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Servomex 2500 Quick Start Manual
24 2500 Series - Configuration and Operation 02500/003E/0
4 CALIBRATION
4.1 Introduction to calibration
The 2500 series is supplied by Servomex with an accurate factory calibration for the
measurement required as specified on the customer's order. This calibration contains a
zero constant, a span constant and a linearising function, which are stored in the 2500
and cannot be erased or overwritten by the user.
The user is able to make adjustments to span and zero, however, in order to suit his
own site conditions and calibration standards. User adjustments, using the calibration
routines in this section, modify the factory values only when the appropriate
FUNCTIONS have been ‘unlocked’ (set to ‘USER’) as described in Section 3.7.
Factory values are restored whenever the FUNCTIONS are set back to ‘DEFAULT’.
Two types of calibration operation are available:
i) True CALIBRATIONS, where the zero and span of the 2500 are adjusted.
ii) Sample CHECKS, where the 2500 is tested with zero and span, but no
adjustments are made.
In either case, results are logged in the appropriate Calibration History log. Either type
of calibration can be performed MANUALLY or AUTOMATICALLY.
NOTE
•
It is likely that SPAN adjustments will be required less often than ZERO
adjustments on the 2500 series, due to its inherent span stability.
•
At this stage, if true CALIBRATIONS are to be required, unlock the necessary
FUNCTIONS before proceeding.
•
All Calibration Samples must have stable and accurately known concentrations of
the measured component in a background representative of the actual process
stream, and they must be supplied to the 2500 at typical process temperature,
pressure and flow rate.
4.2 Setting low and high calibration tolerances
The Zero and Span Tolerances are the limits, set by the user, on the permissible range
of adjustments during manual and auto calibration routines. These warn of incorrect
samples or excessive drift.
If a tolerance is about to be exceeded during a manual calibration, a warning is given.
This can be ignored if necessary.
If a tolerance is about to be exceeded during an auto calibration, the auto calibration
will fail and the Fault alarm will be signalled.
The maximum permissible tolerance is 10% fsd in either case.