Dynamometer plans/schematics

Back on 7/16/04 I started a thread on homebrew dynamometer ideas that may be of some help. I have not yet completed the project, but the basic idea I had was to couple the driveshaft (or rollers) to a generator and apply a variable PWM load to a resistor bank (such as an electric furnace) to provide a measure of horsepower (or kW). You need to take into account the efficiency of the generator (or measure its temperature rise) for better accuracy. The torque is a little more difficult, but could be accomplished with digital scales. If this is an automotive application, you could put scales under the front wheels, and measure the difference in weight and the distance from the back wheels. You can also measure the RPM fairly accurately so you have a third value to make sure the data seems reasonable.

There should be various sensors available that convert weight, RPM, and wattage to A/D friendly signals like 0-5 VDC. There are numerous data collection packages available for serial, parallel, USB, etc. Most software is essentially like a digital chart recorder for each value. You may need to process the data to get a readout of torque, power, and velocity based on the sensors you have, in units you want.

Good luck!

Paul E. Schoen, President P S Technology, Inc. Cockeysville, MD 21030-2824

60 tooth wheel and mag pickup would work. Frequency will be the same as the RPM. Can use a F to V if you need an analog signal.

Probably have to write your own. Suggest you do some more reading on inertial dynamometer theory. Try here:

For a frequency input you might be able to use a sound card or a zero crossing detector (radio guys use them for RTTY decoding)