Emerson Bristol 2808 Series, Instruction Manual

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2808B Calibration / 3-11
3.8.1 Zero Suppression Example (see Figure 3-3 & Table 3-B)
The full water tower of Figure 3-3, produces 53.5 psi of pressure due to the 125 foot head,
i.e 10.7 psi plus 42.8 psi. To determine the Coarse Span Rotary Switch (SW1) setting, divide
the pressure produced by the 25 feet of water in the tank by the Transmitter’s range; in this
case 50 psi, i.e., 10.7/50 = 21.4%. Therefore, the SW1 should be set to position 8 (18.5% -
23%).
To determine the zero suppression necessary for this example, divide the pressure produced
by 100 feet of water (height of tower to bottom of tank) by the Transmitter’s range; in this
case 50 psi, i.e., 42.8/50 = 85.6%. With the Coarse Span Rotary Switch SW1 set to its SW1-8
position, set the value of the Coarse Zero Switch (S1) to either -80% (00001100) or -90%
(00001010), or to a binary value between the two e.g., 00001011 (-85%).
Use Fine Adjustment Screw A2 to set 1.000V (4.00mA) @ 42.8 psi and use Fine Adjustment
Screw A1 to set 5.000V (20.00mA) @ 53.5 psi.
Note: When Zero Suppression is used, the maximum applied pressure may be up
to 125% of the URL.
3.9 SELECTABLE DAMPING
The damping feature provides compensation for applications with severe pressure pulsation
that will cause the DC output of the Transmitter to seem unstable. Controlling the response
time of the Transmitter output can minimize this condition. Do not use damping when the
application requires dynamic pressure measurement.
Jumper JP9 can be set to apply damping to the output. With jumper JP9 in place, the
damping is on. If the jumper does not connect the two pins together, the damping is off.