Table of Contents
Advertisement
1.2.4.2
molbloc-S
The flow range and operating pressure associated with molbloc-S operation
depend on the molbloc used and its calibration options (see Section 1.2.4.2.2)
Measurement Update
Rate
Range
Resolution
Linearity
Repeatability
1
Precision
2
Predicted Stability
(1 year)
Measurement
3
Uncertainty
With SP molbloc-S
calibration
Measurement
3
Uncertainty
With LP molbloc-S
calibration
1
Precision: Combined linearity, hysteresis, repeatability.
2.
Stability: Maximum change in zero and span over specified time period for typical molbox RFM
and molbloc used under typical conditions. As stability can only be predicted, stability for a
specific molbloc and molbox RFM should be established from experience.
3.
Measurement uncertainty (accuracy): Maximum deviation of the molbox RFM flow indication
from the true value of the flow through the molbloc including precision, stability and DHI
calibration standard measurement uncertainty.
1.2.4.2.1
molbloc-S RANGES
molbloc-S flow ranges are defined by the molbloc's Pressure to Flow Conversion
Ratio, K
, the absolute pressure that can be delivered upstream of molbloc-S, the
F
downstream pressure and the acceptable back pressure ratio (see Section
3.1.2).
K
is expressed in units of sccm/kPa and defines the relationship
F
between mass flow and the absolute upstream pressure delivered to the
molbloc-S. molbloc-S sizes are defined by the nominal K
nozzle, using scientific notation, for example a 1E3 molbloc-S has a K
sccm/kPa. To differentiate from molbloc-L size designations, this molbloc size is
designated 1E3-S.
The molbox RFM pressure range, the molbloc-S calibration type (see Section
1.2.4.2.2) and the back pressure ratio (BPR) requirements (see Section 3.1.2)
limit the pressures, and flows, over which a molbloc-S can be used within known
measurement uncertainty limits. In practice, the usable range of a molbloc-S in a
given application also may depend on the available gas supply pressure, the presence
and flow capacity of a vacuum pump downstream or the allowable back pressure
on an upstream DUT.
The flow ranges for each molbloc-S size at various typical operating pressures
are summarized in Table 4 and the BPR limits are in Table 5.
1 second
Depends on molbloc-S pressure dependent calibration type
(see Section 1.2.4.2.2)
0.01 % of FS
± 0.25 % of reading
± 0.10 % of reading
± 0.30 % of reading
± 0.2 % of reading
± 0.5 % of reading from 50 to 500 kPa
±
0.5
%
of
reading
± 0.5 % of 50 kPa flow from 20 to 50 kPa
Page 9
© 1998-2007 DH Instruments, a Fluke Company
1. INTRODUCTION
from
50
to
200
kPa
of the molbloc-S
F
1 000
F
Advertisement
Table of Contents
