Electronics & Connectivity - September 5, 2012 - 5

The VT FSAE car on the test course without body. performance; if you design too light, you destroy your reliability.” According to West, actual operational loads are often “hard to get.” VT began using a torque telemetry system from Accumetrics Associates that could help the team compile a dynamic load history. Accumetrics has much experience helping organizations that need to make measurements on rotating equipment. General Motors, for example, used an Accumetrics system in the development of the Cadillac CTSV racecar. The AT-5000 telemetry system that VT used was designed to be easily applied to rotating shafts with Kevlar straps and to run for long durations on its internal battery. Its transmitter mounts opposite an equally weighted adjustable yoke to maintain balance, and only about 0.7 to 0.9 in (18 to 23 mm) of radial clearance is needed around the shaft. The Kevlar strap has a breaking strength of 3000 psi and can withstand up to 20,000 rpm, depending upon shaft diameter. Battery life can be as long as 150 hours on a single lithium battery when used with a 1000 ohm full bridge strain gage. The system can accommodate other sensor signals, including voltages and thermocouples and can sample data at 7812 times a second or faster. Receiving antenna options include a rigid brass loop, a flexible loop, and a miniature
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The Accumetrics AT-5000 transmitter mounted on a halfshaft. stub antenna. By gathering data on the rotor and digitizing it before transmission, the AT-5000 EasyApp telemetry system provides high accuracy and resolution even in the face of noise sources such as ignition spikes. The AT-5000 receiver converts the transmitted torque signal digital data to a simple ±10-V output. If rpm is also monitored, the torque and rpm data can be combined to show instantaneous delivered horsepower. “We need to get a dynamic history of what loads
September 5, 2012

Electronics & Connectivity - September 5, 2012

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