Glossary of industrial scales and weighing

A

accumulator

A device that receives, totals and stores weighing data, designed as a circuit or register linked to a computer.

accuracy

The precision of 1) measurements made by a weighing system, and 2) the statement of physical characteristics. It is expressed in terms of error, as a percentage of: a) the specified value (e.g., 10 volts ± 1%), b) a range (e.g., 2% of full scale), or c) as parts (e.g., 100 parts per million).

analog-to-digital (A/D)

analog-to-digital converter (ADC)

The conversion of analog (continuously varying) voltage levels to digital (binary-numbered) values. E.g., an analog-to-digital converter can translate load cell output that is fed into it, into a continuous stream of digitized information to be sent to a digital indicator.

ambient conditions

Humidity, pressure, temperature and other conditions present in the medium surrounding a load cell.

ampere

Unit of electric current intensity, measured as 6.24 x 1018 electrons passing a point in one second. Abbreviated amp.

analog

Information represented by continuous values instead of discrete steps; point for point or value for value data that corresponds to an otherwise unrelated quantity.

angular load, concentric

Load applied concentric with (common center), and at an angle to, the primary axis at the point of application.

angular load, eccentric

Load applied eccentric with (off center), and at an angle to, the primary axis at the point of application.

aperture

Percentage range of full scale capacity, over which digital weight indicator functions AZM (Automatic Zero Maintenance) and PAZ (Push-button Auto Zero) will operate, according to Handbook 44.

approved

System or equipment that is acceptable to the authority with jurisdiction over the area in which it will be used.

American Standard Code for Information Interchange (ASCII)

Seven-bit plus parity code established by the American National Standards Institute (ANSI) to achieve compatibility between data services. Pronounced "askee".

associated apparatus

Devices relied upon to maintain intrinsic safety, designed with circuits that may not be intrinsically safe themselves, but may affect the energy in intrinsically safe circuits.

asynchronous transmission

Data transmission where time intervals between transmitted characters may be of unequal length. Controlled by start bits at the beginning and stop bits at the end of each character.

authority having jurisdiction

May be a federal, state, local or other regional institution, department or individual that has jurisdiction where public safety is primary. E.g., fire chief, fire marshal, chief of fire protection bureau.

auto-ignition temperature (AIT)

(Also ignition temperature); lowest temperature that will cause a substance to initiate or induce self-sustained combustion independently of heating or heated equipment.

automatic zero maintenance (AZM)

Electronic method of providing "true zero" on a digital scale, at all times. Compensates for conditions like indicator or load cell drift or debris on a scale platform by electronically tracking out minor variations around zero.

automatic shut-off

Function that turns off a weighing device or unit after a pre-set duration, if no active weighing occurs during that time.

average piece weight (APW)

Measurement of total weight divided by number of samples weighed in one batch on a counting scale. Used to determine the count of pieces during normal operation, where total weight of large batches is divided by average piece weight.

axial load

Load applied along a line concentric with the primary axis at the point of application.

B

baud

A unit of communications processing speed in digital data communications systems, measured as the number of discrete conditions of signal events per second. If each signal event represents only one bit condition, baud rate equals bits per second (BPS).

beam

A device used as an indicator for a lever scale.

bezel

A holder that is designed to receive and position the edges of a lens, meter, window or display.

bi-direction

Information flow in either direction on a wire between pieces of equipment that are equipped for both receiving and transmitting data. May be abbreviated bi-di or BiDi.

binary-coded decimal (BCD)

A data coding system in which the decimal numbers 0 through 9 are represented by four binary bits. E.g., the binary coded decimal equivalent of the number 187 is 0001 1000 0111.

bit

The smallest unit of information in a binary system, consisting of a 0 or a 1. Abbreviated from "binary digit".

blackout

A sudden loss of AC line power which normally occurs due to an overload or other power failure.

Board of Governors

The body of officials from the National Conference on Weights and Measures that sets National Type Evaluation Program (NTEP) policy and has final say in disputes.

bridge circuit

A network of four "leg" components connected in such a way that the input signal may be applied across two branches in parallel, and the output signal taken between two points, one on each side of the parallel branches. The output voltage is zero when the output points are at the same potential, which occurs at some ratio of the resultant four arms of the circuit, and the bridge is said to be balanced or set to null at that point.

brownout

A power company's deliberate lowering of line voltage in order to reduce load demands.

