Adjustments; Control Action; Level Adjustment (Controllers Only); Zero Adjustment (Transmitters Only) - Fisher 2500 Series Instruction Manual

5. Increase the process variable until the OUTPUT
gauge changes to full supply pressure for direct or 0
psig (0 bar) for reverse action. The process variable
should be at the desired high trip value.
6. Decrease the process variable until the OUTPUT
gauge changes to 0 psig for direct or full supply pres-
sure for reverse action. The process variable should
be at the desired low trip value.
7. If all prestartup checks are satisfactory, proceed to
the Startup section. If performance is unsatisfactory,
proceed to the Calibration section.

Adjustments

This section explains controller/transmitter action and
adjustments. Figure 12 shows adjustment locations.

Control Action

The following is a definition of control action.
Direct Action—Increasing fluid level, interface
level, or density, increases the output signal.
Reverse Action—Increasing fluid level, interface
level, or density, decreases the output signal. Control-
ler/transmitters factory-set for reverse-acting have the
suffix letter R added to their type number.
The control action is determined by the cage head
mounting position and by the Bourdon tube-flapper
arrangement in the controller/transmitter. Refer to fig-
ure 4 for mounting positions and to figure 17 for Bour-
don tube-flapper arrangements. To change the action,
refer to the changing action procedure in the Mainte-
nance section.

Level Adjustment (Controllers Only)

To make a level adjustment, open the controller cover,
loosen the knurled adjustment screw, and rotate the
adjustment lever around the RAISE LEVEL dial. To
raise the fluid or interface level, or increase density,
rotate this knob in the direction of the arrows. To lower
the level or decrease density, rotate the knob in the
opposite direction. This procedure is the same for ei-
ther direct or reverse action. Tighten the knurled
screw.
The raise level dial does not reflect actu-
al fluid level in the tank or fluid level
position on the displacer.
Note

Zero Adjustment (Transmitters Only)

To make a zero adjustment, open the transmitter cov-
er, loosen the adjustment screw and rotate the adjust-
ment lever around the ZERO ADJUSTMENT dial. This
adjustment sets the output pressure to correspond to
a specific level on the displacer. Tighten the knurled
screw.
Proportional Band Adjustment (Except
Transmitters and 2503 Series Controllers)
The proportional band adjustment varies the amount
of process variable change required to obtain a full
output pressure change. To perform this adjustment,
open the controller cover and turn the PROPORTION-
AL BAND adjustment (see figure 12). Refer to the
prestartup check procedures to determine the proper
setting.
Specific Gravity Adjustment (Transmitters
Only)
This adjustment also varies the amount of process
variable change required to obtain a full output pres-
sure change. To perform this adjustment, open the
transmitter cover and turn the SPECIFIC GRAVITY
adjustment (see figure 12). Refer to the prestartup
check procedures to determine the proper setting.

Calibration

Precalibration Requirements

The controller/transmitter can be calibrated in the field,
mounted on the vessel containing the process fluid. It
may also be done in the shop, but other means of ob-
taining a displacement force change must be provided.
There are wet and dry methods of adapting the cali-
brating procedure.

Wet Calibration

Remove the entire controller/transmitter and sensor
assembly from the vessel. For caged sensors, pour
the fluid into the cage. For cageless sensors, suspend
the displacer to an appropriate depth in a fluid having
a specific gravity equal to that of the process fluid.
If necessary, you may use water for wet calibration in
the shop. You must compensate for the difference be-
tween the specific gravities of water and the process
fluid, however. As an example, assume the process
fluid has a specific gravity of 0.7. The specific gravity
of water is 1.0. To simulate a process level of 50 per-
cent of the input span, would require a water level of
35 percent (0.7/1.0 x 50 percent = 35 percent).
Type 2500
15