Watlow CAS - Manual (Page 66)

56 CAS User’s Guide
Setup
Low Reading
This menu appears under the Setup Channel Inputs main menu. Use it to
enter the input level that corresponds to the low process value you
selected in the previous menu. For linear inputs, the low reading is a
percentage of the full scale input range; for pulse inputs, the low reading
is expressed in Hz. The full input range for the linear input type is -10 to
60 mV. For pulse inputs, it is 0 to 2000 Hz.
Selectable values: -99.9 to 999.9
Input Filter
The CAS has two different types of input filter:
• A noise rejection filter that rejects high frequency input signal noise.
This filter keeps a "trend log" of input readings. If a reading is out-
side the filter's "acceptance band", and later readings are within the
acceptance band, the CAS ignores the anomalous reading. (The
acceptance band for thermocouples is 5 degrees above and 5 degrees
below the input reading. For linear inputs, it's 0.5% above and 0.5%
below the input reading.) If later readings are also outside the accep-
tance band, the CAS accepts the anomalous reading and calculates a
new acceptance band. (You cannot adjust this input filter.)
• A standard resistor-capacitor (RC) filter that lets you dampen the
input response if inputs change unrealistically or change faster than
the system can respond. If the input filter is enabled, the process
variable responds to a step change by going to 2/3 of the actual value
within the number of scans you set.
If all input channels are enabled, none of them set to SKIP, the CAS will
scan 1.5 channels per second when set to 1 scan, and 4.5 channels per
second when set to 3 scans.
Selectable values: 0 to 255 scans
CHANNEL PROCESS UNITS
CHANNEL NAME ALARM STATUS
01 INPUT SCALING
LO RDG ? 0.0% FS
CHANNEL PROCESS UNITS
CHANNEL NAME ALARM STATUS
01 INPUT FILTER ?
3 SCANS