C

calibration

A comparison of the outputs of load cells against standard test loads, to check for accuracy and any errors in measurement.

calibration curve

A record (graph) of the comparison of load cell outputs against standard test loads.

calibration error

Any difference between what the weighing equipment reads on the display, and the item's true mass as measured by a calibrated instrument.

cantilever beam

A beam-type load cell with strain gauges or load-sensing elements mounted on the inside perimeter of a machined-out center.

capacitance

The ability of a component or material to store an electrostatic charge; measured in farads. Because the farad is a very large quantity, capacitance in electronic applications is usually expressed in millionths of a farad (microfarads) or millionths of a millionth of a farad (pico farads).

capacity

The amount of weight that a scale or weighing device can accurately weigh.

central processing unit (CPU)

A computer module or chip that controls processing operations for the device by fetching, decoding and executing instructions.

challan

A payment or delivery receipt.

check rods

Rods that are installed on a vessel or other weighing system component to prevent gross tipping or extended travel. They do not interfere with normal travel or expansion.

check weigher

A scale used to verify predetermined weight within prescribed limits.

class III scales

Classes of scales used in commercial weighing that are not otherwise specified. These include grain test scales, retail precious metals and semiprecious gem weighing, animal scales, postal scales, and scales used to determine laundry charges.

class IIIL scales

Vehicle, axle-load, livestock, railway track scales, crane and hopper (other than grain hopper) scales.

complementary metal oxide semiconductor (CMOS)

Chip technology characterized by a low power requirement and high noise immunity, but susceptible to damage by electrostatic discharge (ESD).

combined error (non-linearity and hysteresis)

The maximum deviation from the straight line drawn between the original no-load and rated load outputs (measured on both increasing and decreasing loads), and expressed as a percentage of the rated output.

compensation

Use of supplementary equipment, materials or processes in order to minimize any known sources of error.

compression (physical)

A force applied to a strain gauge that decreases gauge resistance by causing the gauge wires to compress and their cross-sectional area to increase. Not to be confused with data compression.

concentrated load capacity (CLC)

Maximum load that can be placed anywhere on the platform of a vehicle, axle-load or livestock scale using the prescribed test pattern (an area at least 4 feet long and as wide as the scale platform), as designated by the manufacturer.

conformally coated

Load cells that have a protective coating applied over the strain gauges, terminal strip, etc., within the gauged cavity, which may also be covered with side plates to protect against physical damage. These cells are designed for use in normal indoor applications and should not be used in wet or washdown applications.

continuous mode

Transmission of serial output data in which information is transmitted automatically following each indicator display update. It is usually used to interface indicators to remote devices that require constant data updating, like computers and score boards.

control drawing

A drawing or document which details the allowed interconnections between the intrinsically safe or associated apparatus and is provided by the manufacturer of the equipment.

cornerload

The ability of an instrument to deliver the same weight reading for an object placed on the corners of the weighing pan.

cornerload error

Variations in the weight of an object that is moved to corner positions on the weighing pan.

count

The smallest increment of weight that is displayed by the instrument.

creep

Change in load cell output that occurs with time, while under load, and with all environmental conditions and other variables remaining constant. It is usually measured with rated load applied and expressed as a percent of rated output over a specific duration.

creep recovery

The change in no-load output occurring with time, after removal of a load which has been applied for a specific period of time. It is usually measured over a specified time period that immediately follows the removal of rated load, and is expressed as a percent of rated output.

current

Flow of electrons past a point within a specified period of time, which is measured in amperes.

current loop

A current-based method of serial communications between digital devices where a logic "high" is represented by current flowing in the loop, and a logic "low" is represented by a lack of current flowing in the loop.

