Innovative Measurement Solutions
This purpose of this document is to provide a comprehensive, alphabetical list of terms and definitions commonly employed in the terminology and performance parameters relative to specifications for strain gauge-based transducers and related devices. The definitions herein are compatible with common understanding in the industrial community.
ACCURACY
Stated as a limit tolerance that defines the average deviation between Actual Output and Theoretical Output. In practical transducer applications, the potential errors of nonlinearity, hysteresis, nonrepeatability, and temperature effects do not normally occur simultaneously, nor are they necessarily additive. Therefore, accuracy is calculated based upon the RMS value of potential errors, assuming a defined temperature range, full rated load applied, and proper setup and calibration. Potential errors in other components of the measuring system (e.g., readout devices, structures, terminal connections, mechanical interfaces) are not included.
AMBIENT CONDITIONS
The conditions (humidity, pressure, temperature, etc.) of the environment surrounding the transducer.
AMBIENT TEMPERATURE
The temperature of the environment surrounding the transducer.
ANGULAR LOAD, CONCENTRIC
A load applied concentric with the Primary Axis at the point of application, and at some angle with respect to the Primary Axis.
ANGULAR LOAD, ECCENTRIC
A load applied eccentric with the Primary Axis at the point of application, and at some angle with respect to the Primary Axis.
APPLIED LOAD
A mechanical force introduced to a transducer for purposes of producing a measurable electrical value.
AXIAL LOAD
A load applied along a line concentric with the Primary Axis.
BRIDGE RESISTANCE (WHEATSTONE)
The bridge input resistance is measured across the excitation terminal points in strain gauge-based transducers. The bridge output resistance is measured across the signal terminal points.
CALIBRATION
The comparison of a transducer output signal against a known standard.
CALIBRATION CURVE
A comparison of the transducer output to a known standard when the output is measured between the terminal points of zero (no-load) and rated capacity.
CAPACITY
See Rated Capacity.
COMBINED ERROR (Nonlinearity and Hysteresis)
The maximum deviation from the straight line drawn between the terminal points of zero (no-load) and rated capacity, usually expressed as a percentage of the rated output and measured on both increasing and decreasing loads.
COMPENSATION
The utilization of supplementary devices, materials, or processes to minimize known sources of error.
CREEP
The change in transducer (load cell) output occurring with time, while under load, with all environmental conditions and other variables remaining constant.
CREEP RECOVERY
The change in the transducer output signal occurring with time immediately after removal of a load which had been applied for a specified time interval.
CREEP RETURN
The difference between the transducer output signal prior to application of a load and the output signal following removal of the load for the same time period.
CROSSTALK
With one transducer component loaded to capacity and the other unloaded, the output of the unloaded component should not exceed a specified tolerance.
CYCLIC LOADING
Cyclic loads on a structure can lead to fatigue damage, cumulative damage, or failure.
DEAD LOAD
Permanent or static loads, such as a frame or structure.
DEFLECTION
The change in position of the transducer along the primary axis between no-load and rated load conditions.
DRIFT
A random change in output under constant conditions.
DYNAMIC LOAD
A non-static load that may involve impact, momentum, vibration, etc.
ECCENTRIC LOAD
Any load applied parallel to, but not concentric with, the primary axis.
ERROR
The algebraic difference between the indicated value and true value being measured.
EXCITATION
The voltage or current applied to the input terminals of the transducer bridge.
FATIGUE CAPACITY
Capacity based on a specified number of load cycles from zero to full fatigue capacity.
FULL SCALE OUTPUT (FSO)
The output corresponding to the signal generated when loaded to rated capacity.
HYSTERESIS
The algebraic difference between output at a given descending load point and output at the same load point ascending.
IMPACT LOAD
A load whose time of application is less than one-third of the natural period of vibration of that material.
INPUT RESISTANCE
Resistance measured at excitation terminals with no load applied.
INSULATION (LEAKAGE) RESISTANCE
DC resistance measured between the transducer bridge circuit and various reference points.
LIVE LOAD
An imposed load borne for weight, force, torque, or pressure measurement.
LOAD
A weight, force, torque, or pressure applied to the transducer.
LOAD CELL
A precision, electromechanical spring element producing a voltage output proportional to load.
LOAD MODE
The method of load application, e.g., compression, tension, torsional, multi-axis.
MAXIMUM LOAD / SAFE / ULTIMATE / MOMENT / TORQUE / SIDE LOAD
Various maximum limits defined by manufacturer beyond which performance or structure may be compromised.
MEASURING RANGE
Range between minimum and maximum capacity of a transducer for an application.
MODE
Direction/type of applied load.
NATURAL FREQUENCY
Frequency of free oscillations with no load.
NO LOAD
Condition with no load applied.
NOMINAL LOAD LIMIT CAPACITY
Designed normal operating maximum capacity.
NONLINEARITY
Difference between output at a load point and theoretical straight line.
NONREPEATABILITY
Maximum difference between repeated load readings.
OUTPUT
Electronic signal produced by the transducer.
OVERLOAD RATING (Safe/Ultimate)
Maximum load that can be applied without permanent shift or failure.
OUTPUT RESISTANCE
Resistance measured at signal terminals with no load applied.
PRESSURE TRANSDUCER
Device producing a signal proportional to applied pressure.
PRIMARY AXIS
Axis along which the transducer is designed to be loaded.
PSI / PSIA
Pounds per square inch / absolute.
RATED CAPACITY (RC)
Maximum axial load measurable within specs.
RATED OUTPUT (RO)
Difference between output at no-load and with rated load.
REFERENCE STANDARD
Force-measuring device with precisely known characteristics.
RESISTANCE, ELECTRICAL
Degree to which an object opposes electrical current.
RESOLUTION
Smallest change in input producing measurable change in output.
SENSITIVITY
Ratio of change in output to change in mechanical input.
SHUNT CALIBRATION
Electrical simulation of a transducer output signal by resistance connection.
SIDE LOAD / SIDE LOAD REJECTION
Loads perpendicular to the primary axis, and the ability to ignore them.
SIGNAL
Output measured as difference between applied load and minimum load.
SPAN
Value between output at no-load and rated load.
SPECIFICATION
Error limits or requirements to be met.
STABILIZATION PERIOD
Time required for a measured parameter to be considered stable.
STANDARD TEST CONDITIONS
Temperature: 72°F (23°C), Relative Humidity ≤90%, Barometric Pressure: 28-32 inHg, plus gravity and density corrections.
STATIC ERROR BAND
Error band including effects of nonlinearity, hysteresis, and zero return.
STRAIN GAUGE
Device measuring strain by resistance change.
SYMMETRY ERROR
Difference between rated output in tension and compression.
TEMPERATURE EFFECT ON OUTPUT / ZERO BALANCE
Change in output or zero balance with temperature change.
TEMPERATURE RANGE (Compensated / Safe)
Ranges within which performance is maintained or device operates without permanent change.
TERMINAL RESISTANCE (Excitation/Signal)
Resistance measured at specific terminals under standard conditions.
TOGGLE EFFECT
Shift in zero balance from equal tension and compression cycles.
TORQUE TRANSDUCER
Device producing a signal proportional to applied torque.
TRACEABILITY
Link from calibration to primary measurement standards.
ULTIMATE OVERLOAD
Point of structural failure risk.
WHEATSTONE BRIDGE / CIRCUIT
Electrical arrangement to measure unknown resistance.
ZERO BALANCE / ZERO RETURN / ZERO SHIFT / ZERO STABILITY
Definitions relating to output with no load and its stability over time.