Re: E-Meter autoscan

["David G Leatham" <res0inod@verizon.net>]

Xantrax ( they live near me ) strikes again.  Thanks Lee - you gave values
and spelling to how to make somthing work that was from a past life -- maybe
the ref book (again marine )  -- Yes : The 12 volt Doctor's Practical
Handbook.  Useful reference anyday.
----- Original Message -----
From: "Lee Hart" <leeahart@earthlink.net>
To: <ev@listproc.sjsu.edu>
Sent: Tuesday, April 30, 2002 12:19 PM
Subject: Re: E-Meter autoscan


> David G Leatham wrote:
> > If you are refering to the (was Cruising Equipment) Link 10...
>
> Yes, that's it. The Cruising Equipment E-meter and the Heart Interface
> Link 10 are one and the same.

Now Xantrax.  I believe Heart Interface and Cruising merged or were both
assumed by ITT a score of years back.  Trace inv's and Statpower lately have
all come under the same wing or something close.  So to me as a NW USA guy
using NW products from nearby competitors --BOY what a change...we had heard
that Heart and Trace were tring to... but had too many law suits
interefearing.

Enough gossip  I read from the list about many other E suppliers  I'm not
familiar with.

Sorry about THE David G Leatham Thing.  The G is for George  But David, dave
or dl suits me well.

dl
>
> > could add another E-Meter or just another meter so that the E-Meter
> > would not have to autoscan.  I wonder if a simple resistor and a
> > zener diode could be used to make an expanded scale analog meter
> > suitable for those high volt EV's using a millamp meter and redoing
> > the numbers by hand, using the E-Meter as reference to calibrate the
> > handbuild.
>
> Yes, that works exactly as described. An expanded-scale voltmeter is a
> milliammeter, resistor, and zener diode, all in series.
>
> All by itself, the milliammeter would be something like 0 to 0.1v full
> scale. The series resistor scales this up. For example, a 0 to 1ma meter
> is 1/1ma = 1/0.001amp = 1000 ohms per volt. So a 0 to 100 volt scale
> takes a 100v x 1000 ohms/volt = 100,000 ohm (100k) series resistor. To
> be strictly correct, this is the total resistance including the
> resistance of the meter itself. Use a small potentiometer in series and
> you can calibrate it.
>
> A zener diode in series subtracts its zener voltage from all readings. A
> 50 volt zener in series with the above 0-100v meter makes it a 50-150v
> meter. Note that zener diodes are far from ideal at low currents; the
> actual zener voltage will deviate substantially from the "rated" zener
> voltage. You will probably have to hand-calibrate the scale.
>
> If the meter you use is very low current full scale, like 50 microamps,
> then the resistor value gets very large, and you may have trouble with
> leakage currents. Fingerprints, dirt, or moisture on the surface of the
> zener or resistor will affect the readings. If the zener is in a glass
> case, then light shining on it will affect the reading.
>
> > a battery monitor that used an inductive pickup for amps.
>
> Inductive pickups are used for measuring AC current, but don't work for
> DC. However, there are Hall-effect sensors that measure the magnetic
> field generated by the DC current in a wire. They are generally more
> expensive, and have trouble maintaining accuracy over a large range of
> current.
> --
> Lee A. Hart                Ring the bells that still can ring
> 814 8th Ave. N.            Forget your perfect offering
> Sartell, MN 56377 USA      There is a crack in everything
> leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen
>