4A3. When the temperature is below 26K (60 psia on
associated circuit) is a pre-calibrated part. Either section
gage) the hydrogen pressure gage is an accurate
(1M2 or 2A3J2) can be separately replaced, but not
temperature gage and is so calibrated. A second sensor
is a thermocouple mounted at the same cold station of
Second Stage Paramp Module 2A2
4A3 as is the hydrogen bulb. The voltage on the
thermocouple leads is brought out to a connector
To maintain constant amplifier stage gain the
(2A3J1). The voltage is then applied through cable
temperature of the second-stage (2A2) paramp circulator
connections to Temperature Monitor 1A1 (a dc amplifier)
and paramp varactor is held constant at 135F (fig. 2-1).
located in Unit 1. The thermocouple voltage is amplified
This is accomplished by use of three 100-watt heaters
sufficiently in 1A1 to drive CRYOGENIC TEMP meter
and a temperature controller circuit that operates from
Temperature Monitor 1A1 utilizes an IC
operational amplifier (para 2-7d) that requires + 12 volts
The temperature controller employs a sense detecting
and -12 volts for operation. The amplification is adjusted
circuit mounted on a circuit card assembly, a thermistor
so that CRYOGENIC TEMP meter 1M1 indicates 20K
mounted on the part whose temperature is being
when the temperature gage on 4A3 also indicates 20K.
regulated and a high-current thyristor (triac) also
The two temperature indicators may not track precisely
mounted on the circuit card assembly. The operating
at other temperatures (20 5K) but the 4A3
temperature is set by adjusting a potentiometer in the
temperature gage is the more accurate of the two.
sense detecting circuit. The thermistor senses a change
c. VACUUM Meter IM2. The vacuum sensor
in temperature and produces a change in voltage in the
consists of a thermopile bridge tube (J2, fig. 2-2) that is
sense detecting circuit. The change in voltage drives a
inserted into 2A3. The sensor uses 0.20 Vac to heat the
low power switch that, in turn, drives a high power switch
hot junc- tions of the thermopile; the cold junctions are
(triac) that switches power to the heaters. A thermostat
held at ambient vessel (2A3) temperature.
is used in series with the heaters to prevent uncontolled
temperature differential between the hot and cold
heating if the control circuit fails. The thermostat opens
junctions is about 10C at atmospheric pressure but
the power line circuit when the temperature reaches
rises to perhaps 400C in a hard vacuum.
150F and closes the circuit when the temperature drops
thermopile (vacuum sensor) then generates an
below 150F. A panel indicator lamp (2A2DS1, fig. 3-
increasing voltage as the pressure decreases. The
14), across the thermostat terminals, lights when the
thermopile voltage is applied to a vacuum gage circuit
thermostat is open, thereby indicating a malfunction in
that drives VACUUM meter 1M2. The complete sensor
the temperature controller circuit.
(thermopile tube 2A3J2 and VACUUM meter 1M2 with its
Figure 2-3. Block Diagram of Temperature Controller Circuit.
2-1). For consistent operation
of the pump waveguide
Pump Source Module 2A1 Temperature
components, they are maintained at a constant
For efficient operation and long life of klystron oscillator
2A1V1, it is necessary to operate V1 at about 195F (fig.