D

D (division)

Value of the smallest increment that is indicated (displayed) by a scale's divisions.

dash pot

A dampening device that is used to reduce scale oscillations.

dead load

The fixed force of load-supporting structures of the scale (like the weigh bridge or platform), the value of which needs to be permanently balanced or cancelled out in the weight or measuring system.

decimal point

Determines the location of the decimal point or number of dummy zeros for the graduation size. E.g., 8888.88 would have two places to the right of the decimal point, 888880 would have one dummy zero.

deflection

Change in length along the primary axis of the load cell between no-load and rated load conditions.

demand mode

Transmission of serial output data, which needs a manual "Print" command to initiate the output data. It is usually used to interface indicators to printers.

numerical digit

The smallest increment of weight that the indicator resolves.

digital

A system of signal representation that employs discrete values instead of continuously variable (analog) values.

digital averaging

A digital indicator's ability to smooth bouncy or erratic readings before sending the signal to the display, by taking several readings and averaging them together. Increasing the digital averaging slows the indicator's update rate.

digital filtering

Used to stabilize the readout of the indicator. More digital filtering applied leads to a more accurate display reading, but a longer settling time is required.

display divisions

Selects the minimum division size for the displayed weight of primary units, and determines if the count by will be 1, 2, or 5.

divisions

Determines the amount of increments in weight that a scale offers.

dormant scale

A built-in weighing scale with a self-contained understructure.

dot matrix

A method of printing where a rectangular array (matrix) of spaces is filled in to form alphanumeric and punctuation characters.

dribble

The weight value over which material is slowly handled to provide a more accurate cutoff in filling operations.

drift

A continuously upward or downward change in the number displayed on the digital readout, which could occur due to temperature, static electricity or radio frequency interference (RFI).

dropout

A temporary loss of electrical power, which is normally caused by break-before-make switching strategies used in utility and maintenance switching functions.

dual in-line package (DIP)

An integrated circuit contained within a standard housing characterized by its low profile, rectangular body, and symmetrical placement of leads along two opposing sides the device.

E

E (verification scale division)

Value of a verification scale division which sets the value for tolerances and accuracy class, as specified by the manufacturer.

E_min (minimum verification scale divisions)

The minimum scale division or value for which a device complies with applicable requirements, e.g., bench or counter scale. While given in proper form E_min, is it commonly also written "Emin" or "e-min". See also minimum verification interval (V_min)

eccentric load

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

electrical noise

Extraneous undesirable currents or voltages that interfere with desirable electrical quantities. Some causes are distant lightning, radio transmitters, welding equipment, electrical switching equipment, poor brush contact on motors, and other electronic devices utilizing switching power supplies.

electrically erasable programmable read-only memory (EEPROM)

A component of data storage where data can be repeatedly read out, stored data can be erased by an electrical signal and new data can then be programmed into the component.

electromagnetic interference (EMI)

Interference caused by electrical fields due to capacitive coupling, or magnetic fields due to mutual inductance of electromagnetic fields (radio waves).

electron

A negatively charged subatomic particle that orbits the nucleus of an atom. The flow of electrons determines electric current.

electrostatic charge

An electric charge on the surface of an insulated object.

electrostatic discharge (ESD)

A rapid discharge of an electrostatic potential, which can cause damage to integrated circuits.

environmentally protected

Load cells that feature a strain gauge cavity filled with a potting compound to protect them from normal environmental factors in indoor or outdoor applications. The cavity opening is also generally protected against physical damage, with loose-fitting side plates or molded plastic. These cells should not be submersed or washed down.

erasable programmable read-only memory (EPROM)

A component of data storage where data can be repeatedly read out, stored data can be erased by applying ultraviolet light and new data can then be programmed into the component.

error

The algebraic difference between the indicated and true value of the load being measured.

excitation

The voltage or current applied to the load cell's input terminals.

excitation trim

Method of adjusting the excitation voltage to each individual load cell in order to match load cell outputs in a multicell system. Adjustment is made by changing the setting of a variable resistor in series with the excitation input.

explosion-proof enclosure

An enclosure that is designed to withstand specified gas or vapor explosions which may occur within it, and to prevent the ignition of the gas surrounding the enclosure. It must also operate at an external temperature which makes it incapable of igniting its surrounding atmosphere.

