1-21. ELECTRONIC STATION (cont)
The front panel interface is the link between the
microprocessor and the control panel.
Interfaces are provided for Up to four 8-digit
displays, thumbwheel switches, and pushbutton switches. A joystick is plugged into a
front panel connector for use during equipment calibration.
(5) STD Bus.
The STD bus standardizes the physical and electrical aspects of the
modularized pc cards used in the temperature control unit.
The standardized pinout
and 56-pin connector scheme lend themselves to a bussed backplane that permits any
card to work in any slot.
The standard bus is dedicated to internal communications.
Peripheral and input/output devices can be connected to the system according to their
own unique connector and cabling requirements.
(6) IEEE STD 488 Interface.
A digital interface conforming to IEEE
standard 488-1978 allows the temperature control unit to communicate with the other
A DIP switch on the rear panel is used to set the IEEE bus 5-bit binary
address of the device.
b. CONTROL UNIT ASSEMBLY 1A1 (ALTERNATE)
Control unit assembly 1A1 (FO-3) is the controller used with three
associated sources to make up an ambient range IR source system.
In order to
describe the function of the controller the complete system is covered, even though
the three heat sources are located in the nightside test bench. Each heat source
contains a bidirectional thermoelectric heater/cooler assembly and a platinum resist-
ance thermometer (PRT).
They are of a special structure and have a black, high-body
sources or blackbody IR emitters; hereafter called emitters.
In addition, emitter A
has a connector from which a cable with a PRT (hereafter called sensor) extends to
sample ambient air temperature.
(2) Ambient Sensor.
The temperature range of the ambient sensor is from 00.00
It is displayed on the
TEMPERATURE °C digital panel meter when the tem-
perature display control switch is set to the AMBIENT position. (
is the delta
symbol, used to indicate change.) Temperature changes cause the resistance of the
sensor to change.
This change is converted to electrical signals in the ambient
sensor amplifier, then applied to the summer and to the combined circuitry of the
temperature display control and the COMPUTER/PANEL CONTROL switch. These signals are
indicated by the
TEMPERATURE °C digital panel meter and applied to the binary-coded
decimal (BCD) output bus and to the IEEE 488 bus interface.
(3) Emitter A.
Emitter A has a 2-inch square radiating surface, precisely con-
trolled in O.O1°C increments.
Emitter A may be controlled automatically to an abso-
lute temperature set point, or it may be slaved to track the ambient sensor.
tracking the ambient sensor, a fixed amount of temperature offset may be added to, or
subtracted from the emitter A temperature (differential temperature).
(a) A temperature setting for either an absolute or differential emitter A
temperature is set on the four-digit EMITTER
TEMPERATURE SET thumbwheel switch.
The BCD output of the thumbwheel switch is converted to an analog signal in a digital
to analog converter and applied to the summer.