Load Cell Glossary Terms

ABSOLUTE PRESSURE 
The pressure measured relative to zero pressure (ie, vacuum).

ACCELERATION 
Acceleration error expressed as percent of SENSITIVITY full scale output per unit acceleration.

AMBIENT TEMPERATURE
The temperature of the medium surrounding the transducer.

AXIAL LOAD 
A load applied along the primary axis of the transducer

BI-DIRECTIONAL 
A transducer which can be used to monitor both positive and negative changes in the measurand.

BRIDGE 
A Wheatstone bridge configuration, which utilises at least one active strain gauge.

CALIBRATION 
The comparison of transducer outputs against the outputs of a reference standard.

COMBINED ERROR (repeatability, non-linearity, hysteresis) 
Maximum deviation from the best straight line drawn through the zero balance point (best fit through zero). Derived from consecutive applications of both decreasing and increasing load (expressed as a % of the full scale output).

COMMON MODE PRESSURE 
See LINE PRESSURE

COMPENSATED TEMPERATURE RANGE 
The range of temperature over which a transducer can operate up to full scale and still meet all specifications.

COMPRESSION LOAD CELL 
A load cell designed for the measurement of compression forces only.

CREEP 
The change in load cell output occurring with time after removal of a load which had been applied for a specific period.

CREEP RECOVERY 
The change in no-load output occurring with time after removal of a load which had been applied for a specific period.

CROSS AXIS SENSITIVITY 
See TRANSVERSE SENSITIVITY.

DEFLECTION
The physical movement of the transducers sensing element between zero and full scale.

DRIFT 
A random change in output under constant load or pressure conditions.

DYNAMIC LOADS 
Are time dependant and act for a small interval of time or change quickly in magnitude or direction e.g. earthquake forces, machinery vibrations, moving vehicles.

ECCENTRIC LOAD
Any load applied parallel to but not concentric with the primary axis.

ENVIRONMENTAL PROTECTION 
The conditions under which the transducer may be expected to perform to its specification often given an IP rating.

EXCITATION, ELECTRICAL 
The recommended voltage or current applied to the input terminals of the transducer.

EXCITATION. ELECTRICAL MAXIMUM 
The voltage or current up to which the transducer can be operated in practical application, and within which the technical data and error specifications are maintained.

FATIGUE RATED 
A term used in conjunction with load cells intended for fatigue applications, usually denotes a derating factor to enhance the operational life.

FREQUENCY, NATURAL 
The frequency or free (not forced) oscillations of the sensing element of a fully assembled transducer.

FULL SCALE 
See RATED CAPACITY

FULL SCALE OUTPUT 
The algebraic difference between the minimum output (normally zero) and the rated capacity.

GAUGE PRESSURE 
Pressure relative to atmospheric. Represents positive difference between measured pressure and existing atmospheric pressure.

HYSTERESIS 
The maximum difference between transducer output readings for the same applied load; one reading obtained by increasing the measurand from zero and the other by decreasing the measurand from rated capacity.

NOTE:-
(a) For load cells primarily intended for weighing applications and pressure transducers normally measured at half full scale output and expressed in percent of full scale.
(b) For load cells primarily intended for force measurements normally measured at zero load after excursion to full scale.

INPUT IMPEDANCE 
The resistance measured across the excitation terminals of a transducer at standard temperature, with no load applied, and with the output terminals open-circuited.

INSULATION RESISTANCE 
The electrical resistance expressed in ohms measured between any electrical connector pin or lead wire and the transducer body or case. Normally greater than 500Mohms measured at 500VDC.

IP RATINGS 
The IP rating system provides a means of classifying the degrees of protection from dust, water and impact afforded by electrical equipment and enclosures. The system is recognised in most European countries.

JUNCTION BOX 
An electrical circuit generally used with load cells enabling the connection of two or more transducers in parallel. Can be supplied with balancing components, to adjust the sensitivities of one or more transducers individually.

LINE PRESSURE 
The maximum pressure in the vessel or pipe for differential pressure measurement.

LOAD BEAM LOAD CELL 
A load cell employing as its primary transduction element a cantilevered beam, in which the strain due to bending is sensed.

LOAD BUTTON 
The spherical like shape of the top surface of a load cell where the load is applied. Often supplied as a screwed in accessory.

MEASURAND 
A physical measured, quantity/property or condition which is measured.

