2-5
EN
Rerange
The
Range Values
command sets the 4 and 20 mA points (lower and upper range
values). 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.
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.
NOTE
Regardless of the range points, the Model PX2088 Smart 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
O, and the transmitter detects a pressure of 25 inH2O,
it digitally outputs the 25 in H
2
O reading and a 250% percent of span reading.
However, there may be up to ±5.0%
error associated with output outside of the range
points.
Method 1: Rerange Using the Communicator
Reranging using only the communicator is the easiest and most popular way to
rerange the transmitter. This method changes the values of the analog 4 and 20
mA points independently without a pressure input.
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.
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 are not known.
This method changes the values of the analog 4 and 20 mA points. When you set
the 4 mA point the span is maintained; when you set the 20 mA point the span
changes.
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.
Method 3: Rerange Using the Local Zero and Span Buttons
and a Pressure Source or Process Pressure
Reranging using the local zero and span adjustments and a pressure source is a
way of reranging the transmitter when specific 4 and 20 mA points are not known
or a communicator is not available. When you set the 4 mA point the span is
maintained; when you set the 20 mA point the span changes.
To rerange using the zero and span adjustments, refer to “Rerange Procedure” on
page 4-13.
HART Fast Keys
1, 3, 3
4690.bk : 4690.s2 Page 5 Tuesday, May 26, 1998 5:28 PM
