Range Jumper; Action; Removing The Electronic Circuit Board; Product Change - Emerson Fisher 846 Instruction Manual

Instruction Manual
Form 5739
February 2002
NOTE:
1
RPR JUMPER ONLY ON UNITS WITH REMOTE
PRESSURE READING (RPR) OPTION
A6652/IL
Figure 6-5. Circuit Board Jumper Positions
When operating Type 846 and Model
3311 transducers in series, only one
unit may be configured for Remote
Pressure Reading. Activating the RPR
feature in two units will result in an
unusable RPR signal.

Range Jumper

The range jumper is positioned according to the
calibration specified. All full span calibrations and
some split range calibrations can be accomplished
with the range jumper in the High Range position.
Some split range calibrations require the jumper to
be in the Low Range position. For more information
about the range jumper, refer to Standard
Performance: Split Range Input, Direct Action in
Section 4.

Action

For direct action units, output changes directly with a
corresponding change in input. For example, as the
input increases from 4 to 20 mA the output
increases from 0.2 to 1.0 bar (3 to 15 psi). Direct
action circuit boards are green in color.
RPR OFF
LOW
RANGE
RPR ON
1
Note
For reverse action units, output changes inversely
with a change in input. For example, as the input
increases from 4 to 20 mA the output decreases
from 1.0 to 0.2 bar (15 to 3 psi). Reverse action
HIGH
circuit boards are red in color.
RANGE
Upon loss of input current, or if input current
decreases below 3.3 $0.3 mA, the output of the
direct action unit decreases to less than 0.1 bar (1
psi). In the same situation, the output of the reverse
action unit increases to near supply pressure.
1

Removing the Electronic Circuit Board

The electronic circuit board is connected to the
module final assembly by five mounting screws. The
circuit board must be removed to inspect the
pressure sensor located beneath it. To remove the
circuit board, remove the five mounting screws and
pull upward on the plastic board standoff
(black=multirange; white=standard).
Standard electronic assembly
handling procedures apply. Do not
attempt to remove the circuit board by
pulling on the components. Doing so
could weaken the connections and
disable the electronics.
Be careful when handling the pressure sensor
located beneath the circuit board. The pressure
sensor lead frame is bent to allow the pressure
sensor to fit properly in the sensor cavity of the
module final assembly, and to maintain flush contact
with the pressure sensor manifold.
Three O-rings accompany the pressure sensor. Two
O-rings of the same size are located on each side of
the pressure sensor. A third, smaller O-ring is
positioned in the beveled O-ring gland of the module
sub-assembly. Table 6-1 shows the O-ring sizes.
The pressure sensor may be gently bent away from
the pressure sensor manifold to access the sensor
O-ring and confirm that the pressure ports are clear.

Product Change

Previous electronic circuit boards have the two
sensor O-rings positioned on the shoulders of the
sensor. They also have a sensor seal washer that is
positioned in the bottom of the pressure sensor
cavity of the module subassembly. Both the
previous and the current designs are compatible
Maintenance
CAUTION
6–5