MM0474
b. Applications include self-contained power measurement, precision power
measurement
and
reference
level
thermistor
mount
factor
certification.
c. Procedure for thermistor mount calibration factor (Kb) certification at
secondary reference level.
(1) Equipment connections.
Figure 6.
(2) Techniques.
(a) Make equipment setup as shown in Figure 6, connection "A".
(b) Set switch to direct power to cavity frequency meter.
(c) Energize signal source
and
tune
for
desired
frequency
as
indicated on cavity frequency meter.
(d) Null both NBS II Power Bridges using following procedure:
1.
Pre-operation setup.
a. With instrument turned off, set BARR-THER switch
according to type of bolometer mount being used.
If this switch is not set
properly it is possible to destroy a bolometer element, particularly a
barretter. Turn instrument off before changing the switch setting.
b.
Attach lower links as appropriate for mount operating
c. Rear grounding link should be in place unless it is
necessary to float instrument above ground.
d.
Bolometer
mount
may
now
be
attached
to
bridge
and
instrument turned on.
2.
Nulling procedure.
Note -
This measurement requires the use of an external voltmeter.
The
accuracy of this voltmeter should be the best possible, since its error
contributes directly to the overall measurement error. The voltmeter
should be connected to binding posts 21 and 22 located on the lower
part of the reference generator.
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