Temperature Control
Figure 6-14 is a block diagram of a receiver-
converter heat exchanger.
The heat exchanger
supplies conditioned air to the receiver-converter
assembly for environmental control. The exchanger
shown consists of two blowers, six heaters, three
temperature-sensitive switches, and an air-to-air heat
exchanger. Three of the heaters are connected in a
wye conflguration, and the other three are connected
in a delta configuration.
The three temperature-
sensitive switches are usually mounted on the receiver
casting. Blowers B1 and B2 circulate cooling air and
heating air within the receiver-converter. Internal
blower B1 operates whenever the FLIR system is
turned on.
If the temperature of the assembly
compartment goes above approximately 77°F (25°C),
thermal switch RT3 operates relay K3, applying
power to external blower B2. Blower B2 draws cool
external air through the air-to-air heat exchanger.
Internal blower B1 circulates the cool air and cools
the compartment.
If the temperature in the
compartment goes below 68°F (20°C), thermal switch
RT2 operates relay K1, applying power to the
wye-configured heaters. The heaters operate at
approximately 365 watts. If the compartment
temperature drops below 50°F (10°C), thermal switch
RT1 operates K2, applying power to the
delta-cordigured heaters. This increases the wattage
used by the heaters to approximately 1,200 watts.
Thus, the heat exchanger is able to maintain the
receiver-converter compartment at a temperature
between 68°F and 77°F at all times.
Positioning and Stabilization
The function of the stabilized gimbal subsystem
of the receiver-converter is to allow the operator to
select the line-of-sight (LOS) desired to the receiver
unit. Another function is to maintain a steady image
of the IR patterns of the areas viewed regardless of
aircraft movement. This critical stability is obtained
by means of gyros mounted on the receiver assembly.
There is one azimuth and one elevation gyro.
Figure 6-15 is a simplified block diagram of a typical
FLIR positioning and stabilization subsystem.
Figure 6-14.-Receiver-converter heat exchanger block diagram.
6-12
