Analog Meter capability

[Joe Boucher]

Tom Cloud wrote:
> 
> >I was thinking about setting up a GM MAP sensor on my Camaro, complete
> >with a 5 volt signal, and trying to obtain some data relating manifold
> >pressure to throttle position and RPM.
> 
> what's wrong with a plain ole vacuum gauge ??  -- or are you wanting
> a "real" electronic signal ??


I'm trying to get some data from the Camaro to start designing the op
amp circuit.

 
> >Would an analog meter with 10k internal resistance require more power
> >than the sensor would put out?  I have a small 10 meg internal
> >resistance voltmeter, but I don't think this would work well. The
> >digital meter display wouldn't settle down enough to take readings.  The
> >analog would tend to dampen out some fluctuations.
> 
> first you say 10k and then 10M  --  I, personally, don't have a
> clue as to the Zout (output impedance -- or ability to provide current)
> of the MAP sensor.  I'd suspect that it was lower than that of the
> EGO sensor though.


I have two meters, one is analog, one is digital.


> 
> typical DMM has 10M Zin.  typical VOM has 20k ohms/volt (unless you
> get it from ratshack .... then maybe 5k or 10k ohms/volt.  If the
> analog meter has an internal amp (does it need batteries for more
> than the ohms scale ?), then it will likely also have 10M Zin.

It requires AA's and a 9 volt battery.  I haven't tried it without the
batteries in it to see what does and doesn't work.
 
> The analog meter would definitely "smooth out" the reading so
> you can more easily see trends, etc.
> 
> Here's how to find out the answer to your question:  put a known
> vacuum on the sensor and measure it with the DMM.  Then, measure
> it with your analog meter and see if it's significantly different.
> (Of course, if the Zin is 10M then there's no reason to do this,
> it should work okay.)

I have one of those hand vacuum pumps.  I'll try it.
 
> Tom Cloud
> 
>      Madness takes its toll   .....   please have exact change