Reference Manual
00809-0100-4360, Rev BA
August 2008
4-17
Rosemount 1151
Linearity Adjustment In addition to the span and zero adjustments, a linearity adjustment screw
(marked LIN) is located on the solder side of the amplifier board. See Figure
4-11. This is a factory calibration adjusted for optimum performance over the
calibrated range of the instrument and normally is not readjusted in the field.
The user may, however, maximize linearity over a particular range using the
following procedure:
1. Apply mid-range pressure and note the error between the theoretical and
actual output signal.
2. Apply full-scale pressure. Multiply the error noted in Step 1 by six and
then that product by the Range Down Factor, which is calculated as
shown below:
Add this result to the full-scale output (for negative errors), or subtract the
result from the full-scale output (for positive errors) by turning the linearity
adjustment screw.
Example: At 4 to 1 Range Down Factor, the mid-scale point is low by 0.05
mA. Therefore, turn the linearity adjustment screw until full-scale output
increases by (0.05 mA 6 4) = 1.2 mA.
3. Readjust the zero and span.
Figure 4-11. Damping and
Linearity Adjustment Screws.
Damping Adjustment The amplifier boards for output options E and G are designed to permit
damping of rapid pulsations in the pressure source through adjustment of the
damping screw shown in Figure 4-11 on page -17. The adjustment is marked
DAMP on the solder side of the amplifier board.
The settings available provide time constant values between 0.2 and 1.66
seconds. The instrument is calibrated and shipped with this control set at the
counterclockwise stop (0.2 second time constant). It is recommended that the
shortest possible time constant setting be selected. Since the transmitter
calibration is not influenced by the time constant setting, the damping may be
adjusted with the transmitter connected to the process. Turn the damping
control clockwise until the desired damping is obtained.
Range Down Factor
Maximum Allowable Span
Calibrated Span
---------------------------------------------------------------------=
Access to linearity and damping adjustments is gained by
removing cover on circuit board side.
Location of linearity adjustment screws may vary slightly between
output codes.
Damping
Adjustment
Screw
Linearity
Adjustment
Screw
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