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# Tachometer display conflict

## Tachometer display conflict

(OP)
So, having a long commute allows me to spend countless hours in my car, inevitably staring at my dashboard while stuck in traffic. In doing so, I took a rather detailed look at my speedometer and my tachometer and noticed that the they did not seem consistent in the information display to the driver.

To start with, the speedometer is in miles per hour, the number you read is just that......mph.

The display of the tachometer seems a little backwards. When I read "3", that means 3000 rpm. Hence, one must multiply 3 by 1000 to obtain the correct rpm. BUT....when you read the little note, it says "RPM*1000". I contend that this is completely backwards. 3 = rpm/1000. 3 does not equal rpm*1000.

The rub is that when I read the speedometer, say 70 IS mph. But when I read the tachometer, 3 IS NOT rpm*1000. To be correct, it should read rpm/1000.

Now go easy on me, I am a structural guy. And yes, I know that this is the way every car has been done since day one, but it seems mathematically incorrect. Do you see my point?

### RE: Tachometer display conflict

It's just semantics. As you say many meters have always been this way. You need to modify your thinking to match reality rather than argue about it.

### RE: Tachometer display conflict

What if you were to read that little scrap of information as the following:

take what this "RPM" gauge is indicating and do a "x 1000" to it . . . and because we aren't going to clutter the face of this gauge up with all those zeroes we're telling you how to make sense out of what it does read.

Norm

### RE: Tachometer display conflict

Engineering notation. Reading x 103 = RPM.

Problem is, they allow non-engineers to drive cars.

je suis charlie

### RE: Tachometer display conflict

I don't see the point, the units just go behind the gauge reading.
It's not 3=rpm*1000, it's 3rpm x 1000 = 3000rpm.
Same as it's not 50=mph, it's just 50mph.

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