Operation & Service Manual
Section III
Model 1805B RF Control Unit
Theory & Operation
GENERAL OPERATING CONSIDERATIONS
All equipment should be operated from a regulated ac supply. Allow at least one hour for
electronic equipment to warm up before any measurements are made. When operated
from a cold start, the RF Transfer Standard used with the Model 1805B will require at
least two hours to reach temperature stability under control of a temperature controller.
This is accomplished by placing the POWER switch in the STANDBY position for the
first hour and a half and then the ON Position for the last half hour with the RF ON/OFF
switch in the OFF position.
During calibration runs, ensure that the Model 1805B BRIDGE BALANCE meter is
zeroed prior to each calibration with the RF ON/OFF switch in the OFF position.
Temperature variations within the laboratory should be held to a minimum to avoid
excessive temperature fluctuations within the sensor or instrument under test
All equipment should be operated on a laboratory work bench as firm and solid as pos
sible.The thermistor mounts should be used on a smooth surface, such as 1/8" sheet of
nylon plastic, to improve ease of positioning. Components should be supported at prop-
er intervals to avoid misalignment.
Connectors must be properly aligned. Center lines must be coaxial; connector faces
must be parallel and must meet neatly and firmly. When the coupling nuts are engaged
and the connector starts to seat, the mount should be wiggled slightly as the connector
is tightened to ensure accurate seating. The recommended torque applied to the cou-
pling nut is 7-10 inch/pounds.
Figure 3-1 Controls and Indicators (Front)
CONTROLS AND INDICATORS
The following paragraphs provide a description of all controls and indicators located on
the Model 1805B. Figure 3-1 shows the location of all the switches and indicators on the
Model 1805B.
3-2
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