Human Humalyzer 2000 - Calibration

30 Rev.B
Calibration
This instrument relies on software calibration, that is, on calibration data stored in non-volatile
RAM. This data is used by the microprocessor to compensate for variations in electronic
_ components and manufacturing. During factory calibration, the calibration data is set and any
hardware adjustments are made using precision reference standards. The calibration data is then
recorded on a label located on the bottom of the instrument. The factory calibration is very
stable and does not drift appreciably over time, making timpot or other component adjustments
unnecessary unless the trimpots are disturbed or calibration-related components replaced.
Recalibration of the instrument, software or otherwise, should not be considered until all possible
interfering factors have been ruled out. If field calibration is in fact necessary, it should only be
performed with the proper reference materials and instruments. In any case, software calibration
should be attempted before any trimpot or component replacements or adjustments are
considered.
The temperature calibration data is stored as offsets which the instrument adds to the sensed
temperatures. Separate offsets are maintained for the incubation block and the read weil. The
absorbance calibration data is stored as a scaling factor, which is the ratio of a known reference
absorbance to the instrument's reported absorbance. The calibration data may be printed at any
time by selecting test #213. This prints the serial number of the instrument, the date of last
calibration, and the stored calibration data for the absorbance, block temperature, and cell
temperature.
The calibration data is stored with a check sum that is recalculated and compared each time a
mode is selected. Failure to recover the calibration data properly (checksum failure) will be
indicated on the display and the internal printer:
Do Temp Test 210!
Do Abs Test 212!
The instrument annunciates this condition with multiple beeps. The temperature offsets for both
the incubation block and the read well are then set to 0.0 and the absorbance scaling factor is set
to 1.000. In this condition, the maximum temperature error is +/-1.5 °C and the maximum
absorbance error is +/-10%. The calibration data can be restored as described in "Restore
calibration”.
The hardware calibration of the instrument in time is based on a 2 MHz ceramic resonator
RESI.
Calibration
in
temperature
is
based
on
C24,
a
0.068pf
polystyrene
capacitor,
trimpots
TP4 and TP5, and time. Calibration of absorbance is based on C16, a 0. 1pf polystyrene
capacitor, trimpots TP2 and TP3, and time.
Humalyzer 2000 Service Manual