Tp1 - Emerson Rosemount 8600 Series Reference Manual

Troubleshooting
May 2019
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
Verification.
To verify the electronics, you can input a frequency on the "TEST FREQ IN" and "GROUND"
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 Handheld
Communicator or AMS interface are required.
it flows from the sensor to the microprocessor in the electronics.
Figure 5-2. Signal Flow
Sensor
External Test
Frequency
Input
5.3.3

TP1

TP1 is the vortex shedding signal after it has gone through the charge amplifier and low pass filter
stages and into the input of the sigma delta A-to-D converter ASIC in the electronics. The signal
strength at this point will be in the mV to Volt range.
TP1 is easily measured with standard equipment.
Figures 5-3, 5-4, and
output to be inaccurate. Please consult the factory if the waveform you detect is not similar
in principle to these waveforms.
Figure 5-3. Clean Signals
0
3.0 V
0
A. Vortex signal (TP1)
B. Trigger level
C. Shedding frequency output
70
TP1
Charge
Amplifier/L
Amplifier
ow Pass
Filter
5-5 show ideal (clean) waveforms and waveforms that may cause the
Appendix C: Electronics
Figure 5-2 is a block diagram of the signal as
A-to-D
Converter
Internal
Digital Filter
Frequency
Generator
A
B
C
Rosemount 8600 Vortex Flow Meter
Reference Manual
00809-0100-4860, Rev BF
Microprocessor