Model 8712C/U/H Magnetic Flowmeter Transmitters
4-14
Control Status
The operating mode allows the user to choose the mode of operation
based on output stability.
Normal Mode
The normal mode uses 6 Hz coil drive mode and does not use the signal
processing. Normal mode is usually sufficient and should be used
whenever possible.
Filter Mode
The filter mode should be used only when the signal is noisy and gives
an unstable output. Filter mode automatically uses 30 Hz coil drive
mode and activates signal processing at the factory set default values.
When using filter mode, perform an auto zero, described on page 4-5
Either of the parameters, coil drive mode, or signal processing, may still
be changed individually.
Turning signal processing off or changing the coil pulse mode to 6 Hz
will automatically change the operating mode from filter mode to
normal mode.
Signal Processing Control
On/Off
When ON is selected, the Model 8712C/U/H output is derived using a
running average of the individual flow inputs. Signal processing is a
software algorithm that examines the quality of the electrode signal
against user-specified tolerances. This average is updated at the rate of
12 samples per second regardless of the selected coil drive mode. The
three parameters that make up signal processing (number of samples,
maximum percent limit, and time limit) are described below.
Number of Samples
0 to 125 Samples
The number of samples function sets the number of previous inputs
used to calculate the average value. Because the output stage of the
Model 8712C/U/H circuit is updated twelve times each second,
regardless of 6 or 30 Hz coil drive mode, the factory preset value of 90
samples equates to 7.5 seconds.
For example, if you select a sample number of 120, the response time of
the system will be 10 seconds (120 samples / 12 samples per second). A
suggested nominal number of 90 samples is a good starting point for
most applicable process fluids.
HART Fast Keys 1, 4, 4, 4
LOI Key Aux. Function
HART Fast Keys 1, 4, 4
LOI Key Aux. Function
HART Fast Keys 1, 4, 4, 5
LOI Key Aux. Function
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