RUSKA 2413, 2417 & 2416
Users Manual
10-2
c.
The presence of an unrecognized pressure bias on the diaphragm at the time of
adjustment. If the top section of the transducer contains a liquid at the time of
adjustment, removal of the pinion access plug and insertion of the adjusting
screwdriver will create an abnormal pressure bias on the diaphragm; liquid
pressure heads are different than for normal operations. Allowance must be made
for the magnitude of the head when making the adjustment either by trial and
error or by adjusting the external heads to match the internal ones.
Bias pressures from other sources may be present and, unless they remain
constant throughout the measurement process, will affect the stability of the null
pressure adjustment.
The accuracy to which the adjustment must be made will depend upon:
1.
The skill of the operator in neutralizing, or otherwise accounting for, the abnormal
pressure bias on the diaphragm as described in C, above.
2.
The number of potentiometer dial units that span the change in null indication from
zero to full working pressure. This information is obtained from the calibration
report. The curve representing the change in potentiometer dial counts versus
operating pressure level indicates the total number of counts that must be available to
the operator for completion of his process. The zero adjustment potentiometer must
be offset at the initial adjustment to accommodate this range of operation.