Calibrating An Ac Voltage Source - Fluke 540B Instruction Manual

540B
STEP CONTROL
POSITION OPERATION
a
POWER
ON Set the RANGE switch in a position that will cause
GALV
OPEN
the PERCENT INPUT meter to indicate close to,
SENSITIVITY LOW
but not exceed, 100% for the level to be calibrated.
RANGE
Adjust the de source voltage to the exact rms value
MODE
DC SEARCH
of the ac voltage to be calibrated. (Note PERCENT
INPUT meter indication. )
b MODE
DC TRANSFER
Tap the GALV switch against the spring tension to
GALV
MOMENTARY just long enough to see
if
the GAL-
REFERENCE
COARSE
VANOMETER needle will stay on scale. Adjust
ADJUST MEDIUM
the COARSE and MEDIUM controls until a zero
reading is obtained.
c GALV
OPEN Adjust the GALV ZERO control for zero reading
SENSITIVITY MED
on the GALVANOMETER.
GALV ZERO
d GALV
LOCK
Adjust the MEDIUM and FINE controls for zero
REFERENCE MEDIUM reading on the GALVANOMETER.
ADJUST
FINE
e
GALV
OPEN Adjust the GALV ZERO control for a zero reading
SENSITIVITY HIGH.
on the GALVANOMETER.
GALV ZERO
--
f GALV
LOCK
Adjust the FINE control for a zero reading on the
REFERENCE
GALVANOMETER.
ADJUST FINE
g GALV OPEN
SENSITIVITY
LOW
h MODE AC SEARCH
Adjust the ac level to be calibrated until a reading
is obtained on the PERCENT INPUT meter that is
equal to the reading obtained and noted in step a.
i
MODE AC TRANSFER
NOTE: DO NOT ADJUST THE REFERENCE
ADJUST CONTROLS IN THIS MODE.
j SENSITIVITY
LOW Tap the GALV switch against the spring tension to
GALV
MOMENTARY just long enough to see
if
the GAL-
VANOMETER needle will stay on scale while adjust-
ing the level of the ac to be calibrated. When an on
scale reading is obtained adjust the ac level for a
zero reading on the GALVANOMETER.
k GALV LOCK Further refine the adjustment of the ac voltage until
SENSITIVITY
MED a GALVANOMETER reading of zero is obtained in
HIGH
the MED and HIGH SENSITIVITY positions. Record
the ac voltage source setting.
1
Repeat steps b through k at least three times or until repeatibility is attained. Make note of the
ac source setting.
m
Reverse the input polarity to the thermocouple by depressing the POLARITY switch. Repeat steps
b through k at least three times or until repeatibility is attained. Make note of the ac source setting.
n
Set the ac source voltage adjustment in the center of the two settings recorded in steps
l
and m.
The rms value of the ac voltage now equals that desired.
Figure 2- 7. CALIBRATING AN AC VOLTAGE SOURCE
2-9