Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 122)

Programming
Chapter 3
3Ć79
W32(W51), respectively. The negative sign of SMIN is set by
W30(W50) B04 = 1.
Table 3.N
Scaling With Negative SMIN
Analog
Signal
Actual
Flow Rate
W65 READ PV1
Without Scaling
W65 READ PV1
With Scaling
+20mA +60C 4095 60
+16mA +40C 3072 40
+12mA +20C 2048 20
+ 8mA 0C 1024 0
+ 4mA Ć20 o C 0000 20 [1]
no scaling scaling
W30 B17=0 W30 B17 = 1
SMIN W31 = 20
W30 B04 = 1 [2]
SMAX W32 = 60
W30 B03 = 0
[1]
W6 B16 must be read to determine the signed of the scaled value in word W65.
In this case, W61 B16=1 indicates a negative value.
[2]
When the minimum scaling sign bit W30 B04=1, the minimum scaling value in
W31 is negative.
Digital Filtering
Although not an expanded feature, digital filtering can be applied to
analog input signals to reduce the effects of electrical noise. Digital
filtering is done by a weighted moving average technique (Figure 3.23).
The digital filter equation (Figure 3.24) uses the input filter time TA
stored in word W20(W40).