User Guide

MAINTENANCE AND CALIBRATION - DIFFERENTIAL PRESSURE RECORDER
CALIBRATION CHECK
A. Differential Pressure Pen
Normally, all that is required to adjust the instrument calibration to factory settings is to perform the following procedure:
1. Verify that the instrument is positioned level and is securely mounted.
2. Connect the high pressure housing into the set-up shown in figure 6.
3. Vent the DPU low pressure side to atmosphere by removing one vent plug from the low pressure housing.
4. Place a recording chart onto the chart plate of the recorder, lock the chart in position using the hub clip.
NOTE: There should be enough pen pressure on the chart to produce a continuous line.
5. Set pen precisely at zero indication using pen zero adjust screw (see fig 3).
6. Apply 100% differential pressure and observe position of the pen; the pen should be at 100% indicating position
on the chart.
7. Apply 50% pressure and observe position of the pen; the pen should be at the 50% indicating position on the
chart.
8. If the pen does not accurately indicate pressure being applied, further adjustments are necessary. Perform
calibration procedure outlined in the section below.
CALIBRATION OF DIFFERENTIAL PRESSURE PEN
To calibrate the differential pressure pen and associated linkage, proceed as follows:
1. Verify that chart plate is on the same plane and is flush with the chart hub flange. The chart must be flat with the
hub locked.
2. With a recorder chart locked into place, move the differential pressure pen from zero to full span and back to make
certain that the pen travels along the time line of the chart. If adjustment is required, loosen the two pen clamping
screws and adjust pen arm length until the differential pressure pen follows the time line. Tighten the pen clamping
screws.
NOTE: Linkage may be disconnected to perform this operation.
3. Verify that pens and pen arms are connected correctly and that pens don't interfere with one another.
4. Disconnect the horizontal adjustable link from the drive arm and static pressure drive link from its take-off arm/coil
lever. Adjust the static pressure pen so that the pens are approx. 4mm apart by adjusting the static pressure pen
length. If adjustment is required, loosen the two pen clamping screws and adjust static pressure pen arm length
until it is sufficiently clear of the differential pressure pen arm and the two pens do not interfere with one another
across the full span of the chart. Only adjust the static pressure pen as necessary, do not alter the differential
pressure pen once it has been adjusted to the time line.
5. Make sure there is enough pen pressure on the chart to produce a continuous line. If adjustment is required,
adjust the pen friction screw on the pen plate as necessary.
6. Verify that pen lifter does not interfere with the rotation of the chart paper or recorder pens across the whole chart
range. If adjustment is required simply bend pen lifter to required position using a suitable pair of pliers.
7. Unlock the chart hub and revolve chart manually to verify chart clips do not interfere with chart paper. If
adjustment is required, gently ease the clip(s) upwards to provide a larger gap for the chart.
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