3   Devices for measurement

3.1 (4.1)
measuring instrument

device used for making measurements, alone or in conjunction with one or more supplementary devices

NOTE 1   A measuring instrument that can be used alone is a measuring system.

NOTE 2   A measuring instrument may be an indicating measuring instrument or a material measure.

3.2 (4.5)
measuring system

set of one or more measuring instruments and often other devices, including any reagent and supply, assembled and adapted to give information used to generate measured quantity values within specified intervals for quantities of specified kinds

NOTE   A measuring system may consist of only one measuring instrument.

3.3 (4.6)
indicating measuring instrument

measuring instrument providing an output signal carrying information about the value of the quantity being measured

EXAMPLES   Voltmeter, micrometer, thermometer, electronic balance.

NOTE 1   An indicating measuring instrument may provide a record of its indication.

NOTE 2   An output signal may be presented in visual or acoustic form. It may also be transmitted to one or more other devices.

3.4 (4.6)
displaying measuring instrument

indicating measuring instrument where the output signal is presented in visual form

3.5 (4.17)
scale of a displaying measuring instrument

part of a displaying measuring instrument, consisting of an ordered set of marks together with any associated quantity values

3.6 (4.2)
material measure

measuring instrument reproducing or supplying, in a permanent manner during its use, quantities of one or more given kinds, each with an assigned quantity value

EXAMPLES   Standard weight, volume measure (supplying one or several quantity values, with or without a quantity-value scale), standard electric resistor, line scale (ruler), gauge block, standard signal generator, certified reference material.

NOTE 1   The indication of a material measure is its assigned quantity value.

NOTE 2   A material measure can be a measurement standard.

3.7 (4.3)
measuring transducer

device, used in measurement, that provides an output quantity having a specified relation to the input quantity

EXAMPLES   Thermocouple, electric current transformer, strain gauge, pH electrode, Bourdon tube, bimetallic strip.

3.8 (4.14)
sensor

element of a measuring system that is directly affected by a phenomenon, body, or substance carrying a quantity to be measured

EXAMPLES   Sensing coil of a platinum resistance thermometer, rotor of a turbine flow meter, Bourdon tube of a pressure gauge, float of a level-measuring instrument, photocell of a spectrometer, thermotropic liquid crystal which changes colour as a function of temperature.

NOTE   In some fields, the term “detector” is used for this concept.

3.9 (4.15)
detector

device or substance that indicates the presence of a phenomenon, body, or substance when a threshold value of an associated quantity is exceeded

EXAMPLES   Halogen leak detector, litmus paper.

NOTE 1   In some fields, the term “detector” is used for the concept of sensor.

NOTE 2   In chemistry, the term “indicator” is frequently used for this concept.

3.10 (4.4)
measuring chain

series of elements of a measuring system constituting a single path of the signal from a sensor to an output element

EXAMPLE 1   Electro-acoustic measuring chain comprising a microphone, attenuator, filter, amplifier, and voltmeter.

EXAMPLE 2   Mechanical measuring chain comprising a Bourdon tube, system of levers, two gears, and a mechanical dial.

3.11 (4.30)
adjustment of a measuring system
adjustment

set of operations carried out on a measuring system so that it provides prescribed indications corresponding to given values of a quantity to be measured

NOTE 1   Types of adjustment of a measuring system include zero adjustment of a measuring system, offset adjustment, and span adjustment (sometimes called gain adjustment).

NOTE 2   Adjustment of a measuring system should not be confused with calibration, which is a prerequisite for adjustment.

NOTE 3   After an adjustment of a measuring system, the measuring system must usually be recalibrated.

3.12
zero adjustment of a measuring system

zero adjustment

adjustment of a measuring system so that it provides a null indication corresponding to a zero value of a quantity to be measured