Amplifier for timing light inductive clamp

[ka6772]

I'm trying to use an inductive clamp from a timing light to pick up RPM signals for a chassis dyno. I need <10V but enough for the Dataq DI-148U I'm using to read. I've tried finding a usable signal off the timing light itself, and an AD8230 in-amp in a couple different configurations. With the amp I get a signal but it makes no sense. I'm using the AD8230 in-amps for bridge and thermocouple measurements.

http://www.analog.com/UploadedFiles/Data_Sheets/AD8230.pdf

The data sheet made that easy. Could one of you point me to a suitable amp and schematic for what I'm trying to do?

Thanks,
Kevin

 

[MikeHalloran]

It might help to know which timing light you're working with.



Mike Halloran
Pembroke Pines, FL, USA

 

[ka6772]

It's an Actron CP7504.

Thanks,
Kevin

 

[MikeHalloran]

The Dataq DI-148U is meant to read relatively slow moving voltages, not the frequency of pulses.

You can get a frequency signal with the DI-8B45 plugged into the DI-718B-U.

If you're into electronics, you could probably use the timing light signal to trigger a one-shot, send that to a leaky integrator and low-pass filter, and read that for a ~DC signal that's roughly proportional to engine speed. If your labor is worth anything, it would be cheaper to just buy the DI-718-U and DI-8B45.



Mike Halloran
Pembroke Pines, FL, USA

 

[ka6772]

I hadn't thought of that. The most I could get out of it was about 9hz no matter how high the rpm was. On an hei, I got consistant sharp peaks. On a wasted spark it was small and varied between plug wires. I'll turn up the sampling rate first to see if it helps at all. Then I'll hook to the tach signal to see if the dataq can hang. I have an Opto22 snap ethernet I/O with an IDC5D and an AIARMS. If I can get one of those modules to work, it may be cheaper for me to find a snap adc module for the load cell. I bought the dataq because the whole thing was cheaper than the cheapest snap modules.

Thanks,
Kevin