BAM 1020-9800 Manual Rev W.docx
Page 30
The mass density
“m”
(mg/cm
2
) of the reference membrane calculated during this automatic
process is compared to the known mass of the membrane; the
“ABS”
value. During factory
calibration, the actual mass of each individual span foil is determined and saved as the
ABS
value of the BAM-1020 in which it was installed. Each measurement of
m
must match the
ABS
value within ±5%. If not, the BAM 1020 records a
“D” alarm for that hour’s data.
Typically, the value of
m
is within a few mg/cm
2
of the expected value. The
ABS
value is
unique to each BAM 1020, and can be found on the calibration sheet. Most membrane
alarms are caused by a dirty membrane foil.
The stability measurements
𝐼
1
and
𝐼
1
′
may be compared to determine if the beta counts have
changed appreciably during the measurement cycle. Rapid changes in temperature, relative
humidity or other factors may lead to this.
4.3 Filter Tape Use
The BAM 1020 positions the filter spots very close to one another so as not to waste filter
tape. Once each day at midnight, the BAM 1020 will skip a spot (there will not be a spot
where one is expected to be). This is done to make it easier for the user to match the spot on
the take up spool with the hour and the day the spot was generated if this is necessary to be
done. Met One Instruments currently offers filter tape using part number 460180.
