Tek-Trol Tek-LCD 7802A, Instruction Manual, Page: 35 / 43

4.5.11 Low-Flow Cutoff (
CUTOFF
)
The low-flow cutoff feature allows the meter to be programmed so that the often unsteady output
from a differential pressure transmitter, at low flow rates, always displays zero on the meter. The
default cutoff is zero to prevent negative readings, but this may be overridden to allow them.
The cutoff value may be programmed from -0 to 99999. Below the cutoff value, the meter will
display zero. Selecting either square root or programmable exponent will set the cutoff value to 0.
Program the cutoff value to 0 to disable.
4.5.12 Input Signal Filter (
FILTER
)
The noise filter is available for unusually noisy signals that cause an unstable process variable
display. The noise filter averages the input signal over a certain period. The filter level can be set to
low
(
LO), medium (
m
Ed), high (HI), or off (OFF). The higher the filter setting, the longer the averaging
time and so the longer the display may take to find its final value.
The filter contains a noise filter bypass feature so that while small variations in the signal will be
filtered out, large, abrupt changes to the input signal are displayed immediately.
4.5.13 Internal Calibration (
ICAL
)
The noise filter is available for unusually noisy signals that cause an unstable process variable
display. The noise filter averages the input signal over a certain period. The filter level can be set to
low
( LO), medium (
m
Ed), high (HI), or off (OFF). The higher the filter setting, the longer the averaging
time and so the longer the display may take to find its final value.
The filter contains a noise filter bypass feature so that while small variations in the signal will be
filtered out, large, abrupt changes to the input signal are displayed immediately.
The internal calibration allows the user to scale the meter without applying a signal. The use of a
calibrated signal source is necessary to perform the internal calibration of the meter. Check
calibration of the meter at least every 12 months.
NOTE
The signal source must have a full-scale accuracy of 0.002% or better between 4 and
20 mA in order to maintain the specified accuracy of the meter.
Allow the meter to warm up for at least 15 minutes before performing the internal
calibration procedure.
There is no need to recalibrate the meter for milliamps when first received from the
factory.
The meter is
factory calibrated for milliamps prior to shipment. The calibration equipment
is certified to NIST standards.