Emerson Process Management 8732 Pv Urv, Upper Range Value, Pv Lrv, Lower Range Value, Example

Rosemount 8732

Reference Manual

00809-0100-4663, Rev BA January 2010

PV URV

(Upper Range Value)

Fast Keys 1, 3, 4

PV LRV

(Lower Range Value)

Fast Keys 1, 3, 5

The upper range value (URV), or analog output range, is preset to 30 ft/s at the factory. The units that appear will be the same as those selected under the units parameter.

The URV (20 mA point) can be set for both forward or reverse flow rate. Flow in the forward direction is represented by positive values and flow in the reverse direction is represented by negative values. The URV can be any value from –39.3 ft/s to +39.3 ft/s (-12 m/s to +12 m/s), as long as it is at least 1 ft/s (0.3 m/s) from the lower range value (4 mA point). The URV can be set to a value less than the lower range value. This will cause the transmitter analog output to operate in reverse, with the current increasing for lower (or more negative) flow rates.

NOTE

Line size, special units, and density must be selected prior to configuration of URV and LRV.

Set the lower range value (LRV), or analog output zero, to change the size of the range (or span) between the URV and LRV. Under normal circumstances, the LRV should be set to a value near the minimum expected flow rate to maximize resolution. The LRV must be between

–39.3 ft/s to +39.3 ft/s (-12 m/s to +12 m/s).

NOTE

Line size, special units, and density must be selected prior to configuration of URV and LRV.

Example

If the URV is greater than the LRV, the analog output will saturate at 3.9 mA when the flow rate falls below the selected 4 mA point.

The minimum allowable span between the URV and LRV is 1 ft/s (0.3 m/s). Do not set the LRV within 1 ft/s (0.3 m/s) of the 20 mA point. For example, if the URV is set to 15.67 ft/s (4.8 m/s) and if the desired URV is greater than the LRV, then the highest allowable analog zero setting would be 14.67 ft/s (4.5 m/s). If the desired URV is less than the LRV, then the lowest allowable LRV would be 16.67 ft/s (5.1 m/s).

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