mensor PCS 400, Руководство по эксплуатации

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CALIBRATION
The
PCS 400
automatically adjusts the pressure
reading for the effects of temperature and non-
linearity within the calibrated temperature range of
15-45
°
C. The process is referred to as dynamic
compensation because each reading is so adjusted
before it is output to the display or to a communi-
cation bus. Thus, a calibrated
PCS 400
operated
within its temperature band, and with proper zero
and span adjustments, will provide accurate pres-
sure measurements.
The
PCS 40
0 should have the span verified peri-
odically on each of its transducers to insure their
stability. Initially, the recommended period be-
tween calibrations is 180 days. This period may be
extended as confidence is gained in the span stabil-
ity.
CALIBRATION ENVIRONMENT
For maximum accuracy, the PCS 400 should be
allowed to warm up in the STANDBY mode for a
minimum of 45 minutes in an ambient tempera-
ture which is in the specified calibration range, and
stable. In addition the instrument should be at rest
on a stable platform which is free of excessive
vibration and shock.
PRESSURE STANDARD
Mensor recommends the use of appropriately ac-
curate primary pressure standards when calibrat-
ing this instrument. Such standards should be
sufficient so that when the techniques of the ISO
Guide to the expression of Uncertainty in Meas-
urement
(GUM) are applied, the instrument meets
its accuracy statements as required by ANSI/NCSL
Z540 , or other applicable standards.
CALIBRATION MEDIUM
The recommended calibration medium is dry ni-
trogen or clean dry instrument air. For low pres-
sure ranges (< 20 psi), head pressure differences
between the standard and the
PCS 400
can cause
errors. See ‘Head Pressure Correction’ in the Ap-
pendix .
CALIBRATION PROCEDURES
For convenience, the procedures for zero and span
adjustment for a gauge pressure instrument are
presented first followed by the procedures for an
absolute pressure instrument. Figure 6.1 (Gauge
Calibration Setup) and figure 6.2 (Absolute Cali-
bration Setup) illustrate typical setups for either
local or remote calibration. In the figures the addi-
tional equipment required for remote calibration
are shown as optional.
In both of the calibration setup illustrations the
“Pressure Standard” is normally a deadweight test
instrument, and the “volume controller” refers to a
hand operated variable-volume pressure vernier
device. A diaphragm type vacuum gauge is recom-
mended over the gauge tube type of vacuum sensor
for calibrating sub-atmospheric pressures. Where
a vacuum source is required a minimum capacity
of 21 liters per minute is recommended.
NOTES:
1. The recommended units for making
zero or span adjustments are psi. Other
engineering units might add a small
roundoff error.
2. When this instrument was calibrated
at the factory the zero and span correc-
tions were stored in memory. If the zero
or span values are changed at the front
panel, or over the remote bus, the new
values immediately displace the factory
values in memory. It is recommended
that a permanent record be maintained
of the ‘as received’ values, as well as the
values that result from each subsequent
zero and span update.
3. If the
PCS 400
uses more than one
pressure transducer in the MEASURE
mode, then the transducer to be cali-
brated must be selected as the “active”
transducer. Use the [LIMITS], [ACTIVE
XDUCER] functions from the keypad or
‘_PCS4 XDUCER digits’ command over
the GPIB to select the transducer that is
to be “active” for calibration. (digits) is
the number of the sensor to be active.
PCS 400
CALIBRATION
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