Glossary of Basic Material Testing and Force Measurement Terms
Bending Test - A sample is supported at both ends and a compressive force is applied to the middle of the sample.
Break Force - Force at which a break is defined
Break Load - Load at which a break is defined
Break Strength - Force at which a break is defined divided by sample width
Cohesive Strength - Measure of force / area of two substances that stick to each other
Cohesiveness - Stickiness
Compression - Application of a force to reduce a samples height
Creep - Strain caused by stress that occurs over time
Deformation - A change in dimensions of a material
Elasticity - Tendency of a material to return to its original shape after it has been stretched or compressed
Elongation - Extension of a specimen which has been stretched in a test. The percentage elongation is an indication of ductility
Extension - Measurement of movement of the testing machine
Extensometer - Device to measure accurately the movement of a sample either by contacting directly on the sample or a non-contacting optical method
Fatigue - Fatigue is a process by which a material is weakened by cyclic loading
Fracture - A break in the sample
Hardness - Resistance to permanent deformation
Modulus - The physical measurement of stiffness in a material, equaling the ratio of applied load to the resultant deformation of the material
Preload - Load applied to a sample before it is tested to remove unwanted sample or fixture movement
Resilience - The ability of a material to return to its original shape after the removal of a stress that has produced elastic strain
Rupture - When a sample bursts or is torn
Stiffness- Stiffness is the resistance of an elastic body to deflection by an applied force
Strain- The amount of deformation a material experiences per unit of original length in response to stress
Strength- The stress an object can endure before it breaks
Stress- Force that a material is subjected to per unit of original area
Viscosity - The thickness or resistance to flow of a liquid
Yield - The stress at which a material exhibits a specified deviation from proportionality of stress and strain
Young's Modulus - The Young's Modulus result is calculated as being the gradient of the modulus line on a stress vs. strain graph
Glossary of Basic Weighing Terms
A/D (Analog to Digital)- Conversion of continuously varying (analog) voltage levels to discrete binary-numbered (digital) values (e.g., a load cell output can be fed through an A/D convertor to produce a continuous stream of digitized information and sent to a digital indicator).
Accuracy- 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 load cell.
Calibration - The comparison of load cell outputs against standard test loads.
Capacity- The amount of weight the scale is capable of weighing accurately.
Checkweigher- A scale used to verify predetermined weight within prescribed limits.
Compensation- The utilization of supplementary devices, materials or processes to minimize known sources of error.
Cornerload- The ability of an instrument to deliver the same weight reading for a given object on the corners of the weighing pan.
Deflection- The change in length along the Primary Axis of the load cell between no-load and Rated Load conditions.
Divisions- Determines the amount of increments a scale offers.
Drift- A continuously upward or downward change in the number displayed on the digital readout. This could be due to temperature, static electricity or RFI (radio frequency interference).
Environmentally Protected- Refers to load cells which have a strain gauge cavity filled with a potting compound. The cavity opening is also generally protected with loose-fitting side plates or molded plastic to protect against physical damage. These cells are protected from normal environmental factors in indoor or outdoor applications. They should not be submersed or washed down.
Explosion Proof Enclosure- An enclosure that is capable of withstanding an explosion of a specified gas or vapor which may occur within it and of preventing the ignition of the gas surrounding the enclosure. The enclosure also must operate at such an external temperature so that it is incapable of igniting its surrounding atmosphere.
Factory Mutual (FM) System Approved- All products displaying this symbol have been approved for use in hazardous (classified) locations when following the proper installation procedures and drawings, and utilizing intrinsic safety barriers.
Hermetically Sealed- Refers to load cells which have a metallic protective cover welded or soldered in place to protect the strain gauge cavity. Some cells of this type have additional protection at the cable entry such as a glass-to-metal seal. These load cells provide the best possible protection in harsh chemical or washdown environments.
Hysteresis- The maximum difference between load cell output readings for the same applied load. One reading is obtained by increasing the load from zero and the other reading is obtained by decreasing the load from rated load. Measurements should be taken as rapidly as possible to minimize creep.
Interface- A device or circuit that allows two units to communicate. Some of the standard interfaces used in the scale industry are 20 mA current loop, BCD, RS-232, RS-422 and RS-485.
Intrinsically Safe System- An assembly of interconnected intrinsically safe apparatus, associated apparatus and interconnecting cables in which the parts of the system, which may be used in hazardous (classified) locations, are intrinsically safe circuits; may include more than one intrinsically safe circuit.
IP Ratings (Ingress Protection)- 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.
J-BOX (Junction Box)- A box or enclosure used to join different runs of cable or wiring; it contains space and terminals for connecting and branching the enclosed conductors and adjustments to provide load cell trimming.
Linearity- Refers to the quality of delivering identical sensitivity throughout the weighing capacity of a scale or balance.
Load- The weight or force applied to the load cell.
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.
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.
Overload Rating, Safe- The maximum load, in percent of Rated Capacity, which can be applied without producing a permanent shift in performance characteristics beyond those specified.
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.
Resolution- The smallest change in mechanical input which produces a detectable change in the output signal. The size of the increment when moving from one electronic digit to the next. Resolution = Capacity/Divisions.
Scale- A device for weighing, comparing and determining weight or mass.
Stabilization Period- The time required to ensure that any further change in the parameter being measured is tolerable.
Tare- The weight of an empty container or vehicle, or the allowance or deduction from gross weight made on account thereof.
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.
Weight- The force or amount of gravitational pull by which an object or body is attracted toward the center of the earth.
Key Terms Used in Overhead Force Measurement
Excitation- The voltage inputted to a load cell.
Force- A push or pull that one body exerts on another.
Shackle- The common forged hardware bow and pin connected to a dynamometer.
Signal- The voltage output of a load cell.
Torque- A force applied a distance away from an axis of rotation. Torque = Force x Distance
Tension- A force pulling equally from two directions in the same axis.
Dynamometer- An instrument that displays the tension force exerted between the two attached shackles.
Crane Scale- A crane scale is a dynamometer outfitted with equipment appropriate for suspended weighing, such as large openings in upper shackles, hooks on the bottom and large dials for easy distant viewing.
Indicator- The instrumentation designed to convert the meaningless voltage signal from the sensor into a reading understandable for the user.