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Checking and adiusting
GENERAL
INFORMATION
The tolerances mentioned are factory tolerances; they
apply when the apparatus is readjusted completely.
They may differ from the data given in chapter I.
A summary of the adjusting elements, their nomen-
clature and location has been given in chapter IV.
With the aid of these data, it is possible to carry out
all the adjustments of low drift unit PM 3332 and
to check the proper working of the plug-in unit. For
this the unit should be inserted into the Y-plug-in
compartment of a correctly adjusted basic oscillo-
sc op e P M 33 30.
Some of the adjusting elements are on the right-hand
side of the unit and are not directly accessible. When
these elements should be adjusted, the unit should be
connected to the basic oscilloscope via the rigid ex-
tension plug (for the code number of this plug, see
the list of accessories of PM 3330).
For a complete adjustment of the instrument the se-
quence as described in this chapter is to be preferred.
ti,ii:',.:.:,
K:::.:
17
A.
CHECK OF THE CHOPPER.AMPLIFIER
It is possible to remove the chopper-amplifier from
its housing after removing lid 66A" (Fig. 13) and a
four pin plug, a three pin plug and a single pin plug.
If measurements are carried out when the amplifier
is out of its housing, it should be carefully screened
to avoid hum.
Connect the positive pole of a 24 V supply to
earth and to the green wire on the 4 pin plug.
The negative pole should be connected to the
black wire on the 4 pin plug.
Adjust the oscillator frequency to approx 400 Hz
by screwing in or out the core of coil L302.
Apply a I mV negative voltage (with the aid of
a suitable voltage divider and the l2 V power
supply or a separate dry cell) to pin
((
l)) of the
3-pin plug. Connect pin
((2)'
to the "common" of
the voltage divider and earth pin
(s3))
by connec-
ting it to the green wire of the 4-pin plug.
Rl B7
R208
@ @
Fig. 13. Right-hand view
@-
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