# Load Cell and

Transducer Glossary

Common frequently used terms related to load cells and force measurement

## Accuracy |
Describes the closeness of agreement between a measured value and the reference value; it is often interpreted as a combination of the measurement trueness and measurement precision |

## Ambient Temperature |
The temperature of the medium surrounding the load cell; the temperature of the measuring environment. |

## Calibration |
Process that compares a measurement device—often referred to as the measurand or device under test (DUT)—to a reference standard; if the measurement device exhibits excessive measurement error, the measurement device is often adjusted to reduce this error |

## Calibration Curve |
A equation that characterizes the relationship between a sequence of applied loads and the resulting outputs from the measurement device; this relationship is typically expressed as a linear equation, series of linear equations, or polynomial equation |

## Capacity |
The maximum axial load a load cell is designed to measure within its specifications. |

## Compensated Temperature Range |
The range of temperatures over which the temperature drift specifications are valid; temperature drift is typically expressed by the Temperature Effect on Zero and Temperature Effect on Output terms. |

## Creep |
When a load cell is subjected to a constant / static load, Creep is the resulting change in load cell output that occurs over time; this value is usually measured at the load cell capacity when that load is applied for 30 minutes; the result is expressed as a percent of rated output over the loading period. |

## Creep Recovery |
The change in load cell signal occurring with time immediately after removal of a load which has been applied for a specified time interval, environmental conditions, and other variables remaining constant during the loaded and unloaded intervals. Normally expressed in units of % of applied load over a specified time interval. Normally the applied interval and the recovery interval are equal. It is common for characterization to be measured with a constant load or near capacity. |

## Creep Return |
The difference between load cell signal immediately after removal of a load which has been applied for a specified time interval, environmental conditions, and other variables remaining constant during the loaded interval, and the signal before the application of the load. Normally expressed in units of % of applied load over a specified time interval. It is common for characterization to be measured with a constant load at or near capacity. |

## Dead Load |
Loads that are constant over time, such as frames, structures, or other immovable objects. Other terms are permanent load or bearing load. |

## Deflection |
Expresses the change in the height of a load cell (measured along its loading axis) when it is loaded to its capacity |

## Drift |
Random change in the output of a load cell over time; can affect the zero point or output sensitivity of the load cell |

## Dynamic Load |
Loads that change rapidly, often bidirectionally (ascending and descending); examples include moving vehicles, machine vibration, wind gusts |

## Eccentric Load |
Any load applied parallel to but not concentric with the primary axis; applies a torque to the load cell measuring element |

## Error (Measurement Error) |
The measured value minus the reference value; typically applies the performance of a measurement device or measurement process |

## Excitation |
Excitation is the voltage or current applied to the input terminals of the load cell. |

## Full-Scale Output |
Also known as Rated Output or Sensitivity; the denominator term used to calculate a result that is expressed as a percent of full scale (%FS) |

## Hysteresis |
Performance specification that characterizes the difference between when a load cell is measuring ascending and descending loads. In a typical calibration, a load cell is subjected to a series of ascending loads and, immediately after reaching full-scale, the load cell will be subjected to a single descending load point (often at 40% of scale); the difference between that measurement point on the way up and on the way down becomes the Hysteresis specification |

## Input Resistance |
Electrical resistance of the input to load cell bridge circuit measured across the positive and negative excitation terminals while the load cell is unloaded |

## Insulation (Leakage) Resistance |
The DC (direct current) resistance measured at 50 volts under standard test conditions between the bridge circuit and transducer, circuit and cable shield, and transducer element and cable shield |

## Load |
The force or weight applied to a load cell |

## Load Cell |
A precision, electromechanical spring element commonly constructed of alloy tool steel, stainless steel, or aluminum alloy; outputs a low-level voltage signal that is proportional to the applied load |

## Maximum Load |
The highest load in a specific test or application, which may be any load up to the load cell capacity; may not significantly exceed load cell capacity, upper limit is usually 110% of capacity |

## Measuring Range |
The difference between maximum load and minimum load in a specific test or application |

## Minimum Dead Load or MDL |
The smallest load for which specified performance will be met. It is normally equal to or near NO LOAD in single modea applications and is of necessity equal to no load in double mode applications. |

## Minimum Load |
The lowest load in a specific test or application, differing from no load by the weight of fixtures and load receptors which are attached plus any intentional pre-load which is applied. |

## Mode |
Also commonly referred to as Loading Mode; the direction of the load; tension and compression are loading modes |

