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SVC 5- 29
Calibrate Oven Temperature
To maximize the precision of retention time information, particularly if retention times are to be com-
pared to that of other chromatographs, it may be necessary to calibrate the oven temperature control
circuitry using an independent temperature measuring device.
With the factory- set calibration difference value of 0 (zero), the displayed oven temperature is accurate
to within 1% of the actual temperature (which is expressed in
_
K (Kelvin)).
The HP 5890 Series II provides the means to reset oven temperature monitoring (if necessary) so that
the ACTUAL displayed temperature value accurately represents the correct temperature.
Calibration of the oven temperature control circuitry requires the operator to enter the difference (
delta
)
value (in
_
C) between an independently measured temperature and the corresponding displayed oven
temperature. For example, if the actual measured oven temperature is 148.73
_
C, while the correspond-
ing displayed temperature is 150.00
_
C, the delta value is - 1.27.
Correction Value = Measured Temperature (
_
C) - Displayed Temperature (
_
C)
Setting the Oven Calibration Value
Oven temperature calibration measurements should be made at a temperature in the mid- range of
those temperatures normally attained during operation. Allow ample time (up to 1/2- hour) for thermal
equilibration at the selected temperature. No drift should be observed.
1. Place the temperature sensing probe in the region of the oven which is occupied by the
column(s).
2. Set the oven temperature to the desired level, allowing ample time for thermal equilibration.
3. At the keyboard select the CALIB AND TEST MODE, function 1:
CLEAR
.
1
ENTER
4. CALIB will be displayed, followed by two values; the observed oven temperature (to 0.01
_
C),
and the current delta correction value. Record the current delta correction value. (If problems
occur during recalibration, the value may be re- entered.)
5. Assuming no drift has occurred, the new delta correction value may be entered using the nu-
meric keypad, followed by pressing
ENTER
.
6. CALIB DELTA will be displayed until
ENTER
is pressed again. Then the oven temperature cali-
bration occurs. Note that after oven calibration, the displayed oven temperature value should
closely match the value of the installed temperature measuring device.
NOTE
`
Any delta correction value may be entered within a range of
¦
10.00
_
C. If a value
beyond these limits is entered, the message CORRECTION TOO HIGH is
displayed.
`
Assuming the battery protecting the HP 5890 Series II memory is functional, the
new delta calibration value remains in effect even if the instrument is switched,
disconnected from its power source, or experiences a power failure.
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