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DIGISONDE-4D
SYSTEM MANUAL
VERSION 1.2.11
6-16 SECTION 6 - MAINTENANCE
BUILT-IN TEST: PERIODIC SELF-DIAGNOSTICS
6:58. The Built-In Test diagnostic system is comprised of a set of hardware sensors, a BIT card with a micro-
controller that digitizes the sensor data, and the BIT program software. The BIT program uses measurement da-
ta in addition to the data collected by the BIT card to determine the health of the system. There are three types
of BIT sensors. Digital (Go/No Go) sensors are used to monitor power supplies and over-temperature condi-
tions. Static Analog sensors are analog signals that are always present such as temperature signals. Dynamic
Analog sensors are signals that are present only during sounding.
Sensors collected by the BIT Card:
• Power Distribution card power for Preamplifier/Polarization Box (digital)
• Power Distribution card –15V, -5V, +3.3V, +15V, +12V(digital)
• Power Distribution card over-temperature condition (digital)
• Power Amplifier power for first stage amplifier +18V (digital)
• Transceiver Chassis Temperature (static analog)
• Power Amplifier Chassis Temperature (static analog)
• Transmitter card channel 1 & 2 output (dynamic analog)
• RF Power Amplifier channel 1 & 2 output (dynamic analog)
• Saturation sensor from Tracker #4 (digital)
Other measurement data collected and used by the BIT program:
• Receiver card channel 1, 2, 3, 4 output (dynamic analog, “routine data”)
• Hardware Test Pattern from Pre-Processor (digital, gathered by DESC)
• Parallel Bus Data Timeouts (digital, determined by DESC)
6:59. Figure 6-12 shows the location of the sensors and data collection points.
6:60. The BIT program puts the system in four different configurations (cases) using switches in the antenna
switch, tracker cards, and RF amplifier output switching to make a determination about system health.
6:61. Case 1 is external loopback (Figure 6-13). The system transmits normally as though making a meas-
urement. The signal enters the receivers through the antennas. The program listens at 0 km height for the trans-
mit pulse.
6:62. Case 2 is internal loopback (Figure 6-14). A low level calibration signal from the digital transmitter is
routed through the antenna switch to the inputs of the tracker cards.
6:63. Case 3 is internal loopback with tracker cards bypassed (Figure 6-15). A low level calibration signal
from the digital transmitter is routed through the antenna switch to the inputs of the tracker cards. Switches on
the tracker cards connect the inputs to the outputs, effectively bypassing the bandpass filters.
6:64. Case 4 is transmission into dummy loads (Figure 6-16). The system transmits normally but the RF
output from the half octave filters in the power amplifier are routed to dummy loads rather than the transmit
antenna. The health of the transmit antenna can be determined by comparing the levels of the RF 1 & 2 sensors
with the results from Case 1.
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