F

Factory Mutual (FM) Approved

Symbol: FM inside a horizontal lozenge, above the word "APPROVED". Products displaying this symbol have been approved for use in hazardous (classified) locations, when proper installation procedures and drawings are followed, and intrinsic safety barriers are utilized. Named for the Factory Mutual insurance company, today FM Global.

ferrite core

(Also ferrite block, ferrite bead, ferrite ring, ferrite EMI filter, ferrite choke); a passive electric component used to suppress high frequency noise in electronic circuits.

filtering cutout sensitivity

Number of consecutive readings that must fall outside the filter threshold setting before filtering is suspended. If set to none, digital filtering is always enabled.

filtering threshold

Filter threshold in display divisions; filtering is suspended when a specified number of consecutive readings fall outside the threshold, which helps settling times when high filtering rates are used.

flexures

Thin steel or plastic bands or plates that replace the pivots and bearings of a conventional scale, which allow less movement and reduce friction.

fulcrum

A pivot point for a lever.

full duplex

Simultaneous, two-way, independent data transmission in both directions.

G

gated power supply

A power supply that allows conduction only when signal magnitude is within specified limits.

grad

Unit that specifies the number of full-scale graduations. Capacity = grads × count-by.

graduation

A mark on an instrument or vessel, used to indicate degrees or quantity.

H

half duplex

Data transmission in both directions, but not simultaneously. See full duplex.

Handbook 44

(Complete title: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices); a comprehensive set of requirements for weighing and measuring devices that are used in commerce and law enforcement activities; not a federal law, but developed and updated annually by the National Conference on Weights and Measures. Often abbreviated H-44.

handshaking

Exchange of predetermined signals between two devices, for the purpose of control and data exchange.

Hazardous location

Also hazardous-classified location or classified-hazardous location. A location where the presence of flammable gases or vapors, flammable liquids, combustible dust or easily ignitable fibers or flyings may cause fire or explosion hazards.

hermetically sealed

Load cells with a metallic protective cover that welded or soldered in place to protect the strain gauge cavity. Some cells have additional protection like glass-to-metal seals at the cable entry. These load cells provide the best possible protection in harsh chemical or washdown environments.

high-pass filter

A filter passing frequency that accepts components above a designated frequency and rejects components below that frequency.

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 by decreasing the load from rated load. To minimize creep, measurements should be taken as swiftly as possible.

hysteresis error

Different readings obtained for the same object.

I

influence factors

Environmental elements like temperature, humidity, radio frequency interference, barometric pressure and electric power, which may alter or interrupt an electronic or mechanical indication.

input/output (I/O)

Devices or circuits that allow a digital unit to send data (output) and receive data (input).

instability

The displayed number continues to vary randomly instead of progressively. See drift.

insulation resistance

The DC resistance measured between the load cell circuit and structure, which is normally measured at fifty volts DC and under standard test conditions.

interface

A device or circuit that allows communication between two units. Some of the standard interfaces used in the scale industry include 20 mA current loop, BCD, RS-232, RS-422 and RS-485.

internal resolution

Smallest increment of the A/D converter.

International Organization of Legal Metrology (OIML)

Treaty organization that recommends technical requirements for weighing and measuring equipment, before the sale or distribution of a model or type within the state, nation, etc. Abbreviated OIML from the French Organisation Internationale de Métrologie Légale .

international protection (IP) rating

ingress protection rating

A rating system that defines the protection of a product or enclosure against the ingress of solid objects and liquids. 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.

intrinsic safety barrier

A network that is designed to limit the energy (voltage and current) available to the protected circuit in a hazardous (classified) location, under specified fault conditions.

intrinsic safety ground bus

A grounding system with a dedicated conductor, which is separate from the power system so that ground currents will not normally flow, and reliably connected to a ground electrode in accordance with Article 200 of the NEC.

intrinsically safe circuit

A circuit in which the ignition of a mixture of flammable or combustible material in air cannot be caused by a spark or thermal effect, under prescribed test conditions in its most easily ignitable concentration.

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.

J

junction box

Also J-box. A box or enclosure that is used to join different runs of cable or wiring, which provides load cell trimming with space and terminals for connecting and branching the enclosed conductors and adjustments.

