Reference Manual
00809-0100-4690, Rev FC
June 2011
3-9
Rosemount 2088 and 2090
Rerange The Range Values command sets each of the lower and upper range analog
values (4 and 20 mA points and 1 and 5 Vdc points) to a pressure. The lower
range point represents 0% of range and the upper range limit represents
100% of range. Setting the range values to the limits of expected readings
maximizes transmitter performance; the transmitter is most accurate when
operated within the expected pressure ranges for your application. In practice,
you may reset the transmitter range values as often as necessary to reflect
changing process conditions.
NOTE
Transmitters are shipped from Emerson Process Management fully calibrated
per request or by the factory default of full scale (zero to upper range limit).
NOTE
Regardless of the range points, the Rosemount 2088/2090 will measure and
report all readings within the digital limits of the sensor. For example, if the 4
and 20 mA points are set to 0 and 10 inH
2
0, and the transmitter detects a
pressure of 25 inH
2
0, it digitally outputs the 25 inH
2
0 reading and a 250
percent of span reading.
You may use one of three methods to rerange the transmitter. Each method is
unique; examine all three closely before deciding which method to use.
Method 1: Rerange with a Field Communicator or AMS Device Manager
This is the easiest and most popular way to rerange the transmitter. This
method changes the values of the analog 4 and 20 mA points (1 and 5 Vdc
points) independently without a pressure input. This means that when you
change either the 4 or 20 mA setting, you also change the span.
To rerange using only the communicator enter the fast-key sequence above,
select 1 Keypad input, and follow the on-line instructions or enter the values
directly from the HOME screen.
Field Communicator
Method 2: Rerange Using the Communicator and a Pressure Source or
Process Pressure
Reranging using the communicator and a pressure source or process
pressure is a way of reranging the transmitter when specific 4 and 20 mA
points (1 and 5 Vdc points) are not known.
NOTE
The span is maintained when the 4 mA point (1 Vdc point) is set. The span
changes when the 20 mA point (5 Vdc point) is set. If the lower range point is
set to a value that causes the upper range point to exceed the sensor limit,
the upper range point is automatically set to the sensor limit, and the span is
adjusted accordingly.
To rerange using the communicator and a pressure source or process
pressure, enter the fast-key sequence above, select 2 Apply values, and
follow the on-line instructions.
4-20 mA Fast Keys
1, 3, 3
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