high-precision operation, this motor keeps checking its position on the basis of the output from a built-in encoder and providing feedback to eliminate any deviation from the instructions.

### Single-end input

Category
Electrical circuit
Description
A format of the input circuit of an instrument. This input has the following characteristics.
• Advantage: Easier to increase the number of channels compared to the differential input.
• Disadvantage: Relatively susceptible to noise or potential difference between signal source and instrument GND.
Reference
Differential input
Applicable model
NR-HA08

### Single-phase AC

Category
The name of a state of an electrical signal
Description
Refers to one-system AC. 100 V single-phase AC is supplied from a 100 V household outlet.
Reference
AC / Three-phase AC

### Solid state relay

Category
Electrical component
Description
A non-contact relay that uses semiconductors instead of an electromagnet and contacts on the secondary side (contact side). On the primary side (coil side), an optical semiconductor is used instead of a coil. This relay features high speed and long life compared to relays having contacts.
Reference
AC relay / DC relay / SSR

### Stepping motor

Category
Electrical component
Description
A motor capable of controlling the amount of movement in proportion to a rotation angle through rotation in sync with pulse signals.
This motor allows for accurate positioning thanks to a predetermined stepping amount (rotation angle) per pulse.

### Strain

Category
Unit
Description
Definition of the strain amount
The strain amount refers to the amount of deformation (expansion or contraction) per meter when a load is applied to an object.
For example, if a 2 m round bar is extended by 40 micrometers after being pulled, the strain amount is as follows.
40 micrometers/2 meters = 20 μST (micro strain)
There is no unit for strain because it represents an expansion (contraction) as a ratio. In other words, it is treated as a “unitless” number. However, to indicate that “a given number represents a strain,” “ST” (an abbreviation of strain) or “ε” (because strain is generally represented by the Greek letter ε) is appended after the number. Because strain represents a small value, micro strain is expressed with the prefix “μ” (micro, 1 × 10−6) as in “μST” or “με.”
Difference between dynamic strain and static strain
• Dynamic strain
Rapidly changing strain at a sampling cycle of 1 Hz or higher. Automotive engines and vehicle frames have dynamic strain.
• Static strain
Slowly changing strain at a sampling cycle below 1 Hz. The durability of dams, buildings, etc. is classified as static strain.
Reference
Strain gauge
Applicable model
NR-ST04

### Strain gauge

Category
Sensor
Description

A sensor that measures the strain amount based on the principle that the resistance of a metal changes with its expansion/contraction. With the original resistance as R (Ω), the change in the resistance as ΔR (Ω), and the strain amount as ε, the following relational expression is established.

ΔR / R = constant of proportionality K × ε

In the above expression, the constant of proportionality K is called the “gauge factor,” which has been determined on the basis of the metal (alloy) used for the strain gauge. With no load, the resistance of a strain gauge is generally 120 Ω.

Applicable model
NR-ST04

### Strain gauge-type acceleration pickup

Category
Sensor
Description
=> See “Acceleration pickup.”
Applicable model
NR-ST04

### Strain gauge-type transducer

Category
Sensor
Description

A sensor that converts various physical amounts—including the weight, the force, and the acceleration—to electrical signals using strain gauges as its sensing elements. The types are as follows.

• To measure the weight: Load cell
• To measure the acceleration: Acceleration transducer
• To convert the torque: Torque transducer
• To convert the displacement: Displacement transducer

Four strain gauges are attached to its internal structure and the relevant physical amount is determined on the basis of the strain amount of each (a bridge circuit is built in the transducer). In the case of a load cell, for example, putting a heavy object on it will strain its internal elastic body. The transducer measures the strain amount generated at this time, converts it to a voltage signal, and outputs the signal.

Applicable model
NR-ST04

## T

### TTL

Category
Electrical circuit
Description
A type of logic circuit. This signal turns LO at 0 V and HI at 5 V. This circuit used to be used in electronic circuits to exchange signals.
There are TTL outputs and inputs, and outputs and inputs are paired to transmit signals.
(Stands for “transistor transistor logic.”)

