Fluke 540B - Electronic Galvanometer Calibration

540B
b. GALV switch OPEN.
SENSITIVITY
switch LOW.
POWER
switch ON .
c. Adjust R6 for a 1. 2 ±0.1 vol t peak - to- peak wave-
form displayed on the oscilloscope.
d. Remove oscilloscope connections.
e. Connect an electronic counter between the lead of
R5
nearest Ql and the negative end of Cl.
f. Adjust the core of Tl for a 2500 ±5 Hz indication on
the electronic counter. (The
core of T1 is adjust -
able
from the land pattern side of the circuit board.
Access
to the adjustment is through the opening l eft
from removing the battery pack. )
g.
Remove all test connectio ns and set the POWER
switch to OFF.
h. Re - install the battery pack and top cover on the
Model 540B.
4-16. TUNED CARRIER AMPLIFIER ALIGNMENT.
Remove
the side cover on the galvanometer side of the
Model 540B.
Refer to Figure 4- 4 for adjustment and
connection locations. Connect equipment as shown in
Figure 4- 3 and use a 1 megohm ±1 % resistor for Rx.
Proceed as follows:
a. Connect the oscilloscope vertical input to the junc-
tion of R34
and R35 (junction E) . Connect oscillo -
scope ground to T2 mounting screw.
b. Set the oscilloscope controls for 100 m ill ivolts per
centimeter of vertical deflection and 50 micro-
seconds per centimeter of horizontal deflection.
c. GALV switch OPEN .
. SENSITIVITY
switch LOW.
POWER
switch ON.
d. Adjust power supply for 3 volts ±100 mv (3 ua
input).
e. With a non- metallic screwdriver, adjust the core
of T3 (adjustment H) for a maximum 5 kHz signal
level, as seen on the oscilloscope.
f. With a non- metallic screwdriver, adjust the core
of Ll (adjustment J) for a maximum deflection to
the
right on the GALVANOMETER meter (approxi-
mately 20 ±5% of full scale) .
g. Repeat steps (e) and (f) for a maximum signal indi-
cation on both the GALVANOMETER meter and the
oscilloscope.
4- 17. TUNED CARRIER
AMPLIFIER GAIN. Check
and readjust, if necessary, the mechanical zero of the
GALVANOMETER meter. Connect the equipment as
shown in Figure 4-3 and use a 10 megohm ±1 % resistor
for Rx•
a. GALV switch OPEN.
4-4
SENSITIVITY switch HIGH.
POWER
switch ON
x
(+)
(+)
POW ER
Rl 6
S
UPPLY
G ALVA NO-
METE R
(-)
(-)
CIRCU IT
(+)
DI FFERE NT I AL
VOLT METE R
(-)
Figure 4-3 . EL ECT RO NI C GA LV ANO METER CA LI BRATION
E
R34 / R35
JUNC T IO N
J
L1
A DJ U ST MENT
Figure 4 -4 . TUNED CAR R IER AMPLI FI ER ADJUSTMENTS
b. Adjust the power s up pl y output for 0. 3 volt ±10 mil -
livolts ( 30 na inpu t) .
c. Adjust R36 (adjustment L) for 8 minor divisio ns de -
flection
to the righ t on th e GALVAN OMET ER met e r.
d. Reverse th e po la rity of the po wer su pply and check
the deflec t io n of the GALVAN OMET ER mete r.
Should the de fl ection in st eps c a nd d be un e qual,
adjust R36 f or t he bes t average de fl e ction in both
po l arities (not t o e xceed 8 ±1. 0 mi nor divi s ion s
in either pola r ity ).