17. GLOSSARY OF TERMS
Adaptive Filter Threshold
A threshold which causes an adaptive moving average filter to be reset to the
latest reading when the accumulated difference between individual readings
and the filtered reading exceeds that threshold. Adaptive moving average
filtering allows a meter to respond rapidly to actual changes in signal while
filtering out normal noise.
Alarm, Latched
An alarm that stays actuated until reset. Latched alarms can maintain a shut-
down condition or maintain an alarm until acknowledged by an operator.
Alarm, Non-latched
An alarm which changes state automatically when the reading rises above a
specified limit and changes back automatically when the reading falls below a
limit. Also called “Auto Reset.”
Auto-filter A selectable digital filter mode that automatically selects an appropriate moving
average filter time constant for the encountered noise condition.
Batch Average Filter
A digital filter mode where readings are the displayed average of 16 conver-
sions. Conversions are made at 60/second in a 60 Hz environment and
50/second in a 50 Hz environment.
Deviation Band
A value which controls relay action symmetrically around a setpoint. The relay
activates when the reading falls within the deviation band, and de-activates
when the reading falls outside. A deviation value (e.g., 50 counts) is set up
around both sides of the setpoint to create a deviation band or pass band (e.g.,
100 counts), which equals two deviation values.
First Peak The first maximum (or most positive) reading followed by a decrease of a
selectable percentage Full Scale since that maximum was last reset.
Full Scale The reading range equal to Hi Rd - Lo Rd.
Hysteresis A value which controls relay action symmetrically around a setpoint. The relay
closes (or opens) when the reading goes above the setpoint plus the hysteresis
value, and opens (or closes) when the reading falls below the setpoint less the
hysteresis value. A narrow hysteresis band is often used to minimize relay
chatter around a setpoint due to electrical noise or signal feedback caused by
load switching. A wide hysteresis band can be used for control applications.
The hysteresis band equals two hysteresis values.
Moving Average Filter
A digital filter mode that displays a weighting moving average of readings.
Readings are taken at 60/second in a 60 Hz power environment and 50/second
in a 50 Hz power environment. Display update rates remain at 3.75/second at
60 Hz and 3.13/second at 50 Hz. There are eight moving average modes:
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