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CiDRA Use of Foundation Fieldbus Protocol with SONARtrac Transmitters User Manual

Page 20

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Table 3 Transducer Block Configurations (Page 7)

FLOW_NYQUIST_HIGH Float

R/W

Define high end of frequency range to use for
determining flow velocity. Defined by:
FREQUENCY_MAX = (Measured Velocity *
VF_NYQUIST_HIGH) / Sensor Spacing. Example: (10
ft/sec*0.7) / 0.2 = 35Hz

FLOW_NYQUIST_LOW Float

R/W

Define low end of frequency range to use for
determining flow velocity. Defined by:
FREQUENCY_MIN = (Measured Velocity *
VF_NYQUIST_LOW) / Sensor Spacing. Example: (10
ft/sec*0.3) / 0.2 = 15Hz

FLOW_CENTROID_WIDTH Float

R/W

Define width of peak to use in calculation of flow rate.

FLOW_VEL_SEARCH_LIMIT_LOW Float

R/W

Define low end of velocity search range to use for
determining flow velocity. Defined by: Velocity_Min =
(FREQ_MAX * Sensor Spacing) /
VF_SEARCH_LIMIT_LOW. Example: at 10ft/sec* (10
ft/sec*0.7) / 0.2 = 35Hz then (35Hz * 0.2) / 0.9 = 7.78
ft/sec. This defines the start ft/sec search point for the
actual flow velocity peak. Must be set greater than
value set for VF_NYQUIST_HIGH.

FLOW_VEL_SEARCH_LIMIT_HIGH Float

R/W

Define high end of velocity search range to use for
determining flow velocity. Defined by: Velocity_Max =
(FREQ_MIN * Sensor Spacing) /
VF_SEARCH_LIMIT_HIGH. Example: at 10ft/sec* (10
ft/sec*0.3) / 0.2 = 15Hz then (15Hz * 0.2) / 0.15 = 20
ft/sec. This defines the start ft/sec search point for the
actual flow velocity peak. Must be set less than value
for VF_NYQUIST_LOW.

FLOW_NYQUIST_INITIAL_VALUE Float

R/W

This parameter selects the k value (from k-w) where the
algorithm initially searches for the flow rate.

FLOW_DECIMATION

Unsigned
Long

R/W

Flow Decimation

FLOW_WINDOW_TYPE

Unsigned
Long

R/W

Algorithms always use Hanning window. Windows raw
data samples of NFFT size* then zero pads* then
computes FFT.

FLOW_DETREND

Unsigned
Long

R/W

Enable/disable detrend of time series data of NFFT size
before windowing and zero padding. 0 - Do not detrend
time series data* 1 - Detrend time series data.

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