# How much amperage can an alternator support? no really...

Mark R speedracer.mark at gmail.com
Thu Feb 7 10:23:29 PST 2008

```They aren't necessarily that expensive.  Extech MA120 (or MA-120?).  \$80.00
and measures up to 200A DC current.

Mark Rosenkrantz

On Feb 7, 2008 4:51 AM, syljay <syljay at optonline.net> wrote:

> Huw,
> Now you got me curious. So, I looked it up.
>
> "For non-contact DC current measurements, the probe wraps around the
> current-carrying wire, but instead of a current transformer, there is
> a small gap in the magnetic metal (of the probe) that has a
> Hall-Effect sensor in the gap. DC current will produce a non-varying
> magnetic flux, but the Hall-Effect sensor will measure it's strength.
>
> The magnetic strength is proportional to the DC current, and either
> analog or digital processing can calculate the current from the
> specifications of the Hall sensor, the probe dimensions, etc.
>
> The wiki article has a good graphic about 1/2 way down the article:
> http://en.wikipedia.org/wiki/Hall_effe... "
>
> Good site explaining the differences between AC and DC current
> measurements using clamp style meters - with diagrams.
> http://www.kew-ltd.co.jp/en/support/mame_02.html
>
> So, we were both right.
>
> The normal run-of-the-mill DMM used by electricians wont measure DC
> current via the clamp. One has to spend more money to get a clamp
> meter that measures both AC and DC currents.
> Fluke has seven clamp meter models. But, only 2 measure DC current.
>
>
> SJ in NJ
>
> ---------------------------------------------------
>
>  >> Inductive current meters depend on expanding and collapsing
>  >> electromagnetic fields - - as in A/C current.
>  >>
>  >> A current thru a wire produces a magnetic field around the wire.
>  >> Passing a wire thru a magnetic field produces current in the wire.
>  >> A stationary wire in a stationary magnetic field produces nothing in
>  >> the wire.
>  >>
>  >> DC current will produce a field around a wire . . .but the field
> stays
>  >> constant. No expanding and collapsing fields to produce current in
> the
>  >>   meter inductive pickup - hence, no reading.
>  >>
>  >> Correct me if I'm wrong.
>
>
> I think you might be wrong, based on "personal experience".
>
> I agree that it is much easier to measure AC via inductive tools than
> DC, but I did see it done.
>
> -- Huw Powell
>  _______________________________________________
> quattro mailing list
> quattro at audifans.com
> http://www.audifans.com/mailman/listinfo/quattro
> ---
> Watch this space for ads :)
>
```