Rosemount 1151GP - Reranging with a Communicator and a Reference Pressure

Reference Manual
00809-0100-4360, Rev BA
August 2008
3-9
Rosemount 1151
Reranging with a Communicator and a Reference Pressure
Reranging with a pressure input source and the communicator allows you to
maintain the same analog span.
For instance, if the transmitter is ranged so that:
4 mA = 0 inH
2
O, and
20 mA = 100 inH
2
O,
and you then change the 4 mA setting to 50 inH
2
O using the communicator (or
buttons) and a pressure input, the new settings are:
4 mA = 50 inH
2
O
20 mA = 150 inH
2
O
The 100 inH
2
O span is maintained.
To rerange with a reference pressure, apply the desired pressure input to
represent the 4 or 20 mA point. Allow the variable reading to stabilize for
approximately ten seconds. Press either the 4 mA or 20 mA to make this
pressure value either point.
It is also important to note that when using a pressure source, the 4 and 20
mA setpoints are based on the transmitter’s interpretation of the pressure
input provided. It is possible that when a plant standard is input, the
transmitter reads it as a slightly different value. Although the 4 and 20 mA
setpoints will operate properly within these applied settings, the transmitter’s
digital output in engineering units may indicate a slightly different value.
The sensor trim function under “Digital Trim” can be used to match the
transmitter’s reading in engineering units to your plant standard, thereby
eliminating any discrepancy.
NOTE
Reranging only the 4 mA or the 20 mA with a pressure input will maintain the
initial span width.
NOTE
Do not rerange the transmitter such that the 4 and 20 mA range points—
upper range value (URV) and lower range value (LRV)—are outside the high
and low digital sensor trim values. To optimize performance, the digital trim
span should be equal to or slightly greater than the 4–20 mA span.
HART Comm. Fast Key Sequence 1, 2, 3, 1, 2