FREQUENCY 
The frequency of free oscillations under no load or no pressure conditions.

NON LINEARITY 
The maximum deviation of the calibration curve above and below the best straight line through the data pointed with the best straight line derived by the method of least squares.

OPERATING TEMPERATURE RANGE 
The range of temperature over which a transducer can operate up to full scale and still meet all specifications.

OUTPUT IMPEDANCE 
The resistance as measured on the output terminals of a transducer at standard temperature, with no measurand applied, and with the excitation terminals open-circuit.

OVERLOAD STOP 
A mechanical device designed to prevent over-stressing of the transducers sensing element.

OVERRANGE, SAFE 
The maximum pressure or load which may be applied to the transducer without causing a permanent change in the performance specifications.

PEAK HOLD 
An electronic device for capturing the peak value of the transitory input of a transducer system.

PRIMARY AXIS 
The axis along which a force or load is designed to act.

RATED CAPACITY 
The maximum measurand that a transducer is designed to measure within its specification.

RATIONALISED OUTPUT 
The maximum difference in output of any number of transducers of the same type and the same range when each is subjected to full scale capacity (expressed as a % of the output at full rated load).

REPEATABILITY 
The ability of a transducer to reproduce output readings when the same measurand value is applied to it consecutively, under the same conditions, and in the same direction. Repeatability is expressed as the maximum difference between output readings as a percent or full scale.

SECONDARY CONTAINMENT 
The maximum pressure a transducers casing can withstand without leakage in the event of a sensing diaphragm mechanical failure.

SENSITIVITY 
The ratio of change in transducer output to change in the value of the measurand.

SHEAR BEAM LOAD CELL 
A load cell employing as its primary transduction element a beam in which the shear strain is sensed.

SIDE LOAD 
Any load acting 90 degrees to the primary axis at the point of axial load application.

SINGLE POINT LOAD CELL 
A load cell whose output is independent of bending moment within qualified limits.

SPAN 
The algebraic difference between the limits of the range from zero to full scale.

STANDARD TEST CONDITIONS (OR REFERENCE CONDITIONS) 
The environmental conditions under which measurements should be made when measurements under any other condition may result in disagreement between various observers at different times and places. These conditions are as follows:-

Temperature: 23°C ±2°C
Barometric pressure: 950 to 1085 mbar

STRAIN GAUGE 
An electrical resistor whose resistance varies with applied mechanical strain.

THERMAL SENSITIVITY REPEATABILITY 
The maximum difference between electrical outputs at full range input obtained after cycling the transducer a specified number of times over the rated temperature range. It is expressed as a percentage of full range output per degree C.

THERMAL SENSITIVITY SHIFT 
The change in rated output due to a change in ambient temperature. Usually expressed as a percentage change or reading per degree C change in ambient temperature, over the compensated temperature range.

TARE 
Amount deducted from gross weight in ascertaining net weight.

TARE OFFSET 
An electrical offset applied to a transducer's output to cancel the effect of a tare load.

THERMAL ZERO REPEATABILITY 
The maximum difference between electrical outputs at zero applied input obtained after cycling the transducer a specified number of times over the rated temperature range. It is expressed as a percentage of full range output per deg C.

THERMAL ZERO SHIFT 
The change in zero balance due to a change in ambient temperature. Usually expressed as a percentage change in full scale output per degree C change in ambient temperature over the compensated temperature range.

TORQUE TRANSDUCER 
A transducer whose output is proportional to applied torsional moment about the primary axis.

TRANSDUCER 
A device which when acted upon by a physical stimulus produces an electrical output in proportion to that stimulus.

TRANSDUCTION ELEMENT 
The electrical portion of a transducer in which the output originates.

TRANSMITTER 
A transducer with integral active electronics which can include voltage or current amplifiers and/or integral voltage/current regulation.

TRANSVERSE SENSITIVITY 
The sensitivity of a transducer to transverse acceleration or other transverse measurand.

WET/DRY 
Describes the operational condition: which must be complied with for the primary and reference sides of a pressure transducer, ie. the reference side must always be maintained in clean, dry, non-corrosive conditions.

WET/WET 
As per WET/DRY except that the restrictions the reference side of the transducer are waived.

ZERO BALANCE 
The output signal of a transducer at rated excitation and with no measurand applied. usually expressed in percent of full scale.