TB 9-6625-1493-24
12. Differential Voltmeter AC Voltage Accuracy (Transfer Level)
a. Performance Check
(1) Connect calibrator OUTPUT to TI INPUT and COMMON terminals.
(2) Position controls as listed in (a) through (d) below:
RANGE switch to 1.
(a)
NULL switch to TVM.
(b)
(c)
Voltage dials to 1.000000.
Polarity switch to AC.
(d)
(3) Set calibrator for a 1 V, 400 Hz output.
Adjust TI voltage dials for null
indication on each successively more sensitive position of NULL switch until null indication
is obtained on the most sensitive position. Final TI indication will be between 0.998975
and 1.001025; if not, perform b below.
(4) Set NULL switch to TVM.
(5) Repeat technique of (3) and (4) above for calibrator outputs and TI settings listed
in table 7. If TI final indications are not within the limits specified, perform corresponding
adjustments, using technique of b below.
CAUTION
Table 7 requires progressive increase in voltage output from
calibrator. To avoid damage to TI, ensure TI is set to proper
RANGE before increasing the output from calibrator.
b. Adjustments
WARNING
Remove input voltage before removing dust cover for C401,
C403, C405 and C502 (fig. 1).
(1) Set TI voltage dials to 1.000000.
(2) Set calibrator for a 1 V, 400 Hz output.
NOTE
Use calibrator outputs of 10, 100 and 500 V for 10, 100, and
1000 V TI ranges respectively.
(3) Set TI NULL switch successively to each more sensitive position while adjusting
R503 (fig. 1) for null indication on TI (R).