Advanced Instruments 4250, User Manual

Page: 43 / 121

21
Instrument Operation
At the “ I.D. # ” prompt, the present setting may be retained by press-
ing ENTER .
The present setting may be erased entirely by pressing CLEAR, or
erased one digit at a time from the right by repeatedly pressing < .
A new number may be entered one digit at a time from the left via
the numeric keypad, unless the number was input from a barcode
scan or was already accepted in a previous test, in which case press-
ing < will erase the whole number.
7. Press ENTER to store the new setting and continue the test. “ Press
START to Continue ” will begin to scroll across the display.
8. Press START (pressing STOP would cancel the test).
The rest of the test is completely automatic. The operating head will
lower the sample probe into the sample tube in the freezing cham-
ber. The fan will come up to full speed and the freezing chamber
will cool.
The sample temperature will follow the freezing curve shown in
Figure 1 and will be displayed as soon as it falls below 0°C.
The 4250 will freeze the sample at a fixed crystallization point, fol-
low the plateau development, determine the freezing point as
defined by the SETUP program, and lock the result on the display
and in the RECALL buffer.
NOTE
• If the STOP soft key is pressed while a test is in
progress, the test will be discontinued and the 4250 will
reset itself for the next test.
• Sample ID# information will be printed on the printout
and presented via the RS-232 port at the end of the test.
9. When the display reads “ Freezing Pt xxx mC ” (or xxx mH ), the
test results may be recorded.
10. Remove the sample tube from the cooling well.