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Dynamic Environment Measuring System (DEMS)

The Dynamic Environment Measuring System (DEMS) is an instrumentation package that monitors and records Spacelab vibration, acoustics, and acceleration levels during launch and reentry. Data are used to monitor the stimuli various biological systems experience under launch and reentry loads. A microphone, a triaxial-vibration sensor unit, and a triaxial-accelerometer unit function, respectively, as the acoustic, vibration, and acceleration transducers. One other device, the DEMS MET (Mission Elapsed Time) Slow Code Generator, converts the orbiter's pulse width modulated time code (100 Hz) to an amplitude modulated "slow code" (10 Hz) which is recorded by the DEMS tape recorder.

The DEMS Signal Conditioner passes only certain frequency ranges from the sensors to the recorder. The axes and frequency ranges of the various signals are as follows:

Acceleration: X,Y, and Z axes, low frequency only (DC-20 Hz) for three unique signals.

Vibration: X,Y, and Z axes, low and high frequencies (20-160 Hz, 50-2,000 Hz) for six unique signals.

Acoustics: low and high frequencies (20-160 Hz, 50-6,000 Hz) for two unique signals.

MET Slow Code: low frequency (10 Hz) for one unique signal.

During launch and re-entry, the DEMS cassette recorder collects the signal on two cassette tapes, seven tracks per tape (the eighth channel is not used). The twelve DEMS signals are distributed on the two cassette tapes within the DEMS; X-acceleration and MET signals are recorded on both tapes to help synchronize the two separate groups of data. The DEMS is designed to activate automatically at launch and re-entry, but can also be manually controlled. Once activated, the DEMS records data automatically for ninety minutes.

Versions of this Hardware
+ As Flown on SL-3