Advanced Instruments 4250, Руководство пользователя

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for drift over time or temperature (by temporarily replacing the sample
probe with a precision resistor).
On entry, the A/D tests will display
“ [Start] Ready? ” .
At “ [Start] Ready? ” , pipette or measure a sample of 600 m°C standard
into a sample tube, place the tube in the freezing chamber, and press the
START key.
On entry, the A/D tests display the target cooling block temperature, the
channel being read, and the current channel reading or duty cycle. The
display is in the form, “ off Blk NNNN.NN ohm ” , where “ off ” indicates
that a target temperature has not yet been selected, “ Blk ” indicates that
the block probe channel is being tested, “ NNNN.NN ” is a numeric read-
out of the probe, and "ohm" indicates the units of the readout. These
readings are updated continuously.
Pressing the
< key sequentially changes the target cooling well block
temperature from “ off ” to “ +1 ” , to “ -8 ” , in steps of -1°C to “ off ” , etc. The
sample head will rise when temperature is set to “ off ”, and lower at any
other setting.
Pressing the
> key sequentially changes the channel and readout units
from block probe resistance in ohms, to sample probe resistance in
ohms, to block temperature in tenths of a degree Celsius, to sample tem-
perature in tenths of a degree Celsius, to cooling block duty cycle ( “ NN
% ” on), to block resistance in ohms, etc.
CAUTION The temperature values displayed are based on the block
probe resistance which the instrument is configured for.
Thus, if the block probe bin number has been incorrectly
set, both the displayed temperatures and resistances will be
incorrect, as well as the actual temperature of the sample
cooling well.
While the target temperature is “ off ” , the block probe is warm and its
resistance should be less than 4,990 ohms. As the temperature is set
colder, the resistance will increase.
Press
STOP to raise the operating head and exit to the test menu.
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Troubleshooting & Service