User Manual V 1-4.XX User guide

Applications 9-9
To calibrate the pot to control 100% base speed in both directions,
you need to adjust the scale parameter. The default value of the scale
parameter 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 An In 2 Scale (parameter 101), the digital input is multiplied by 2.
This provides a range of ±4096, or 100% base speed in both
directions.
If you want a range of ± 2 times base speed, the scale factor would be
4 (base speed is 4096, 2 times base speed is 8192, 2048 times 4 is
8192). An In 2 Offset (parameter 100) remains at the default value of
zero, allowing the input range to be ±10V. The range of the offset
parameter is ± 20V DC as shown in Figure 9.2.
In this example, the filter parameter, An In2 Filter BW
(parameter 183), is not used. The filter parameter is a low pass filter
that helps to reduce the affects of noise on the system.
Figure 9.2
Potentiometer with +10V Range to Control 0 to +100% Base Speed
For a second example, a 0 to 10 volt potentiometer adjusts the torque
reference from -100% to +100%. To do this, you need to adjust both
the scale and offset parameters. By linking An In 1 Value
(parameter 96) to Torque Ref 1 (parameter 69), the potentiometer
connected to analog input 1 becomes the torque reference signal. This
signal must be scaled and offset to get the entire ±100% in the 0 to 10
volt range. A digital range of 8192 (±4096) must now be scaled for an
analog range of 10 volts, and must be offset so 5 volts on the
potentiometer indicates 0% torque.
As shown in Figure 9.3 the offset voltage adds the corresponding
digital value to the range. In this case, an offset of -5 volts adds a
digital value of -1024 to the range. This causes 0 volts on the
potentiometer to register as -1024 digital internal to the drive and 10
volts on the potentiometer is +1024 to the drive. This can then be
scaled by a factor of 4 (8192 drive units) so that 0 volts sends a digital
value of -4096 for -100% torque, and 10 volts sends a digital value of
+4096 for +100% torque.
10V Pot
0
–10V
Multiplexer
A
D
An In 2 Scale
Par 99
+2048
0
–2048
+2048
0
–2048
+4096
0
±4096
Range of 20V
0
0
0
0
–10V
–2048
X 2
–4096
+10V
+2048
X 2
+4096
Par 101
X 2
+
+10V
Par 36
+ 2048
(=
± 10V)
An In 2 Offset
Par 100 = 0
Potentiometer
Digital Value
Scale
Final Value in Par 99
An In 2 Value
Speed
Ref 7
An In2 Filter BW
Par 183
0