Precision power supply
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I read an interesting post on one of these maillists concerning the accuracy
of the ADXL202 measurements being effected by the stability of the voltage
supplied to the IC. This got me to thinking that this might be the reason
for my dissatisfaction with the accuracy I was experiening when using the
'202.
How can I control the stability of the 5 volt source supplying the IC so as
to increase the accuracy of the measurements of my ADXL?
Any enlightenment will be appreciated.
TIA
Vic
________________________________________________________
Victor Fraenckel - The Windman vfraenc1@n...
KC2GUI www.windsway.com
Home of the WindReader Electronic Theodolite
Read the WIND
"Victory at all costs, victory in spite of all terror, victory however long
and hard the road may be; for without victory there is no survival."
- Winston [noparse][[/noparse]Leonard Spencer] Churchill (1874 - 1965)
Dost thou not know, my son, with how little wisdom the world is governed?
-Count Oxenstierna (ca 1620)
of the ADXL202 measurements being effected by the stability of the voltage
supplied to the IC. This got me to thinking that this might be the reason
for my dissatisfaction with the accuracy I was experiening when using the
'202.
How can I control the stability of the 5 volt source supplying the IC so as
to increase the accuracy of the measurements of my ADXL?
Any enlightenment will be appreciated.
TIA
Vic
________________________________________________________
Victor Fraenckel - The Windman vfraenc1@n...
KC2GUI www.windsway.com
Home of the WindReader Electronic Theodolite
Read the WIND
"Victory at all costs, victory in spite of all terror, victory however long
and hard the road may be; for without victory there is no survival."
- Winston [noparse][[/noparse]Leonard Spencer] Churchill (1874 - 1965)
Dost thou not know, my son, with how little wisdom the world is governed?
-Count Oxenstierna (ca 1620)
Comments
I would use a variable voltage regulator controled by an opto isolator
with a pot on the led side to fine tune it. Oh and some good caps to
filter with!
Just my $0.02
Wayne
--- In basicstamps@y..., "Vic Fraenckel" <vfraenc1@n...> wrote:
> I read an interesting post on one of these maillists concerning the
accuracy
> of the ADXL202 measurements being effected by the stability of the
voltage
> supplied to the IC. This got me to thinking that this might be the
reason
> for my dissatisfaction with the accuracy I was experiening when
using the
> '202.
>
> How can I control the stability of the 5 volt source supplying the
IC so as
> to increase the accuracy of the measurements of my ADXL?
>
> Any enlightenment will be appreciated.
>
> TIA
>
> Vic
> ________________________________________________________
>
> Victor Fraenckel - The Windman vfraenc1@n...
> KC2GUI
www.windsway.com
>
> Home of the WindReader Electronic Theodolite
> Read the WIND
>
> "Victory at all costs, victory in spite of all terror, victory
however long
> and hard the road may be; for without victory there is no survival."
> - Winston [noparse][[/noparse]Leonard Spencer] Churchill (1874 - 1965)
>
> Dost thou not know, my son, with how little wisdom the world is
governed?
> -Count Oxenstierna (ca 1620)
>How can I control the stability of the 5 volt source supplying the IC so as
>to increase the accuracy of the measurements of my ADXL?
Use a better regulator <grin>. For example, the LP2950AC from National
Semiconductor has a 0.5% (worst case) initial accuracy at 25C and holds
that within 20 ppm/C typical (100 ppm/C worst case) over its operating
temperature range of -40 thru +125C. The ADXL has a far worse temperature
coefficient than this - its error will dominate.
Do note that the LP2950 is classed as a low drop-out regulator and
*requires* a large value output capacitor to ensure stability. I generally
use a 22 uF 10V tantalum because of the temperature range that most of my
products operate at but a 22 uF aluminum electrolytic works just fine over
the consumer temperature range (room temperature). Do NOT use a large
value ceramic cap as the output filter - the regulator *will* oscillate!
dwayne
--
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 18 years of Engineering Innovation (1984 - 2002)
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> From: "Vic Fraenckel" <vfraenc1@n...>
> Subject: Precision power supply
>
> How can I control the stability of the 5 volt source supplying the IC so
as
> to increase the accuracy of the measurements of my ADXL?
I use the LP2950ACZ-5.0 micropower voltage regulator with the ADXL202.
100 ma, low quiescent current, low dropout, 20 ppm/C deg stability.
http://www.national.com/ds/LP/LP2950.pdf
Hope this helps,
Dave
Infiltec
http://www.infiltec.com/
Another possible error source is variable zero g stability with
temperature. The Analog Devices website has an applications note about
different strategies for temperature compensation, including mounting a
power resistor on top of a 105 to ovenize it.
Temperature compensation appears most relevant to applications with
wider variations of temperature, such as RC aircraft or a fuel dragster.
But since you work with wind, your applications might require it.
Dennis
Original Message
From: Vic Fraenckel [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Eh_Cs5YeReyQlmCJNefcOCrseotV6VZ2KWjrr6WtBEC86Isft7hxTupEQrDwr32GXpKivOTZmaPJlCo]vfraenc1@n...[/url
Sent: Saturday, August 31, 2002 5:20 AM
To: BasicX Maillist; BasicStamps
Subject: [noparse][[/noparse]basicstamps] Precision power supply
I read an interesting post on one of these maillists concerning the
accuracy of the ADXL202 measurements being effected by the stability of
the voltage supplied to the IC. This got me to thinking that this might
be the reason for my dissatisfaction with the accuracy I was experiening
when using the '202.
How can I control the stability of the 5 volt source supplying the IC so
as to increase the accuracy of the measurements of my ADXL?
Any enlightenment will be appreciated.
TIA
Vic
________________________________________________________
Victor Fraenckel - The Windman vfraenc1@n...
KC2GUI
www.windsway.com
Home of the WindReader Electronic Theodolite
Read the WIND
"Victory at all costs, victory in spite of all terror, victory however
long and hard the road may be; for without victory there is no
survival."
- Winston [noparse][[/noparse]Leonard Spencer] Churchill (1874 - 1965)
Dost thou not know, my son, with how little wisdom the world is
governed? -Count Oxenstierna (ca 1620)