Emerson Process Management 2051 manual Filtering, Low Cutoff, Rosemount, Reference Manual

Rosemount 2051

Reference Manual

00809-0200-4101, Rev AA July 2008

Solution

Table 3-5 lists the appropriate configuration settings.

Table 3-5. Analog Input Function Block Configuration for a Differential Pressure Transmitter.

Parameter		Configured Values
L_TYPE		Indirect Square Root
XD_SCALE		0 to 20 in.H2O
OUT_SCALE		0 to 800 gal/min.
Channel		1 - pressure
Out =	PV------------------------------------------------–XDSCALE0(OUTSCALE100 – OUTSCALE0) + OUTSCALE0
	XDSCALE100
OUT=	8inH2O – 0inH2O
	20inH-----------------------------------------------------2O– 0inH2O (800gal/min. - 0gal/min.) + 0gal/min. = 505.96gal/min.

Filtering	The filtering feature changes the response time of the device to smooth
	variations in output readings caused by rapid changes in input. Adjust the
	filter time constant (in seconds) using the PV_FTIME parameter. Set the filter
	time constant to zero to disable the filter feature.

Figure 3-3. Analog Input

PV_FTIME filtering Diagram.

Low Cutoff

OUT (mode in man)

OUT (mode in auto)

PV

63% of Change

FIELD_VAL

Time (seconds)

PV_FTIME

When the converted input value is below the limit specified by the LOW_CUT parameter, and the Low Cutoff I/O option (IO_OPTS) is enabled (True), a value of zero is used for the converted value (PV). This option is useful to eliminate false readings when the differential pressure measurement is close to zero, and it may also be useful with zero-based measurement devices such as flowmeters.

NOTE

Low Cutoff is the only I/O option supported by the AI block. Set the I/O option in Manual or Out of Service mode only.

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