Incorrect Results - Micromeritics 1305 Operator's Manual

Model 1305 Multivolume Pycnometer
Purging is important to remove all air following opening and reclosing of the sam-
ple chamber. Air, especially moist air, behaves differently than helium or dry ni-
trogen and will cause the sample results to vary.
Zeroing must be done with care and accomplished as shortly before charging
with gas pressure as feasible. There is some difference between +0.000 and
-0.000; one or the other should be used consistently where absolutely best results
are sought.
Heat and moisture from the hands can cause significant effects. Use gloves or a
cloth when handling the sample cap and samples to help minimize these effects.
Using charging pressures, P
small but systematic variations in results due to the small amount of unavoidable
non-linearity in the pressure transducer.

Incorrect Results

Consistent, but incorrect measured volumes may be due to one or more of the fol-
lowing causes.
The >5/<5 valve or the >35/<35 valves are in the wrong position for the range in
use, or an incorrect sample chamber insert is being used. Refer to Chapter 3 for
information on valve positions and inserts.
Operation outside the 67-77 °F range on the 5-cm
recalibration at the new temperature. Refer to Calibrating the Analyzer in Chap-
ter 3.
The calibration may be invalid due to disassembly of tubing, alteration of sample
cups, exchange of sample cups or sample chamber inserts, or not using sample
cups when the instrument calibration was made with them in place. A sample
chamber cap which has changed in its seating will alter the calibration. Particles
on the sample chamber floor can cause the sample chamber inserts to protrude
and strike the cap, altering the seating, and causing errors. Refer to Calibrating
the Analyzer in Chapter 3 for instructions on checking and correcting the calibra-
tion.
Review carefully the computation of sample results and calibra tion constants to
ensure that errors are not being made. Confirm the correctness of calibration vol-
ume standards through measurements or other independent tests.
Use of charging pressure, P
calibration to compensate for any slight nonlinearity of the pressure transducer.
Jun 99
outside the 19.500 ±0.200 psig range will cause
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3
differing from the 19.500 ±0.200 psig will require re-
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Incorrect Results
full-scale range may require
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