HMC1052 range and consistency control?

I have installed a number of these compasses on identical boards, and
I've found that not only do their measurements differ, but also even
the range of values.

at the same position and direction, they give significantly different
values for +/-.  This is a slight annoyance having over 50 boards to
go in the firmware and adjust the offsets before calculating the
direction, but is this a common thing?

Lastly and more worrying is the difference in ranges that the values
give when i read from them in all 360 degrees with maybe 16
increments.  For example, one compass may give a maximum value for +
of say 2 volts and a minimum of 1 volt, with the same for the -.
Another may give a range for + of 1.5 volts to 1.7 volts, and the -
may give 1 volt to 2 volts.  And another will have .8 volts to 2.5
volts for + and 1.1 to 1.15 volts for -.  Are these common issues?
they are all implemented on identical boards.

Johnny Chang wrote:

> Lastly and more worrying is the difference in ranges that the values
> give when i read from them in all 360 degrees with maybe 16
> increments.  For example, one compass may give a maximum value for +
> of say 2 volts and a minimum of 1 volt, with the same for the -.
> Another may give a range for + of 1.5 volts to 1.7 volts, and the -
> may give 1 volt to 2 volts.  And another will have .8 volts to 2.5
> volts for + and 1.1 to 1.15 volts for -.  Are these common issues?
> they are all implemented on identical boards.

Did you use the flip coils to reset the offsets? How did you measure it?
They don't output volts, it is a resistor bridge. Maybe your amplifier
circuit has some offset or different gain? Can you measure the resistors of
different parts before soldering (and after applying a pulse to the flip
coils)?

-- 
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de

Johnny Chang wrote:
> 
> I have installed a number of these compasses on identical boards,
> and I've found that not only do their measurements differ, but
> also even the range of values.
...

We obviously have a considerably different idea of the meaning of
'compass'.  To me, this is an item containing a magnet and pivot,
that self adjusts to point (more or less) at magnetic north.

So what are you talking about?

-- 
 [mail]: Chuck F (cbfalconer at maineline dot net) 
 [page]: <http://cbfalconer.home.att.net>
            Try the download section.

On Jul 14, 4:19=A0pm, Frank Buss <f...@frank-buss.de> wrote:
> Johnny Chang wrote:
> > Lastly and more worrying is the difference in ranges that the values
> > give when i read from them in all 360 degrees with maybe 16
> > increments. =A0For example, one compass may give a maximum value for +
> > of say 2 volts and a minimum of 1 volt, with the same for the -.
> > Another may give a range for + of 1.5 volts to 1.7 volts, and the -
> > may give 1 volt to 2 volts. =A0And another will have .8 volts to 2.5
> > volts for + and 1.1 to 1.15 volts for -. =A0Are these common issues?
> > they are all implemented on identical boards.
>
> Did you use the flip coils to reset the offsets? How did you measure it?
> They don't output volts, it is a resistor bridge. Maybe your amplifier
> circuit has some offset or different gain? Can you measure the resistors =
of
> different parts before soldering (and after applying a pulse to the flip
> coils)?
>
> --
> Frank Buss, f...@frank-buss.dehttp://www.frank-buss.de,http://www.it4-sys=
tems.de

Er whoops, instead of + and -, i meant bridge1 +/- difference and
bridge2 +/- difference.  We use the same amplification circuit for
each one, but I can test them and measure them whenever I get back to
lab.  Yeah, we send a pulse to set/reset.