Fluke 540B - Periodic Maintenance; Search Meter Calibration; Protection Amplifier Calibration; Galvanometer Calibration

4-9. PERIODIC M A IN TENANCE
4 -10. SEARCH METE R CALIBRATION
4-11. Calibr ation of the search meter circuit requires
sources of 10 and 0. 5 volts de, and rms ac at 500Hz
and 1 MHz, with ±1. O% accuracy . Remove the bottom
cover from the Model 540B and proceed as follows:
a. MODE switch to OFF.
b. Connect a +10 volt de source to the INPUT DC con-
nectors on the A54 p lu g -in unit.
c. POWER switc h ON.
RANGE
switch 10 volts.
MODE swi tch to DC SEARCH.
d. Adjus t R318 to obtain 0. 5 volts (±1 mv) de on the
differential volt meter between the anode of CR312
and the chassis. Read and record the search meter
reading (100% ±10%) .
e. Connect a +0. 5 volt de source to the INPUT DC con-
nectors of the Model A54 plug - in unit.
f. RANGE switch 0. 5 volts .
g. Read and record the search meter reading. Adjust
R318 to obtain a sea rch meter reading equal to the
average value of the readings recorded in steps d
and g.
h. MODE switc h OFF.
i. Disconnect the 0. 5 volt de s ou rce and connect a
0. 5
volt rms ac, 500 Hz source to the INPUT AC
conn ector on the Model A54.
j. MODE switch to AC SEARCH.
k. Adjust R310 for a 100% reading on the PERCENT
INPUT meter.
l. MODE switch to OFF.
m. Connect a 0. 5 volt rms ac, 1 MHz signal to the
INPU T AC of the Model A54,
n. MODE sw it ch to AC SEARCH.
o. Adjust C305 for a 100% reading on the PERCENT
INPUT meter . Th is completes the calibration of
the search circuit in the Model 540B.
4-12. PROTECT IO N AMPL IFIER CALffiRATION
4- 13. Remove
the bottom cover from the Model 540B.
Proceed as follows:
a. MODE switch to OFF.
RANGE switch to 0. 5 volts.
POWER switch to ON.
b, Locate R314 and tu rn f ully clockwise.
c. Connect 0.73 ±0.01vo lts de to the DC INPUT termi-
nals .
540B
d. MODE switch to DC SEARCH.
e. Rotate R314 counter-cl ockwise until the protection
circuit operates, causing the PERC ENT INPUT
meter to deflect to the OVERLOAD area. The pro-
tection circuit should operate within 0. 70 to 0. 75
volts de at the DC INPUT terminals.
f. Remo ve the de input voltage.
g. Reset the protection circuit by setting the MODE
switch to OFF and then back to DC SEARCH.
h. Apply a -0. 70 volt s de to the DC INPUT terminals.
Increase the input voltage in 0. 01 volt de steps until
the pro tection circuit operates. The protection
circuit should operate between 0. 70 and 0. 75 volts
de.
i. Adjust R314 until the protecti on circ u it operates in
both polaritie s of the de input wi thin 0. 70 to 0. 75
volts de.
j . Remove the de input voltage.
k. MODE switch to OFF.
l. Connect the output of an oscillator , se t to 1 kHz
at zero volts, to th e AC INPUT connector. Monitor
the oscillator output with an ac voltmeter.
m. MODE switch to AC SEARCH.
n. While observing the ac voltmeter, increase the
oscillator output amplitude until the protection cir-
cuit operates. Record the output voltage of the
oscillator, observed on the ac voltmeter, at the
time of prote ction circuit op er ation.
o. Reduce the oscillator amplitude to zero volts. Reset
the protection circu it by setting the MODE switch
to OFF and then back to AC SEARCH.
p. Repeat step s k throu gh o at 10Hz, 500kHz, and
1 MHz. The protection circuit should operate be-
tween 0. 60 and 0. 75 volts rms ac at all frequenc ies.
q . S et the MODE switch to OFF and remove all test
equipment.
r . Pl ace th e bottom cover on the Model 540B.
4-14. GALVANOMETER CALIBRATION
4-
15 . OSCILLATOR AMPLITUDE AND FREQUENCY.
Set the POWER s w itch in the OFF positi on. Remove
the top co ve r on the Model 540B. Remo ve the screws
securing the battery pack to the Model 540B. Carefully
slide the battery pack out of the Model 540B and place
the pack in such a pos ition as n ot to cause undue stress
upon the connecting wir e harness. Proceed as follows:
a. Connect an oscillo scope v ertical input to the lead
of R5 nearest Ql. Connect the oscill oscope ground
to the negative end of Cl.
4-3