MM0474
will provide the proper operating current to D110.
R111 by-passes Q105 to
provide enough signal to D110 to permit the power supply to turn on.
(5) The voltage drop across R104 developed by the load current will
cause Q103 to conduct if the drop exceeds approximately 0.5 volts.
This in
turn causes Q104 to conduct, and Q103 and Q104 together comprise a high gain DC
amplifier. As Q104 conducts, current from Q107 is diverted from Q108 to the
negative output line.
This results in sharp current limiting at the point
where Q103 first begins to conduct.
(6) The P100 printed circuit board was designed for general purpose
applications which might require remote sensing.
In this instrument, the
output voltage is sensed on the motherboard side of the connector rather than
on the P100 side. Diodes D111 and D112 are included for possible applications
where opening one of the sense lines might result in an over-voltage condition
which could damage the attached equipment.
i. 10 Volt Precision Reference Supply Circuit Description. The +10 volt
supply on the V400 printed circuit board (see Figure 16) is essentially
identical to the +15 volt regulator described in Paragraphs 7h(3) and 7h(4).
The +15 and the +30 volts for the 10 volt regulator are obtained from the +15
volt P100 board. A lower temperature-coefficient reference element, Q404, is
used. The temperature coefficient of Q404 may be further improved by adjusting
its collector current through selection of R405.
As Q404 is temperature
cycled, R405 is chosen from a range of values lying between 20K ohms and 287K
ohms to give the best overall temperature coefficient.
Since the output of
this reference supply must be set to better than 10 ppm, a more elaborate
divider string, R409 through R418, is required.
The values of R409, R410,
R415, and R416, and the position of R417 and R418, can only be determined after
knowing the exact value of the reference element voltage.
This may be
determined after the collector current is set for a minimum temperature
coefficient. Short circuit protection is provided by current limiting of the
+15 volt supply.
8.
POWER STANDARDS SET.
a. Description.
(1) The Power Standards Set consists of six power standard assemblies
cushioned with a foam insert and packaged in a lightweight container.
The
power standard assemblies consist of either a waveguide or coax high
directivity directional coupler and thermistor mount. The thermistor mount is
attached and sealed to the coupled output of the directional coupler. The foam
insert acts as a cushion and protects the power standard assemblies from damage
during transportation.
The container protects the power standard assemblies
from environmental conditions during transportation and storage and forms a
convenient shipping container.
128
Previous Page
