e-man

I want to use this little device http://www.dataq.com/products/startkit/di194rs.htm to plot wide band O2 vs RPM but I need to convert the rpm signal to volts so the dataq can plot it.Im no electric wiz so it has to be a simple circuit or I was thinking of just buying a aftermarket digital tach and hoping the display runs off of a voltage of 0-10v.If any body knows how to I could work this out let me know.

e-man

Can somebody that is good with circuits looks at this and tell me what circuit would be easyest to make to change the tach out put to volts. http://www.national.com/ds/LM/LM2907.pdf

Kaiser

Some info on h/w & s/w solutions here:

http://forums.corvetteforum.com/zerothread?id=374249

jwscab

The very first tachometer circuit, or the circuit showing an 8 cylinder example would work for you, although it may not give you a full scale 10V output. I don't know if that is really necessary, since the data aq. unit has 10 bit resolution. If you need to rescale the output of the freq-volt converter, use an op-amp in a non-inverting config, with a gain based on the output voltage. for instance, if the full scale out is 6v, and you want 10 v, the gain would be 10/6, or 1.6. You probably wouldn't need that to chart data, because you can alway assume that 6 volts = some freq. determined by the circuit you build, which correlates to max rpm. If you use 6500 rpm, and the application example, 6v=~406Hz, or 67Hz/V. Hope that helps. the application circuits are pretty straightforward, if you're good with following the schematic and a soldering iron, you should have no trouble.

e-man

OK say I make the first circuit and I get more than 10V could I just put a trimpot on the output to get it lower?

jwscab

With the first circuit, and a v-8, you wouln't hit 10 v until well over 10,000 rpm, so you wouldn't have to worry about it, and a smaller cylinder engine is even higher rpm. You could use a trimpot to scale the voltage, if you needed to.

e-man

jwscab thanks for your help when Im done Ill let know how it works out.