Rockwell Automation 1395 Discrete Adapter, Rev 3.XX-8.XX User Manual
Page 28
Chapter 5
StartĆUp
5-5
Analog Input 1 and Analog Input 2 will be used in detailing the scaling and
offset parameters. At Analog Input 1, between TB3 terminals 29 and 30, a
potentiometer with a range of
±
10 V DC has been connected. Parameter
401 has been linked to Parameter 154 (Velocity Reference) in the drive,
which gives the potentiometer control of the external velocity reference. To
calibrate the pot to control 100% base speed in both directions, the scaling
parameter must be adjusted. The default value of the scale parameters
allows a total range of 4096, –2048 to +2048. This allows only 50% base
speed in each direction. By setting a scale factor of 2 in Parameter 550, the
digital input is multiplied by 2, providing a range of –4096 to +4096, or
100% base speed in both directions. If the user wanted a range of
±
2 times
base speed, the scale factor would have to be 4 (Base Speed = 4096, 2
times Base Speed = 8192, 2048 times 4 = 8192). Parameter 551, Offset,
will remain at the default value of zero, allowing the input range to be
–10V to +10V. The range of the offset parameter is
±
20VDC ( Figure 5.2).
Figure 5.2
Example: Potentiometer
±
10V Range to Control 0 to
±
100% Base Speed
+/- 10V
Pot
+10V
0
-10V
Multiplexer
A
D
+/- 2048
Scale
To P401
+2048
0
-2048
+2048
0
-2048
+4096
0
-4096
Offset
P551 = 0
Range of 20V
0
0
0
0
-10V
-2048
X2
-4096
+10V
+2048
X2
+4096
Potentiometer
Digital Value
Scale
Final Value P401
P550
X 2
For Analog Input 2, a 0 to 10 volt potentiometer will be used to adjust the
Torque Reference from –100% to +100%. To accomplish this, both the
scale and offset parameters will need to be adjusted. By linking Parameter
402 to Parameter 157, Torque Reference, the potentiometer connected to
Analog Input 2 becomes the Torque Reference Signal. This signal must be
scaled and offset in order to get the entire
±
100% in the 0 – 10 volt range.
A digital range of 8192 must now be scaled for an analog range of 10 volts,
and must be offset so 5 volts on the potentiometer will indicate 0% Torque.