Glossary of Technical Terms

To help put you in control, FAST provides you with the following glossary that will help you make the right decision when choosing our temperature controllers for your applications. 

A

AC (Alternating Current)
An electrical current that reverses its direction at regularly recurring intervals.

Accuracy
Conformity of an indicated value to an accepted standard value. It is the limit of error which the  controller can introduce into a control loop.

AGA
American Gas Association

Ambient Temperature
Temperature of the environment in which the device is located.

Ampere
A unit of electrical current equal to a current producing one volt applied across a resistance of one ohm.

B  

Bandwidth
Total overshoot (maximum) and undershoot (minimum) temperatures between set- point, often referred to as amplitude, or differential span.

Bias
An adjustable level of the minimum signal for start up, lift off point, or zero reference of the controller.

Cold Junction Compensation
Cold junction compensation eliminates error in sensor signal caused by ambient temperature changes at the sensor termination point. Normally the effect is found only with thermocouple sensors

Contactor
Electromechanical device capable of switch hi-amperage loads. A contactor is a relay with hi-current contacts.

Controller
A device which operates automatically to regulate a controlled variable.

Direct Acting controller output turns “off” as the system temperature increases above the set- point. Heating applications use a direct acting controller.

Reverse Acting controller output turns “on” as the system temperature exceeds the set point. Cooling applications use a reverse acting controller.

On-off (two position) controller has two discrete values of output: full on or full off.

D

db
Abbreviation for decibel, a unit for the logarithmic expression of ratios of power, voltage or current.

DC (Direct Current)
Electrical current that flows in one direction at a constant value.

Dead band
The range through which the measured signal can be varied without initiating a response. Also differential and neutral zone.

Differential Span
The total envelope of temperature excursion above and below the setpoint temperature. Also
described as bandwidth.

Duty Cycle
“on” cycles vs. “off’ cycles within the repetition rate.