Emerson Rosemount 3051, Справочное руководство, Страница: 62 / 222

52
Reference Manual
00809-0100-4001, Rev JA
Section 3: Configuration
November 2012
Configuration
3.9 Basic setup
3.9.1 Set process variable units
The PV Unit command sets the process variable units to allow you to monitor your process using
the appropriate units of measure.
Field communicator
Enter the fast key sequence “Set Process Variable Units.” Select from the following engineering
units:
AMS device manager
Right click on the device and select Configure from the menu. In the Basic Setup tab, select Unit
from the drop down menu to select units.
3.9.2 Set output (Transfer function)
The 3051 has two output settings: Linear and Square Root. Activate the square root output
option to make analog output proportional to flow. As input approaches zero, the 3051
automatically switches to linear output in order to ensure a more smooth, stable output near
zero (see
Figure 3-10 ).
For 4-20 mA HART output, the slope of the curve is unity (y = x) from 0 to 0.6 percent of the
ranged pressure input. This allows accurate calibration near zero. Greater slopes would cause
large changes in output (for small changes at input). From 0.6 percent to 0.8 percent, curve
slope equals 42 (y = 42x) to achieve continuous transition from linear to square root at the
transition point.
Traditional 4-20 mA Fast Keys
1, 3, 2
Traditional 1-5 Vdc Fast Keys
1, 3, 2
Device Dashboard Fast Keys
2, 2, 1, 1

inH
2
O

bar

torr

inHg

mbar

atm

ftH
2
O

g/cm
2

inH
2
O at 4 °C

mmH
2
O

kg/cm
2

mmH
2
O at 4 °C

mmHg

Pa

psi

kPa