Technical Notes - Signal Conditioners, Transmitters, Isolators, & Signal Convereters

DEFINITION
Deadband is the range through which an input can be varied without initiating an observable response.
Deadband is usually expressed in percent of span.

EXAMPLE
A 20% total deadband is applied to the setpoint of a monitored parameter. The relay will trip and reset to its untripped state as indicated in the following graph.

Accuracy: The closeness of an indication or reading of a measurement
device to the actual value of the quantity being measured. Accuracy calculations
are based on the linearity, hysteresis, and repeatability characteristics of
the transducer/sensor and supporting electronics, the range of the transducer/
sensor, as well as the resolution being displayed. It is usually expressed as
a ±% of full scale output of the transducer/sensor/system.

In a process control loop, a ground loop circuit can develop when each device's ground is tied to a different earth potential thereby allowing current to flow between the grounds by way of the process loop (Figure 1). Ground loops cause problems by adding or subtracting current or voltage from the process loop. This addition and/or subtraction causes the receiving device to be unable to differentiate between the wanted and unwanted signals and thus can't accurately reflect actual process signals.