Chapter 4
Startup
4–24
A 10V Input and a Pot Input will be used in detailing the scaling and offset
parameters. At Pot Input, between TB5 terminals 7 and 8, a potentiometer
with a range of ±10V
DC has been connected. Parameter 358 has been linked
to Parameter 104 (Velocity Reference 2 HI) 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 360 (An In 1 Scale) 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 359 (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 ± 20V
DC as shown in Figure 4.8.
Figure 4.8.
Potentiometer with a +10V Range to Control 0 to +100% Base Speed
10V POT
0
–10V
A
D
SCALE
+2048
0
–2048
+2048
0
–2048
+4096
0
–4096
OFFSET
PAR 359 = 0
RANGE OF 20V
0
0
0
0
–10V
–2048
X 2
–4096
+10V
+2048
X 2
+4096
PAR 360
X 2
±
+10V
POTENTIOMETER
DIGITAL VALUE
SCALE
FINAL VALUE PAR 401
PAR 104
± 2048
(= ±
10V)
Par 358
Pot Input
VELOCITY
REFERENCE 2
HI
MULTIPLEXER
For 10V Input, 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 355 to
Parameter 162, Torque Reference, the potentiometer connected to Analog
Input 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 (± 4096) 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.
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