GE DigitalFlow GC868, Service Manual

Page: 13 / 75

April 2008
1-6 Calibration
Calibrating the Analog
Inputs
Analog inputs may be added to the Model GC868 flowmeter by
installing an
Analog Inputs Option Card in one (or more) of the six
expansion slots. The option card contains two analog inputs, which
are designated as A and B. Each of the inputs, which may be either a
0/4-20 mA input or an RTD input, must be calibrated at both the zero-
point and full-scale values. After calibrating the inputs, their linearity
should be tested.
Calibration of the analog inputs requires the use of a calibrated
current source. If an independent calibrated current source is not
available, one of the
Slot 0
analog outputs may be used for the
calibration. During the analog input calibration, the
Slot 0
analog
output will supply the low reference, high reference, 4 mA and 20
mA signals at the appropriate times.
Note:
If a
Slot 0
analog output is used to calibrate the analog inputs,
make sure that the
Slot 0
analog output calibration procedure
has already been completed.
Connect the
Slot 0
analog output(s) (or an independent calibrated
current source) to the analog input(s) on the option card, as shown in
Figure 1-3 below. Refer to the menu map in Figure 1-6 on page 1-15
as a guide.
Figure 1-3: Analog Input Calibration Connections
Analog Input Option Card
A
INHI
A
+24V
A
RTN
A
INLO
B
RTN
B
INLO
B
INHI
B
+24V
1
8
RTN
4
Terminal Block I/O (Slot 0)
RTN SIG
B B
SIG
A A
1