4
Calibration
This chapter describes the procedure for calibrating your
instrument. If you have questions or problems regarding the cal-
ibration procedure, please consult Chapter 5 —
Troubleshooting & Service.
Calibration procedure
Aside from requiring manual sample introduction, calibration of
the 4250 is automatic. Following the procedure suggested
below, you simply select CALIB and initiate six freezing-point
tests on each of two calibration standards, -422 m°H (-408
m°C) and -621 m°H (-600 m°C), as prompted by the display.
NOTE If calibration information has been lost or bin numbers
have been changed, the results may not match the nomi-
nal value.
The calibration procedure follows:
1. At “Cryoscope Ready” (or the date and time standby dis-
play), press CALIB. The CALIB soft key will light and the
display will quickly change to “Calibration”, then prompt
you for the first calibration standard.
If the sample probe is replaced, the sample probe bin # must
be determined and set before the 4250 can be recalibrated.
2. Load the standard sample prompted by the display into the
freezing chamber and press START. The display will change
to “Cooling Sample”, the operating head will lower, a cali-
bration test will be run, and the results will be displayed and
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