Dear Dennis... analogZONE's Dennis Feucht answers your design queries in his new Circuit Design Clinic! May 2006

analogZONE presents a new, interactive analog design service to readers! Send us your design questions (with relevant data; schematics in JPEG or GIF, please) for some free engineering advice from analogZONE's circuit consultant, Dennis Feucht, on how you might solve a design problem or improve circuit performance. Submissions may be edited for clarity or brevity, and submitters and their email addresses will remain anonymous (unless otherwise indicated). Please send your questions to Dennis here.

Data Acquisition System for Rocket Test Stand

This problem involves data acquisition at a system level, a problem common to users of computer data-acquisition and control (DAQ/C) boards who use them in system-level designs. This DAQ/C user is an astronautical (not astrionic) engineer building a rocket test stand, and he needs to acquire engine data such as chamber pressure and temperature, tank flow rate and pressure and, of course, engine thrust.

Dear Dennis:

We are building up a data acquisition system for our test stand. Attached is a circuit design for a single channel of signal conditioning. The guy who designed it did signal conditioning design previously and has gone off to grad school and I'm looking for advice on how to build up a few circuits to test out with our A/D boards.

Our test stand will evaluate our ability to throttle a hybrid engine. We have a ball valve with a 15° slot cut into it. The flow control is very linear. We found a radio-control servo used for giant R/C models. The torque is over 400 oz-in and costs $120. We plan to start testing with a manual lever and progress to a throttle control system driven by the servo. The throttle is connected to an R/C receiver and we control it with a standard R/C control transmitter. The signal conditioning will measure load cells and pressure transducers.

For Dennis' response and more of this month's circuit design queries, download the current PDF file here.