Haven't seen the "Just Brits" schematic yet (the link as given doesn't work
for me), but my ammeter circuit (using an Allegro Semiconductor Hall-effect
sensor chip) also requires an outboard amplifier. The one I configured uses
an op-amp, so that gain and offset can be adjusted. However, you must
account for parameter drift due to temperature, and also voltage changes on
the -12-V line in the car.
That's why I chose a MIL-spec op-amp with a -55 degree C to +125 degree C
operational range, and a stiff monolithic voltage regulator chip as well.
Even those ICs don't ensure thermal stability, only IC survival.
That's why I ultimately went with an old fashioned zero-center ammeter.
== Alex in Maine
1960 BT7 "Blue Mainie"
Former owner 1957 100-6, 1967 BJ8
Amateur Radio AI2Q
http://users.adelphia.net/~alexmm/ai2q.htm
.-.-.
-----Original Message-----
From: owner-healeys@autox.team.net
[mailto:owner-healeys@autox.team.net]On Behalf Of Alan F Cross
Sent: Monday, April 19, 2004 1:02 PM
To: BillHUCK@aol.com
Cc: happolk@cox.net; healeys@autox.team.net
Subject: Re: Ammeters
In message <51.3d78e8d8.2db539d2@aol.com>, BillHUCK@aol.com writes
>I have a problem with the concept of automotive ammeters.
>
>Should anything go wrong with the shunt, all power shuts off.
>Is that shunt not just one more link to possible failure? Bill
Huck
>
Been watching this thread with some interest. I too have thought about
adding an ammeter, but don't want to cut into the loom or route the
entire current supply through a small meter with shunt.
But ...
|