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Glossary of Terms

We´ve put together a list of terms that are often seen in the force and pressure measurement industry as a reference for our customers and anyone else who might find it useful. Terms that are seen in blue text can be clicked to open the Wikipedia article if a deeper definition is required. As always, our knowledgeable technical staff at Cooper Instruments is available at (800) 344-3921 orsales@cooperinstruments.com  to help you with any clarification you might need.

 

Accuracy:

  • the degree of closeness of measurements of a quantity to that quantity’s actual (true) value
  • a limit tolerance which defines the average deviation between the actual output versus theoretical output
  • precision in the measurement of quantities and in the statement of physical characteristics

Accuracy is expressed in terms of error as a percentage of the specified value (e.g., 10 volts ± 1%), as a percentage of a range (e.g., 2% of full scale), or as parts (e.g., 100 parts per million).

 

Ambient Conditions: The conditions (humidity, pressure, temperature, etc.) of the medium surrounding the measuring device.

 

Analog: Anything that corresponds, point for point or value for value, to an otherwise unrelated quantity; data represented by continuous values rather than in discrete steps.

 

ANSI: American National Standards Institute: a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States.

 

ASCII (American Standard Code for Information Interchange) : Pronounced “askee”. a seven-bit plus parity character-encoding scheme based on the ordering of the English alphabet. ASCII was established by the American National Standards Institute (ANSI) to achieve compatibility between data services.

 

Axial Load: A load applied along a line concentric with the primary axis.

 

Baud: symbols per second or pulses per second. A unit of communications processing speed in digital data communications systems.

 

Calibration: comparison between measurements – one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device. The comparison of load cell outputs against standard test loads.

 

Capacity: The amount of weight the scale is capable of weighing accurately.

 

Combined Error (Non-linearity and Hysteresis): The maximum deviation from the straight line drawn between the original no-load and rated load outputs 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.

 

Compensated Temperature: The range of temperature over which the transducer is compensated to maintain Rated Output and Zero Balance within specified limits.

 

Creep: The change in transducer output occurring with time, while under load, and with all environmental conditions and other variables remaining constant. Usually measured with Rated Load applied and expressed as a percent of Rated Output over a specific period of time.

 

Deflection: the degree to which a structural element is displaced under a load. It may refer to an angle or a distance.

 

Drift: A random change in Output under constant Load conditions.Also, a continuously upward or downward change in the number displayed on the digital readout. Drift could be due to temperature, static electricity or RFI (radio frequency interference).

 

Environmentally Protected: Device is protected from normal environmental factors in indoor or outdoor applications.

 

Error: the difference between a computed, estimated, or measured value and the accepted true, specified, or theoretically correct value. In load measuring terms, the algebraic difference between the indicated and true value of the load being measured.

 

Excitation: The voltage or current applied to the input terminals of the transducer.

 

Hermetically Sealed: airtight: impervious to moisture, air and gas.

 

Hysteresis: The maximum difference between the transducer output readings for the same applied load; one reading obtained by increasing the load from zero and the other by decreasing the load from Rated Output. Usually measured at half Rated Output and expressed in percent of Rated Output. Measurements should be taken as rapidly as possible to minimize Creep.

 

IP Ratings (Ingress Protection Rating): Consists of the letters IP followed by two digits and an optional letter. As defined in international standard IEC 60529, it classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures.

 

Linearity: Refers to the quality of delivering identical sensitivity throughout the weighing capacity of a scale or balance.

 

Load Cell: A device which produces an Output signal proportional to the applied weight or force. Types of load cells include beam, S-beam, platform, compression and tension.

 

Natural Frequency: The frequency of free oscillation under no-load conditions.

 

NEMA: National Electrical Manufacturers Association

 

NIST (National Institute for Standards and Technology): An agency of the federal government to which all precision measurements are traceable. Formerly the National Bureau of Standards (NBS)

 

Non-linearity: The maximum Deviation of the Calibration Curve from a straight line drawn between the no-load and Rated Load outputs, expressed as a percentage of the Rated Output and measured on increasing load only.

 

Non-repeatability: The maximum difference between transducer output readings for repeated loadings under identical loading and environment conditions.

 

NTEP (National Type Evaluation Program): A program of cooperation between the National Conference On Weights & Measures, NIST, state weights and measures officials and the private sector for determining conformance of weighing equipment with the provisions of H-44.

 

OEM (Original Equipment Manufacturer): A manufacturer who produces equipment for use or inclusion by another manufacturer in its product.

 

Operating Temperature: The extremes of temperature within which the transducer will operate without permanent adverse change to any of its performance characteristics.

 

Output: The signal (voltage, current, pressure, etc.) produced by a load cell. Where the output is directly proportional to excitation, the signal must be expressed in terms such as Volts per Volt, Millivolts per Volt, or Volts per Ampere, etc., of excitation.

 

Primary Axis: The axis along which the transducer is designed to be loaded; normally its geometric centerline.

 

Rated Load (Rated Capacity): The maximum Axial Load that the transducer is designed to measure within its specifications.

 

Rated Output: The signal (voltage) produced by the transducer; the algebraic difference between the Outputs at no-load and at Rated Load.. Where the output is directly proportional to excitation, the signal is expressed in terms of millivolts / volt (mV/V) of excitation.

 

Reference Standard: A force-measuring device whose characteristics are precisely known relative to a primary standard.

 

Repeatability: The maximum difference between load cell output readings for repeated loadings under identical loading and environmental conditions; the ability of an instrument, system, or method to give identical performance or results in successive instances. Also called reproducibility or repeatability.

 

Resistance: Opposition to current flow offered by a purely resistive component; simple opposition to current flow. Measured in ohms.

 

Resolution: The smallest change in mechanical input which produces a detectable change in the output signal.

 

Safe Overload: The maximum, temporary or accidental load in percent of Rated Capacity which can be applied without producing a permanent shift in performance characteristics beyond those specified.

 

Sensitivity: The ratio of the change in output to the change in mechanical input.

 

Shunt Calibration: Electrical simulation of transducer output by insertion of known shunt resistors between appropriate points within the circuitry.

 

Span: The difference between the highest value and the lowest value.

 

Strain Gauge: A device for detecting the strain that a certain force produces on a body. The gauge consists of one or more fine wires cemented to the surface under test. As the surface becomes strained, the wires stretch or compress, changing their resistance. Several strain gauges are used to make up a load cell.

 

Tare: The weight of an empty container or vehicle, or the allowance or deduction from gross weight made on account thereof.

 

Terminal Resistance, Input (Excitation): The resistance of the load cell circuit measured at the excitation terminals at standard temperature with no load applied and with the output (signal) terminals open-circuited.

 

Terminal Resistance, Output (Signal): The resistance of the load cell circuit measured at the output signal terminals at standard temperature with no load applied and with the excitation terminals open-circuited.

 

Tolerance: The amount of error that is allowed in a value. It is usually expressed as a percent of nominal value, plus or minus so many units of measurement.

 

Transducer: A device that converts energy from one form to another.

 

Zero Balance: The output signal of the transducer with rated Excitation and with no-load applied, usually expressed in percent of Rated Output.