## mV/V |
The ratio between the load cell signal (output) and the excitation voltage (input) |

## Natural Frequency |
Often termed the Ringing Frequency of the load cell; this is the frequency at which the load cell oscillates under conditions when unloaded; often used to as an implicit measure of load cell responsiveness in the time domain |

## No Load |
When the load cell is in its normal physical orientation, without any fixtures installed, and no external force is being applied |

## Non-linearity |
Characterizes the deviation a calibration curve has from a straight line; the straight line is drawn between the no-load and rated load points. |

## Non-repeatability (Repeatability) |
The maximum difference between load cell output readings for repeated rated loadings or unloadings under identical environmental conditions. |

## NTEP |
NTEP stands for National Type Evaluation Program, a certification organization created by the U.S. Department of Commerce’s National Institute of Standard and Technology (NIST) and the National Conference on Weights and Measure (NCWM). |

## Operating Temperature Range |
As referred to as the Safe Temperature Range; the temperature extremes within which a load cell will operate without permanent adverse change to its performance characteristics. |

## Output Resistance |
The resistance expressed in ohms of the strain gauge bridge circuit, measured at the positive and negative signal terminals with no load applied and input terminals open-circuited. |

## PLC (Programmable Logic Controller) |
An industrial computer designed to monitor and instruct manufacturing processes. |

## Primary Axis |
The axis along which the load cell is designed to be loaded; normally its geometric centerline. |

## Rated Capacity |
The maximum axial load that the load cell transducer is designed to measure within its technical specifications. |

## Rated Output (Sensitivity, Full-Scale Output) |
The algebraic difference of the load cell output at no-load compared to its output with the rated load applied, usually expressed in a ratio millivolts/volt (mV/V) of excitation. Also known as RO. |

## Recommended Excitation |
The excitation voltage, usually expressed in VDC, for optimal performance of the transducer to operate within its specifications. |

## Reproducibility |
The degree of agreement between the results of measurements taken under changing conditions or locations. |

## Resistance (Electrical) |
A measure of the opposition of the flow of electrical current in a wired circuit. Resistance, also called ohmic resistance, is measured in Ohms (Ω). |

## Resolution |
The smallest change in load which produces a detectable change in the signal. |

## Safe Overload |
Maximum (axial) load that can be (statically) applied without creating a permanent shift in performance, expressed as a percent of full-scale |

## Sensitivity |
See Rated Output |

## Signal |
The absolute level of the measurable quantity into which a force input is converted. |

## Span |
Another name for rated output. |

## Specification |
The error limits within which a load cell should function for a given technical parameter. |

## Strain Gauge |
A strain gauge sensor uses electrical resistance to measure deformation or displacement from applied stress or strain. |

## Temperature Range, Compensated |
The range of temperature over which the load cell is compensated to maintain output and zero balance within specified limits; range of temperatures over which the Temperature Effect on Zero and Temperature Effect on Span specifications apply |

## Temperature Range, Operating |
The extremes of ambient temperature within which the load cell will operate without permanent adverse change to any of its performance characteristics. |

## Temperature Shift (Effect) on Output |
The effect of temperature on a load cell’s sensitivity, usually expressed as a percentage of load per degree Fahrenheit (Celsius) change in temperature. |

## Temperature Shift (Effect) on Zero |
The change or shift in zero balance due to a change in ambient temperature and causing the output curve to move up or down across the output axis. |

## Ultimate Overload |
The maximum load that can be applied without causing structural/catastrophic failure, usually expressed as a percentage of full-scale capacity. |

## Wheatstone Bridge |
A simple electrical circuit of four resistors connected as a quadrilateral used for measuring an unknown resistance. |

## Zero Balance (Zero Offset) |
The output signal of the load cell with rated excitation and with no-load applied; the amount of deviation in output between true zero and a real load cell with zero load and usually expressed in percent of rated output. |

## Zero Dead Band |
Another name for zero float. |

## Zero Float |
The shift in zero balance resulting from a complete cycle of equal tension and compression loads. Normally expressed in units of %FS and usually characterized at FS = Capacity. |

## Zero Return |
The difference in zero balance measured immediately before applying a rated load for a specified duration compared to the measurement after removal of the load and when the output has stabilized. |

## Zero Shift |
A permanent change in the no-load output. |

## Zero Stability |
The degree to which the transducer maintains its zero balance with all environmental conditions and other variables remaining constant. |