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# Glossary of Loop Calibration Terms

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### 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.

## Glossaries

DMM products glossary »
Electrical glossary »
Pressure calibration terminology »
Temperature calibration terminology »
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