Tektronix TYPE 109, Инструкция по эксплуатации

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Calibration— Type 109
F ig . 6 - 6 . ( a ) P ro p e r a n d (b ) im p ro p er w a v e fo rm d is p la y s . S w e e p ra te is 1 m illis e c /c m . W a v e fo rm s
(c ) a n d ( d ) sh o w the o p e n -co n tact tim e in te rv a ls a t a sw e e p ra te o f 1 0 0 /zsec/cm .
4. Adjust the Biasing Magnet and FREQUENCY
control
a. Set the Type 109 V O LTAG E RAN GE switch to EXT.
PWR.
b. Connect the leads from the mercury switch tester to
the Type 109 connectors as shown in Fig. 6-2. Use
care when inserting the banana plugs into the con­
nectors as explained previously.
The 22-k and 39-k resistors in the tester are used
to produce pulses of different amplitudes across the
10-k load resistor. They also keep the battery drain low.
The batteries are connected in the circuit to produce
pulses of opposite polarity. The two pulses of op­
posite polarity and amplitude make it easy to ob­
serve the operation of the mercury switch under
dynamic conditions.
c. Set the Variable Volts/Cm Switch of the conventional
test oscilloscope to .05.
d. Rotate the Stability control on the test oscilloscope
fully clockwise to obtain a free-running sweep.
e. Ground the probe tip and position the trace to 2
millimeters above the graticule centerline to establish
a convenient zero reference.
f. Connect the probe across the 10-k resistor and adjust
the test oscilloscope triggering controls to obtain a
stable display.
There may be slight horizontal jitter due to mechan­
ical closure of the reed and a spike on the leading
corners of the waveform due to the tester’s lead
lengths.
g. Vary the autotransformer between 105 and 125 (or
210 and 250) volts and check the waveform for the
following characteristics:
(1) Check for a clean, steady waveform display similar
to the one shown in Fig. 6-6a. The closure inter­
val for one set of contacts does not have to be
the same as the closure interval for the other set
of contacts.
(2) Check that the contacts do not bridge; i.e., short
together during open-contact time. If the contacts
are bridging, you will notice that the open-contact
time or step portion of the waveform will move
below the zero reference level to about —0.2 volt
(see Fig. 6-6b). The 0.2-volt change is equal to the
drop across the 10-k load resistor in the tester due
to “ bridging” current.
(3) Check that the contacts remain open for 250 fisec
or longer. To check the open-contact time intervals,
set the test oscilloscope Time/Cm switch to .5
Millisec and the 5X Mag. to O N (or 5X). The mag­
nified step portions should appear similar to those
shown in Fig. 6-6c and 6-6d. Return the oscillo­
scope controls to their former positions.
(4) Check that the closure time is longer than the
open-contact time.
h. If the mercury switch does not operate properly and
produce a clean waveform with desirable character­
istics as shown in Fig. 6-6a and as described previ­
ously, adjust the bias magnet and FREQUENCY
control as follows:
(1) Set the FREQUENCY control to midrange.
6-4