Emerson Rosemount 2140, Справочное руководство, Страница: 11 / 144

1
Reference Manual
00809-0100-4140, Rev AA
Introduction
January 2017
Introduction
Section 1 Introduction
1.1 Models covered
The following point level detectors are covered by this manual:

Rosemount 2140 Level Detector – Vibrating Fork

Rosemount 2140:SIS Level Detector Vibrating Fork
Note
For detailed information about proof-testing the Rosemount 2140:SIS, refer to the
Rosemount 2140:SIS
Functional Safety Manual .
1.2 Point level detector overview
The Rosemount 2140 and Rosemount 2140:SIS are point level detectors, and are designed
to use the principle of a tuning fork. A piezo-electric crystal oscillates the forks at their
natural frequency, and changes to this frequency are continuously monitored by
electronics. The frequency of the vibrating fork sensor changes depending on the liquid
medium in which it is immersed. The denser the liquid, the lower the frequency.
When the level detector is used as a low level alarm, the liquid medium in the tank or pipe
drains down past the fork, causing a change of frequency that is detected by the electronics
and it indicates a dry condition.
When the level detector is used as a used as a high level alarm or for overfill detection
(
Figure 1-1 ), the liquid medium rises in the tank or pipe, making contact with the fork which
then causes the electronics to indicate a wet condition.
The wet and dry conditions can be transmitted digitally as a HART
®
signal or as a discrete
output using the analog output. See “Analog output type and operating modes” on
page 23 for details.
Figure 1-1. Typical Application