data logging engine RPM with 10V logger

Hi, I have a DataQ 194 data logger which has four +/- 10v input channels. I want to log the RPM of a car, which is outputting approx

14volts. How can I reduce this voltage so the data logger does not go up in smoke?

thanks Don

Reply to
Don
Loading thread data ...

Resistors. 1k

14V in----/\/\/\/----------- 7V out | | / \ 1k / \ | _______________|_________
Reply to
JeffM

That should work. However, you might want more isolation than that for other reasons.

So, another possibility would be to use an optoisolator chip, like this one:

formatting link

which you can get here:

formatting link

Use the chip like it describes in the test circuit in the datasheet.

Regards, Bob Monsen

Reply to
Robert Monsen

Is the RPM reading an analog voltage? It seems that this value would be available as a frequency or pulse width.

Reply to
Wade Hassler

Most automotive tachometer signals will be a pulse, either square wave or sine wave with the frequency per RPM depending on number of cylinders and whether two or four stroke (usually based on number of sparks per revolution). Diesels & outboard boat motors are another story

Hope this helps, Dennis

Reply to
Barbarian

What I am going to do is build a frequescy to voltage conversion circuit using an LM2917. The circuit is simple and will output less than 10V. A nice voltage graph will be better than looking at RPM pulses to try to figure out the RPM.

Here is the spec on the LM2917:

formatting link

thanks d1

Reply to
Don

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.