# Glossary of Loop Calibration Terms

Calibration
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

### 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 compatible 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.

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