L

latch

To maintain a closed (energized) state in a pair of relay contacts after initial energization from a single electrical pulse.

latching relay

A relay which locks into the mode (on or off) for which it is energized, and requires a start-stop button. Once activated, it stays activated until the setpoint is reached or the stop button is pushed.

lever

A tool, often used with a fulcrum, that transfers force equally with reduction or multiplication.

light-emitting diode (LED)

A semiconductor light source that emits visible light or invisible infrared radiation.

linearity

The quality of delivering identical sensitivity throughout the weighing capacity of a scale or balance.

linearity calibration

A method that minimizes deviation between actual and displayed weights within the weighing range of the scale. It utilizes three calibration points, one at zero, center span and full span.

linearity test

A test that measures an instrument's ability to have consistent sensitivity throughout the weighing range.

liquid crystal display (LCD)

A thin, flat electronic visual display that uses the light modulating properties of liquid crystals (LCs), which do not emit light directly.

live load

The load applied to a scale base that is actually being measured by the weighing system.

structural load

The amount of weight or force that is applied to the load cell.

load cell

A device that produces an output signal which is proportional to the weight or force applied. Types of load cells include beam, S-beam, platform, compression and tension.

low-pass filter

A filter that passes frequency components below a designated frequency and rejects components above that frequency.

M

mass

The quantity of matter in a body, usually measured by weight.

megohmmeter

(Also megger); a special ohmmeter for measuring resistances in the megohm (106 ohms) range.

metal film resistor (MFR)

A fixed or variable resistor in which the resistance element is a thin or thick film of a metal alloy deposited on a substrate made of plastic or ceramic material.

metal oxide varistor (MOV)

A voltage-dependent resistor whose resistance predictably changes with voltage applied, and is used as a shunt protection device in transient protectors.

micro-

A prefix meaning millionths (10⁻⁶). Symbol: "m", used as a combining form only ("m" by itself means meter).

microvolts per graduation

The number of microvolts of live load signal that are needed to change the display.

minimum dead load

Specified for NTEP load cells. In a given application, the dead load applied to each cell must be greater than or equal to the minimum dead load as specified by the load cell manufacturer.

minimum verification interval (V_min)

A parameter used to select load cells for NTEP-approved applications. For single cell applications, V_min is "the smallest interval into which the load cell measuring range can be divided." Thus, it must be less than or equal to the scale division size. for mechanical scale conversions using one load cell, V_min must be less than or equal to the scale division size divided by the scale multiple. For a scale using more than one load cell, V_min must be less than or equal to the scale division divided by the square root of the number of cells. While given in proper form V_min, is it commonly also written "Vmin" or "v-min". See also E_min (minimum verification scale divisions).

minimum weight

The piece weight required in counting mode and normally used with counting scales.

motion band

Sets the level in display divisions that motion is detected. If motion is not detected for 1 second, the standstill annunciator lights. Certain functions like Tare, Zero, and Print are prohibited while the scale is in motion.

motion detection

A circuit that is used in an indicator to sense when displayed weight data is changing at a greater rate than preset limits (or is unstable), and to inhibit certain functions (like data output, entry of a push-button auto zero, entry of an auto tare value or activation of zero tracking) during this time.

N

nmax (maximum number of scale divisions)

The maximum number of scale divisions for which a product has been approved; must be greater than or equal to the number of divisions for which the scale will be configured.

National Conference on Weights and Measures (NCWM)

An association of state and local officials (federal and industry representatives) that adopt uniform (model) laws and regulations (e.g., NIST Handbook 44).

National Electrical Manufacturers Association (NEMA)

An association of electrical equipment and medical imaging manufacturers that develops standards for the electrical manufacturing industry.

National Institute for Standards and Technology (NIST)

(Formerly National Bureau of Standards (NBS), and an outgrowth of the Office of Weights and Measures; an agency of the federal government to which all precision measurements are traceable.

National Type Evaluation Program (NTEP)

A program of cooperation between the National Conference On Weights & Measures, NIST, state-level weights and measures officials, and the private sector, to determine conformance of weighing equipment with H-44 provisions.

National Type Evaluation Program Certificate of Conformance (NTEP CC)

Certification that a device meets all applicable requirements of Handbook 44. Informally abbreviated CC, but given in full form as NETP CC, followed by certification number.

negative logic

Binary logic in which a high negative state represents a "1" condition and a low negative state represents a "0" state.

negative value

After an item is removed from the scale, any tared value will be displayed as a negative number. See "tare".

nominal load capacity (NLC)

The designed normal maximum load cell capacity, on which output load cell sensitivity is based (unless otherwise specified).

non-latching relay (NLR)

A relay that will stay at the logic level based on the current setpoint data, and "toggle" from energized to de-energized states depending on the signal sent to it.

