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4
Calibration
This chapter describes the procedure for calibrating your
instrument. If you have questions or problems regarding the
calibration procedure, please see Troubleshooting and Service.
Calibration procedure
Aside from requiring manual sample introduction, calibration of the
3250 is automatic. Following the procedure suggested below, you
simply select CALIB and initiate freezing-point tests on each of two
calibration standards required for the selected range.
The calibration standards required are:
• Low range: 100 and 1500 mOsm/kg H
O
• High range: 1500 and 3000 mOsm/kg H
O
The 3250 also offers an optional Zero calibration (0 mOsm/Kg HO) in
the low range only (see 17. Zero Calibration)
Internally, the 3250 accomplishes calibration in two steps for each
range. First, it records the raw means of the results of freezing point
tests on standards at each of the two calibration levels. Then it
performs the necessary conversion calculations and calibrates the
display. Each range is independently calibrated.
Check the calibration frequently, as recommended in Chapter 2, but do
not recalibrate when the calibration is satisfactory. It has been shown
that unnecessary recalibration will introduce inaccuracy. The calibration
of a freezing point osmometer in good condition and properly
operated will not shift or drift.
Both the High and Low ranges were initially calibrated at the factory.
However, each time the buzz point is changed, the calibration should
be checked and recalibrated if necessary. Also, anytime the sample or
block probe bin numbers are changed, recalibration will be required.
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