Page 9
IronHorse GSDA-CM-8 User Manual – 1st Ed. Rev. A – 10/15/19
NOTE: If the analog input is assigned to a function that can also be controlled from the front panel
of the GSD8 drive or with serial communications messages, then any of those sources can change the
value associated with that function. The value of that function will be the value written most recently
from any source that has access to it. This flexibility should be considered when designing the system
in which the GSD8 drive will be used. Reference the manual for the “Program Enable Jumper”, JP1,
for details on how to lock-out functions so that they cannot be changed from the GSD8 front panel.
WARNING: W
heN
AN
ANAloG
INput
souRce
type
Is
coNfIGuRed
As
“m
AIN
t
Ach
”
oR
“l
eAdeR
t
Ach
”
sIGNAl
; do Not
coNNect
A
sIGNAl
souRce
to
the
Gsd8
teRmINAl
stRIp
,
teRmINAl
p1-7. c
oNNectIoN
to
thIs
teRmINAl
WIll
Not
dAmAGe
the
Gsd8
dRIve
,
but
It
WIll
leAd
to
uNpRedIctAble
Results
due
to
the
secoNd
sIGNAl
.
Analog Source Signal Configuration
Configuring the GSD8 drive to use the analog source signal involves several steps; these are:
•
Analog Source Signal Destination
•
Analog Source Signal Type
•
Analog Source Signal Minimum Value
•
Analog Source Signal Maximum Value
Minimum Value:
“Minimum Value” refers to the lowest scaled value produced by the GSDA-CM-8, A to D converter when
the analog source signal is at the lowest value.
•
For a potentiometer source signal, minimum value occurs with the potentiometer wiper at the closest
position to the potentiometer terminal connected to the GSDA-CM-8, signal common; resulting in
zero volts on the wiper.
•
For a voltage source signal, minimum value equates to zero volts when measured between the analog
voltage source and signal common.
•
For current sources, the minimum value is obtained with a current of 4mA or less.
Maximum Value:
“Maximum Value” refers to the highest scaled value produced by the GSDA-CM-8, A to D converter
when the analog source signal is at the highest or most positive value.
•
For a potentiometer source signal, maximum value occurs with the potentiometer wiper at the closest
position to the potentiometer terminal connected to the GSDA-CM-8, +5VDC connection; resulting in
+5 volts on the wiper.
•
For voltage sources, that means +5VDC measured between the analog input and signal common.
•
For current sources, the maximum value is obtained with a current of 20mA.
Setting Minimum and Maximum Values
Analog input signals are typically scaled to engineering units that correspond to the engineering range
of the signal.
Analog input signal resolution is a function of the A/D converter in the GSDA-CM-8 and that resolution
varies depending on whether the analog input is a voltage or milliamp signal. For potentiometer and
voltage sources, resolution is 1024 parts. For current source signals (4 to 20mA), resolution is 810
parts.
Resolution determines the smallest amount of change that can be processed by the A/D converter and
as a result how closely the analog signal can be tracked.
For example, an analog input signal in the range of 0 to 5 VDC has a span of 5 volts, that span is divided
into 1024 parts or counts by the A/D converter. Therefore, the A/D converter will process digital values
equivalent to 0.00488 volts per count.
Applying an engineering range to the signal provides both the “Minimum Numeric Value” (parameter
42) and the “Maximimum Numeric Value” (parameter 43) that will be produced as a result of the A/D
conversion.
If in this example the “Minimum Numeric Value” is zero (0) and the “Maximum Numeric Value” is 1000,
then the A/D converter will produce the numeric value zero (0) with an analog input voltage of zero
volts and a numeric value of 1000 with an analog input voltage of 5 volts.