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-volatile memory

A computer storage medium whose contents do not change when the power is switched off, and are available when it is switched on again.

O

Office of Weights and Measures (OWM)

A government office that partnered with the National Conference on Weights and Measures (NCWM) to promote uniformity in weights-and-measures laws, regulations, metrology tests and standards, in order to achieve equity between buyers and sellers. It was a division of the US Coast and Geodetic Survey, until it separated to become today's National Institute of Standards and Technology (NIST).

ohm

The unit of electrical resistance, measured as the resistance through which a current of one ampere will flow when a voltage of one volt is applied.

Ohm's law

The relationship between current, voltage and resistance. Current varies directly with voltage, and inversely with resistance (I = E/R, where I = Current, E = Voltage and R = Resistance).

original equipment manufacturer (OEM)

A manufacturer who produces equipment that another manufacturer can use or include in its product.

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.

output, rated

The algebraic difference between the outputs at no-load and at rated load.

overload rating, safe

The maximum load which can be applied without producing a permanent shift in performance characteristics (beyond those specified), expressed in percent of rated capacity.

overload rating, ultimate

The maximum load which can be applied without producing a structural failure, expressed in percent of rated capacity.

P

parallel circuit

A circuit in which the components are connected across each other, and equal voltage is applied to each component.

parallel communications

Data communication type where all elements in an information item (bits in a word) are acted upon simultaneously, instead of one at a time (as in serial communications).

parity

A method of error checking where an extra bit is sent to establish an even or odd number of ones in the data of a character.

poise

A moveable weight that is used to counterbalance the load on a scale.

port

A point at which signals may be introduced to or extracted from a circuit, device, or system.

potentiometer

A variable resistor that is employed as a voltage divider.

potted cell

An environmentally-sealed load cell where the strain gauge cavity is filled with a material that protects the gauges from moisture and other environmental hazards. The potting material must not interfere with normal strain gauge movement, and must allow the gauges to return to their normal zero output position.

preact

Weight value which is set to allow for material in suspension during a filling operation.

pressurization

The process of supplying an enclosure with clean air or an inert gas, with or without continuous flow at sufficient pressure, to prevent the entrance of combustible dust.

primary axis

The axis along which the load cell is designed to be loaded, normally the geometric centerline of the load cell.

protective component

A component or assembly that is so unlikely to become defective (in a manner that will lower the intrinsic safety of the circuit), that it may be considered not subject to fault during analysis or tests for intrinsic safety.

purging

The process of supplying clean air or an inert gas in an enclosure, at sufficient flow and positive pressure to reduce the concentration of any flammable gases or vapors initially present (to an acceptable safe level), and to maintain this safe level by positive pressure with or without continuous flow.

push-button auto zero (PAZ)

Extension of a digital weight indicator's AZM function through the use of a front panel push-button.

R

raceway

An enclosed channel that is designed to hold wires, cables, or busbars.

radio frequency Interference (RFI)

Radio frequency energy of sufficient magnitude to possibly affect the operation of other electrical equipment.

rainproof

An enclosure that is constructed, protected, or treated, in order to prevent rain from interfering with the successful operation of the apparatus under specified test conditions.

raintight

An enclosure that is constructed or protected in a way that that exposure to a beating rain will not result in the entrance of water under specified test conditions.

random-access memory (RAM)

A data storage device that can be accessed in any order, known as a read/write memory since information can be written into it and then read out by the microprocessor when needed. Contents are lost when the system is powered down.

readability

Smallest division increments display.

reactance

The opposition offered to the flow of alternating current by pure capacitance, pure inductance, or a combination of the two. Measured in ohms.

read-only memory (ROM)

A memory unit in which information or instructions are permanently stored for use by the machine, or for reference by the user. Stored data is read out non-destructively and no information can subsequently be written into the memory.

reference standard

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

remote sensing

A method of regulating the excitation voltage to the load cells. Some indicators compensate for voltage drops that occur between the indicator and load cells by increasing the indicator excitation output voltage, others by amplifying the load cell return signal.

repeatability

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

resistance

Opposition to the current-flow that is offered by a purely resistive component; simple opposition to current flow. Measured in ohms. See also reactance; not to be confused with resistivity.

resistivity

The electrical resistance offered by a unit cube of material to the flow of direct current (DC) between opposite faces of the cube. Measured in ohm-centimeters. Not to be confused with resistance.

resolution

The smallest change in mechanical input that produces a detectable change in the output signal.

