Glossary of terms
4-20 mA loop A 4-20 mA signal that is representative of a process variable or a control
signal that controls a process variable.
Compliance voltage The voltage a current source develops when attempting to drive a mA
signal through a resistive load.
DMM Digital multimeter.
Electronic valve positioners Devices that can control the flow in a process with input from a mA or
digital control signal.
Ground loop A difference in potential (voltage) between (2) signal grounds.
Linearity The closeness of a calibration curve to a specified straight line. Linearity
is expressed as the maximum deviation of any calibration point from a
specified straight line.
Loop-powered isolator A device that produces an electrically isolated mirror image of the input
side 4-20 mA current.
mA Milliamp; a unit of electric current equal to one thousandth of an ampere.
Precision current shunt A conductor joining two points in a circuit to form a parallel circuit,
through which a precision voltage can be measured or derived.
RTD Resistance temperature device, a temperature measurement sensor that
has predictable changes in resistance with a change in temperature.
Signal conditioner A circuit to modulate a signal so as to make it intelligible to, or compati-
ble with, another device, including such manipulation as pulse shaping,
pulse clipping, compensating, digitizing, and linearizing.
Strain gauge A measuring element for converting force, pressure, tension, etc., into an
electrical signal.
Thermocouple A junction of dissimilar metals that generates a small voltage correlated
to the temperature of the junction.
µA or uA Microamp; a unit of electric current equal to one millionth of an ampere.
Vernier A small, movable, graduated scale running parallel to the fixed graduated
scale and used for measuring a fractional part of one of the divisions of
the fixed scale.
Fluke Corporation
PO Box 9090, Everett, WA USA 98206
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
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Fax (905) 890-6866
Other countries (425) 446-5500 or
Fax (425) 446-5116
Web access: http://www.fluke.com
©2001 Fluke Corporation. All rights reserved.
Trademarks are the property of their respective owners.
Printed in U.S.A. 8/2001 1627722 A-ENG-N Rev A
Printed on recycled paper.
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