Watlow ANASOFT - Manual (Page 77)

Appendix B: Input Scaling
ANASOFT User’s Guide 67
Appendix B: Input Scaling
All inputs use the automatic scaling function of the Mx+B calculation.
The end points of that calculation are set by HiPV, LoPV, HiRDG, and
LoRDG. The default values are set by the input Type selection. Do not
adjust these values until you completely understand what those
adjustments will do.
The T/C and RTD ranges are set in the firmware, and you don’t need to
adjust those ranges for a proper operating hardware or software. The
default values provide correct operating parameters as to stated
accuracy, PID control and Alarm settings.
For Linear inputs the scaling of the input is required to obtain correct
engineering units of the input. This must be done before setting SP, PB,
and Alarm settings.
Linear Input Scaling
A linear input of 60 mv or less is scaled according to the engineering
unit and mv range of the input signal. Watlow-Anafaze controllers have
a -10 to 60 mvdc analog input range. All linear inputs must be scaled to
that range by scaling resistors on the input.
The HiPV and LoPV is the range of the engineering unit, while the
HiRDG is the % of the Hi end signal level mv with reference to 60 mv
and the LoRDG is the % of the Lo end signal level with reference to 60
mv. The % is expressed as 1000 equals 100.0. Thus 83.3% would be set
as 833 on the RDG scaling.
Example 1:
The input signal is 4-20 madc representing a range of 0-250 PSI. The
scaling resistor is 3 ohms, thus full scale reading of the 20 madc signal
would be 60 mv. The Lo end signal of 4 ma would give a reading of 12
mv.
60 mv input of 60 mv range = 100%
12 mv input of 60 mv range = 20%
HiPV = 250
HiRDG = 1000(100.0)
LoPV = 0
LoRDG = 200(20.0)