RS-232

A voltage-based serial method of data communication used to transfer data between digital devices. Two wires carry data; one wire is signal ground, and several control wires may be used for handshaking. A logic "high" is from -3 to -25 volts and a logic "low" is from +3 to +25 volts. Transmission distance should be restricted to 50 feet.

RS-422

A communication method that provides for data transmission using balanced or differential signaling, with unidirectional/non-eversible, terminated or non-terminated transmission lines, point to point, or multi-drop. In contrast to RS-485 (which is multi-point instead of multi-drop) RS-422 does not allow multiple drivers but only multiple receivers.

RS-485

A data communication method that can be effectively used in electrically noisy environments as well as over long distances. Multiple receivers may be connected in a linear, multi-drop configuration, which make these networks useful in industrial environments and similar applications.

S

safety factor

A figure denoting the overload (and allowance thereof) a device can withstand before breaking down.

sample rate

Measurement rate that the A/D converter updates, expressed in samples per second. Lower values are more immune to noise.

scale

A device that is used for weighing, comparing and determining the weight or mass of an object or material.

sense

Compensates for the resistance changes in the copper wiring, by comparing the supplied excitation voltage to the applied excitation voltage at the load cell.

sensitivity

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

sensitivity drift

A term used to express how temperature changes can affect the performance of the balance.

serial transmission

A data transmission method in which each bit of information is sent in a sequence on a single channel.

setpoint

In a feedback control loop, the point which determines the desired value of the quantity being controlled.

shear beam

A bending beam load cell, in which the strain gauges are mounted on a thin web of material in a machined-out cavity within the cell.

shield

A component used to protect the signal from RFI/EMI, which needs to be grounded at one end. The shield wire is not connected to the load cell housing, but terminates at the indicator instead.

shift test

A test intended to disclose the weighing performance of a scale under off-center loading.

side load

Any load acting 90° to the primary axis, at the point of axial load applications.

signal

The actual millivolt output of the load cell, with signal wires connected to the A/D of the indicator. It is here where the analog signal is converted to digital, and signal strength is expressed in microvolts per graduation.

signal in-line package (SIP)

A flat, molded component package with terminal lugs along one side; half of a dual in-line package (DIP).

signal trim

A method of matching load cell outputs in a multicell system, by adjusting the output signal voltage through a variable resistor placed across the signal leads.

span

The difference between the highest and lowest values.

span calibration

Utilizing two calibration points; one at zero and a choice of either half capacity or full capacity.

stabilization period

The time required to ensure that any further change in the parameter being measured is tolerable.

stack

A temporary storage area (consisting of a small group of registers) in a computer memory. Data stored in it is retrieved in reverse of the order in which it is stored.

standard test conditions

The environmental conditions under which measurements should be made, when measurements under any other conditions may result in disagreement between various observers at different times and places. These conditions are: Temperature: 72 degrees plus 3.6 degrees F (23 degrees plus or minus 2 degrees C), Barometric Pressure: 28 to 32 inches Hg.

static overload capacity

A percentage of nominal load limit capacity, up to which limit the load cell can safely be loaded without adverse effects on performance, or any change in its zero balance and other specifications.

stay rods

Rods installed to rigidly restrain a vessel or other weighing system component in the horizontal position, with little effect on the system's accuracy when they are installed properly.

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 that are cemented to the surface under test, and the wires stretch or compress as the surface becomes strained, changing their resistance. Several strain gauges are used to make up a load cell.

