IMKO Trime-GW, Руководство по эксплуатации

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4.2 Basis calibration after replacing system components
4.2.1 General notes regarding basis calibration
System components directly involved in the measuring process (probe, probe lead, transducer) are
aligned with each another by means of the basis calibration. Manufacturing tolerances influencing the
measurement reading are compensated for.
New instruments are supplied with the basis calibra-
tion already performed. The process must be repeated if one of the system components men-
tioned above has been repaired or replaced. Calibration at the factory is not possible unless
the unit has been sent in with all components stated above.
Basis calibration involves taking two reference measurements in media of a known value ("reference
value") correcting any divergence of the unit from these reference values where necessary. TRI-
ME
®
-GW calculates the correction values required for this ("offset" and "slope") itself and stored in
non-volatile form in the instrument, i.e. they remain intact even when the power supply is switched off.
Air and dry glass beads are used as reference media.
The procedure is carried out using the GW basis-calibration set available as an optional extra and
comprising:

dry glass beads,

RS232 cable

Software WinCal
4.2.2 Reference values of the calibration media used for the basis calibration
The reference values listed below apply for the appropriate calibration media.
Table 10
Reference value
before material calibration
and offset correction
(pseudo-transit time)
Permissible tolerance for test
measurements
Calibration medi-
um
Air -11.0 %

0.5%
Dry glass beads +12.7 %

0.2%
4.2.3 Preparatory measures
The “dry glass beads” and probe required for the basis calibration must themselves be around room
temperature (18..24°C).
4.2.4 The procedure using the configuration plug “TRIME
®
-GW basis calibration”
1. To set the first reference value “air” the probe must be positioned in such a way that within a field
of at least 15 cm only air surrounds the probe rods.
Note: It is by no means sufficient to place the probe on a table or something similar. The probe
can either be laid on the table so that the probe rods are fully overhanging the edge and the first
2..3 cm of the probe body are overhanging it as well. Alternatively, hold the it your hand at the
very rear (!) of the probe body to ensure that the hand does not invade the field of measurement
which also registers the front 3..4 cm of the probe body.
2. If the measurement was erroneous, the value “E.EE” is displayed instead of the reference value
"39.0". If this occurs, basis calibration must be repeated from step 1.
Note: If the basis calibration procedure is not continued to take the second reference measure-
ment (“dry glass beads”) once the first reference measurement has been taken, only an offset cor-
rection has been performed, the slope remains unaltered. A “single-point basis calibration” such
as this can be used as a stopgap if no “dry glass beads” are available. A “two-point basis calibra-
tion” should be carried out later on though. Please also refer to the notes at the end of the section
on performing the basis calibration.
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