Chapter 1. Calibration
6 DigitalFlow™ GF868 Service Manual (1 and 2-Channel)
1.4 Calibrating the Analog Inputs
Analog inputs may be added to the Model GF868 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 will be 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 3. Refer to the menu map in Figure 6 on page 15 as a guide.
Figure 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)
RTNSIG
BB
SIG
AA
1
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