T

tare

The weight of an empty container or vehicle, or the allowance or deduction from gross weight made on account thereof (typically a compensating adjustment to a scale to return it to zero with the container on the scale).

temperature coefficient

A figure that states the extent to which a quantity drifts under the influence of temperature. voltage surge.

temperature effect, on rated output

The change in rated output caused by a change in ambient temperature, normally expressed as the percentage change in rated output per 100 °F change in ambient temperature.

temperature effect, on zero balance

The change in zero balance caused by a change in ambient temperature, normally expressed as the change in zero balance in percent of rated output per 100 °F change in ambient temperature.

temperature range, compensated

The range of temperatures over which a load cell is compensated to maintain rated output and zero balance, within specific limits.

temperature range, safe

The extremes of temperatures within which a load cell will operate without permanent adverse changes to any of its performance characteristics.

terminal resistance, corner-to-corner

The resistance of the load cell circuit, which is measured at specific adjacent bridge terminals at standard temperature with no load applied, and with open-circuited excitation and output terminals.

terminal resistance, input (excitation)

The resistance of the load cell circuit, which is measured at the excitation terminals at standard temperature with no load applied, and with open-circuited output (signal) terminals.

terminal resistance, output (signal)

The resistance of the load cell circuit, which is measured at the output signal terminals at standard temperature with no load applied, and with open-circuited excitation terminals.

tolerance

The amount of error that is allowed in a value, normally expressed as a percent of nominal value, plus or minus "x" measurement units.

traceability

The step-by-step transfer process by which the load cell calibration can be related to primary standards.

transducer

A piece of equipment that can convert energy from one form to another.

transient

A momentary surge on a signal or power line, which may produce false signals or triggering impulses, and cause insulation or component breakdowns and failures.

triac

A three-terminal silicon switching device that is gate controlled and bidirectional, which can switch either alternating or direct currents.

trim

To make a fine adjustment, such as in the outputs of load cells in a multicell system.

U

unit

The unit of measurement that is to be represented, e.g. lb., kg., oz.

Universal Serial Bus (USB)

A specification that is used to establish communication between various devices and a host controller (normally used for personal computers).

V

V_min (verification minimum)

See minimum verification interval.

volatile memory

A data storage component in computers, in which stored contents are lost when there is a loss of power.

volt

The unit of voltage, potential difference and electromotive force. One volt will send a current of one ampere through a resistance of one ohm.

voltage

The electrical potential difference that exists between two points, and is capable of producing a flow of current when a closed circuit is connected between the two points.

voltage dip

A temporary decrease in voltage level which lasts for at least one alternating current (AC) cycle.

voltage spike

A large and destructive voltage pulse caused by lightning strikes on a power line, communication line, signal or sensing line, or even nearby ground.

voltage surge

A temporary rise in voltage level which lasts for at least one alternating current (AC) cycle.

W

water-pipe ground

An earth connection that is made by running a strong wire to the nearest cold water pipe.

watertight

An enclosure that is constructed in a manner that prevents moisture from entering it under specified test conditions.

weatherproof

An enclosure that is constructed or protected in a manner that exposure to the weather will not interfere with the successful operation of the equipment it contains.

weight

The amount of force or gravitational pull by which an object or body is attracted toward the center of the earth.

Z

Zener diode

A semiconductor diode which is used in the reverse biased condition. It exhibits a nondestructive breakdown at a predetermined reverse voltage, so an increase in current flow through the diode will not result in increased voltage drop across it, while operating in this breakdown region. It is used in voltage regulation circuits and in intrinsic safety barriers, as a device to limit voltage.

zero balance

The output signal of the load cell with rated excitation and with no load applied, normally expressed in percent of rated output.

zero function

By pressing the tare key, the scale display returns to zero.

zero range

This is the range in which the scale can be zeroed. A selection of 1.9% means that the scale will zero off any weight within + or − 1.9% of the calibrated zero point.

zero return

The difference in zero balance, which is measured 1) immediately before rated load application of specified duration, 2) after removal of the load, and 3) when the output has stabilized.

zero shift, permanent

A permanent change in no-load output.

zero stability

The degree to which the load cell is able to maintain its zero balance, with all environmental conditions and other variables remaining constant.

zero-track band

Automatically zeroes off the scale within the specified range, and is most often used to zero off the buildup of water, ice, and snow on a scale.