GE AquaTrans AT868, User Manual

Page: 68 / 158

Calibration 4-1
September 2004
Introduction
Use this menu to calibrate and test the analog and totalizer/frequency
outputs. Refer to Figure A-4 on page A-4 in Appendix A,
Menu
Maps , while following the calibration instructions.
Calibrating and Testing
Analog Outputs
The Model AT868 flowmeter includes one built-in analog output per
channel with a resolution of 5.0
µ
A (0.03% full scale). Although one
analog output is provided for each channel, the outputs are channel
independent. Typically Output A is used for Channel 1 and Output C
is used for Channel 2; however, analog outputs can be configured to
measure either channel.
Both the zero-point and full-scale values for these outputs must be
calibrated. Once they are calibrated, the linearity should be tested.
Note:
The zero point of the analog output may be set for either 0 mA
or 4 mA. However, the calibration procedure always uses the
4 mA point, as the meter will extrapolate this value to obtain
the 0 mA point.
Preparing for Calibration
Prepare for calibration by inserting an ammeter in series with the load
on analog output 1 or 2 as shown in Figure 4-1 below.
DO NOT
connect the ammeter directly across the terminals. Refer to Figure 1-4
on page 1-16 for the locations of the analog outputs terminal blocks.
Note:
Analog outputs 1 and 2 in the wiring diagram correspond to
analog outputs A and C in the AT868 software.
Figure 4-1: Ammeter Connection
Ammeter
Load
AOUT1
FREQ1