Measuring and Telemetry
Approximately 200 parameters were measured on the IU and transmitted to the ground, in order to
- Assist in the checkout of the launch vehicle prior to launch,
- Determine vehicle condition and to verify received commands during flight, and
- Facilitate postflight analysis of the mission.
Parameters measured include acceleration, angular velocity, flow rate, position, pressure, temperature, voltage, current, frequency, and others. Sensor signals were conditioned by amplifiers or converters located in measuring racks. There are four measuring racks in the IU at locations 1, 9, and 15 and twenty signal conditioning modules in each. Conditioned signals were routed to their assigned telemetry channel by the measuring distributor at location 10. There were two telemetry links. In order for the two IU telemetry links to handle approximately 200 separate measurements, these links must be shared. Both frequency sharing and time sharing multiplexing techniques were used to accomplish this. The two modulation techniques used were pulse code modulation/frequency modulation (PCM/FM) and frequency modulation/frequency modulation (FM/FM).
Two Model 270 time sharing multiplexers (MUX-270) were used in the IU telemetry system, mounted at locations 9 and 10. Each one operates as a 30x120 multiplexer (30 primary channels, each sampled 120 times per second) with provisions for submultiplexing individual primary channels to form 10 subchannels each sampled at 12 times per second. Outputs from the MUX-270 go to the PCM/DDAS assembly model 301 at location 12, which in turn drives the 245.3 MHz PCM VHF transmitter.
The FM/FM signals were carried in 28 subcarrier channels and transmitted by a 250.7 MHz FM transmitter.
Both the FM/FM and the PCM/FM channels were coupled to the two telemetry antennas on opposite sides of the IU outside locations 10 and 22.
Read more about this topic: Saturn V Instrument Unit, Subsystems, Radio Communications
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