Rosemount 1151GP - Page 47

Reference Manual
00809-0100-4360, Rev BA
August 2008
3-11
Rosemount 1151
Setting Output Type
When the square root output option is active the Rosemount 1151 analog
output is proportional to flow. To avoid the extremely high gain that results as
the input approaches zero, the Rosemount 1151 automatically switches to a
linear output in order to ensure a more stable output near zero. Figure 3-6
illustrates this transition point.
The transition from linear to square root is not adjustable. It occurs at 0.8% of
ranged pressure input or 9.0% of full-scale flow output in transmitters with
Revision 5.2. software. In earlier software, the transition point occurred at
4.0% of ranged pressure input, or 20% of full scale flow output.
The transition from linear to square root output is smooth, with no step change
or discontinuity in output.
Figure 3-6. Square Root Output
Transition Point.
HART Comm. Fast Key Sequence 1, 3, 5
Full Scale
Flow (%)
Square Root
Curve
Transition Point
Linear Section of Curve
Full Scale Pressure (%)
0.8%
Slope = 42
Slope = 1
Linear
Transition
Detail
Full Scale Pressure (%)
Square
Root
Curve
Linear
Section
of Curve
Transition
Point
Full Scale
Flow (%)
Full Scale
Output (mA dc)
Full Scale Output
(mA dc)