2 The Rosemount 3101, 3102, and 3105
The Rosemount 3101, 3102, and 3105 are 4–20 mA loop-powered level
transmitters designed for continuous liquid level measurements in tanks or
open flow channels.
They can be connected directly to a plant control system, or used with a
Rosemount 3490 Series Control Unit for programmable control
functionality. The Rosemount 3105 may be mounted in a hazardous area if
powered from a protected power supply.
2.1 Theory of operation
The transmitter is designed to be mounted above a liquid and uses
ultrasonic pulses to continuously measure the distance to the liquid surface.
The microprocessor-controlled electronics calculates distance to the liquid
level from the time delay between the transmitting and receiving of signals.
When programmed with the bottom reference of the application – usually
the bottom of a tank (Figure 2-1) – the transmitter calculates the liquid
depth (level) and outputs the level as a 4–20 mA signal (and a digital HART
®
signal on the 3102 and 3105).
The Rosemount 3101 measures level only. The Rosemount 3102 and 3105
can calculate distance-to-surface, contents (volume), or open channel flow,
and then output the result as a 4–20 mA signal and a digital HART signal.
An LCD screen inside the enclosure displays the selected measurement.
Programming is achieved using integral buttons inside the enclosure (all
models) or by remote communication using HART (on the 3102 and 3105
only).
August 2019 Quick Start Guide
Quick Start Guide 5
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