Introduction; Scope Of Manual; Description; Specifications - Emerson Fisher 846 Instruction Manual

Type 846 and Model 3311
Section 1

Introduction

Scope of Manual

This instruction manual provides installation,
operating, calibration, maintenance, and parts
ordering information for the Type 846 and Model
3311 current-to-pressure transducers. Refer to
separate manuals for instructions covering
equipment used with the transducers.
Only personnel qualified through training or
experience should install, operate, or maintain these
transducers. If there are any questions concerning
the instructions in this manual, contact your Fisher
sales office or sales representative before
proceeding.
CAUTION
The products described in this
document are NOT designed for
nuclear-qualified applications. Using
non-nuclear qualified products in
applications that require
nuclear-qualified hardware or
products may cause inaccurate
readings.

Description

The Type 846 or Model 3311 current-to-pressure
transducer, shown in figure 1-1, accepts an electrical
input signal and produces a proportional pneumatic
output. Typically, 4 to 20 mA is converted to 0.2 to
1.0 bar (3 to 15 psi). Models are available in direct or
reverse action and field-selectable full or split range
inputs. See Section 3 Calibration for more
information on input/output combinations.
The most common application of the transducer is to
receive an electrical signal from a controller and
produce a pneumatic output for operating a control
valve actuator or positioner. The Type 846 and
Model 3311 may also be used to transduce a signal
for a pneumatic receiving instrument.
The Type 846 and Model 3311 are electronic I/P
transducers. They have a single electronic circuit
board, as shown in figure 1-2. The circuit contains a
solid-state pressure sensor that monitors output
pressure and is part of an electronic feedback
1–2
Figure 1-1. Type 846 and Model 3311 Current-to-Pressure
Transducer
network. The self-correcting ability provided by the
sensor/circuit combination allows the transducer to
produce a very stable and responsive output signal.
All active mechanical and electrical components of
the Type 846 and Model 3311 are incorporated into
a single, field-replaceable module called the module
final assembly, shown in figure 1-2. The module final
assembly contains the electronic circuit board,
pilot/actuator assembly, and booster stage. The
module final assembly is easily removed by
unscrewing the module cover. Its design minimizes
parts and reduces the time required for repair and
troubleshooting.
The terminal compartment and module compartment
are separated by a sealed compartment wall. This
multi-compartment housing also protects the
electronics from contaminants and moisture in the
supply air.

Specifications

Specifications for the Type 846 and Model 3311
transducer are listed in table 1-1.
Instruction Manual
Form 5739
February 2002