Emerson 8800A, Product Manual

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Rosemount Model 8800C Vortex Flowmeter
4-6
ADVANCED
TROUBLESHOOTING
The Model 8800C electronics provides several advanced
troubleshooting features. These features enhance your ability to look
inside the electronics and can be helpful for troubleshooting inaccurate
readings. As shown in Figure 4-1, there are several test points located
on the electronics.
Figure 4-1. Electronics Test Points
A digital representation of the filtered sensor shedding frequency is
available on the “SHEDDING FREQ OUT” pins shown in Figure 4-1.
The electronics are capable of internally generating a flow signal that
may be used to simulate a sensor signal to perform electronics
verification with the Model 275 or AMS interface. The simulated signal
amplitude is based on the transmitter required minimum process
density. The signal being simulated can be one of several profiles – a
simulated signal of constant frequency or a simulated signal
representative of a ramping flow rate. The electronics verification
procedure is described in detail in Appendix E: Electronics Verification.
To verify the electronics, you can input a frequency on the “TEST FREQ
IN” and “GND” pins to simulate flow via an external signal source such
as a frequency generator. To analyze and/or troubleshoot the
electronics, an oscilloscope (set for AC coupling) and a Model 275 or
AMS interface are required. Figure 4-2 is a block diagram of the signal
as it flows from the sensor to the microprocessor in the electronics.
8
8
0
0
-00
00
A
0
4C
Shedding Freq Out
GND
TP1
Test Freq IN