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
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
Resistors. 1k
14V in----/\/\/\/----------- 7V out | | / \ 1k / \ | _______________|_________
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:
which you can get here:
Use the chip like it describes in the test circuit in the datasheet.
Regards, Bob Monsen
wonderful, thanks.
Is the RPM reading an analog voltage? It seems that this value would be available as a frequency or pulse width.
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
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:
thanks d1
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