### Tachometer

Category
Sensor
Description
Refers to a rotation speed meter that monitors the number of rotations of the shaft of a machine (such as an engine or a motor) per unit of time. This meter calculates outputs from the “encoder” mounted on the spindle. An automotive tachometer shows the number of rotations of the engine per minute (rpm).
=> See “Number of rotations.”
Reference
Encoder

### Temperature

Category
Unit
Description
A scale that expresses how warm or cold an object is. “°C” is used as its unit. The following types of sensors that can measure the temperature are available.
• Thermocouple
• Resistance thermometer (RTD)
• Thermistor
Applicable model
• NR-TH08

### Thermocouple

Category
Sensor
Description

Refers to the most commonly used type of temperature sensor. Although thermocouples are classified into various types, commonly used types are K, J, E, T, R, S, B, N, and W. Thermocouple types are used selectively according to the operating temperature and atmosphere.

Principle

Thermocouples use the Seebeck effect, a relationship between electricity and heat. This effect describes that when two different metals are connected and a temperature difference is applied to both junctions, voltage is generated between these metals and current flows. This electric power that generates current in a circuit is called thermoelectromotive force and it has been confirmed that its polarity and magnitude are determined only by the materials of the two types of conductors and the temperature difference between both ends.
Using this effect, a thermocouple generates a voltage according to the temperature difference T between the temperature T1 at the junction of the two types of metals (temperature measuring junction) and the temperature T0 at the instrument-side junction (reference junction). An instrument measures this voltage. In practice, during measurement using a thermocouple, a temperature recorder also measures the temperature around the terminal. This is called the reference junction compensation temperature.
For example, if the measuring section is 100°C (212°F) and the terminal is 25°C (77°F), the thermocouple only generates a voltage corresponding to a temperature difference of 75°C (135°F). To display the temperature as 100°C (212°F) in this state, the terminal temperature (reference junction compensation temperature) is added. The relationship between voltage signals from a thermocouple and the temperature is not linear (proportional) but curvilinear. Therefore, direct measurement of voltage values does not allow for conversion to a temperature.
The electromotive force of a thermocouple can be said to be an extremely small value. For example, with a K thermocouple, 1 mV corresponds to a temperature difference of approximately 30°C (54°F). This means that a temperature difference of 1°C (1.8°F) corresponds to approximately 30 μV—an extremely small voltage.

Accuracy

In terms of temperature measurement, the following three elements compose the system accuracy in total.

1. Measurement accuracy
2. Reference junction compensation accuracy
3. The accuracy a thermocouple has on its own
Applicable model
• NR-TH08

### Three-phase AC

Category
The name of a state of an electrical signal
Description
Refers to a 3-system AC in which the waveform of each system is shifted by one third of a cycle (120° or 2π/3 [rad]), respectively. Such shifts in waveforms are called “phase shifts.” Because frequently repeated voltage peaks lead to smaller variations in the rotation speed and force when a motor or similar device is rotated, large machines and equipment are driven by three-phase AC. Also, electricity is generally fed by three-phase AC (electric pole lines are also bundled into a set of three lines), and households use two of these phases. Three-phase is generally transmitted through three lines— called R, S, and T, respectively—and one phase flows between R and S, S and T, and T and R, respectively.

### Transducer

Category
Electrical component
Description
Also called a converter. The word “transducer” is very widely used—for example, to mean a component that converts mechanical signals to electrical signals or optical signals to electrical signals. Specific types of transducers include pressure transducers, power transducers, and ultrasonic transducers.

## V

### Voltage

Category
Unit
Description
The force that attempts to pass electricity is called the “force to generate electricity” or the “electromotive force,” and batteries and power supplies are objects that have this “electromotive force.” “Voltage” refers to this “electromotive force”—a force that pushes out electricity. The voltage is expressed with the symbol “E” and the unit “V (volt).” The voltage is the most basic measurement target and also the only measurement target that an instrument can directly measure. All measurement targets are first converted to voltage signals by a converter (either a built-in or external device) and are then converted to digital numeric data by an A/D converter.
Outputs for recorders that utilize the magnitude of the voltage are analog voltage outputssuch as ±10 V and 1 to 5 V.
Applicable model
• NR Series

## Z

### Z phase

Category
The name of a state of an electrical signal
Description
A type of pulse output from an encoder. => See “Encoder.”

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