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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 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 [Leonard Spencer] Churchill (1874 - 1965) Dost thou not know, my son, with how little wisdom the world is governed? -Count Oxenstierna (ca 1620)

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http://www.thaler.com/thcpdf/vre4100.pdf ref is .025%-.05% error with good temp compensation. --- Vic Fraenckel <> 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 > 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 [Leonard Spencer] Churchill (1874 - 1965) > > Dost thou not know, my son, with how little wisdom the world is governed? > -Count Oxenstierna (ca 1620) > > > > ------------------------ Yahoo! Groups Sponsor ---------------------~--> > 4 DVDs Free +s&p Join Now > http://us.click.yahoo.com/pt6YBB/NXiEAA/MVfIAA/dN_tlB/TM > ---------------------------------------------------------------------~-> > > > > > > __________________________________________________

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Vic, I believe Analog and TI makes 5 volt and 2.5 volt precision voltage references. I think they also make much better voltage regulators than the 7805 type. Might help with the source voltage stability. And a bypass cap. very close to the input source to the chip might help. Mark --- Vic Fraenckel <> 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 > > 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 [Leonard Spencer] Churchill (1874 - 1965) > > Dost thou not know, my son, with how little wisdom > the world is governed? > -Count Oxenstierna (ca 1620) __________________________________________________

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Vic, I don't know how you are measuring the "DC" but in many cases where I have seen the ADXL202 used the output is "low pass filtered" and run through an "op amp" to create gain (voltage range). Someone with some more EE experience might be able to suggest the appropriate, opamp, caps and resistors. Good luck, Mark --- Vic Fraenckel <> 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 > > 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 [Leonard Spencer] Churchill (1874 - 1965) > > Dost thou not know, my son, with how little wisdom > the world is governed? > -Count Oxenstierna (ca 1620) __________________________________________________

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--- In basicx@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. Vic, I was surprised by your comment so I looked over the spec. sheet again. Unless A.D. is lying completely, the normal outputs are not sensitive to variations over the specified supply range of 4.75 to 5.25 volts. You should have no trouble finding a 5V regulated supply IC in this range. A high-precision supply won't hurt, of course, but I don't see why it is necessary assuming you are using a micro to measure the duty cycle. If you are integrating the output to turn the waveform into DC or are using the Filt outputs, then of course the output is directly proportional to the supply voltage. What sort of accuracy are you looking for and what are you seeing? There are tricks for getting a more accurate measurement when using the digital outputs. Stan

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Stan, | | What sort of accuracy are you looking for and what are you seeing? | There are tricks for getting a more accurate measurement when using | the digital outputs. | I am measuring the periods of the waveforms. I am trying to use the ADXL as a two axis tiltmeter and have been having a real problem getting repeatability of the tilt measurements. I integrate both periods for each measurement by taking 10 readings of each on each axis and averaging and am not getting the repeatability I had hoped for. I am providing 5 volts from a gel cell and a 7805 regulator. What tricks can I use to get more accurate measurements? Any enlightenment will be appreciated TIA Vic ________________________________________________________ Victor Fraenckel - The Windman 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 [Leonard Spencer] Churchill (1874 - 1965) Dost thou not know, my son, with how little wisdom the world is governed? -Count Oxenstierna (ca 1620)

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Here's one way to use SOICs. This guy soldered the part to a DIP socket and used that in another socket; you could just as well use a header. Small soldering, of course, and one could do a better job, but it's functional. http://mmyotte.free.fr/0726_001.jpg Tom Becker --... ...-- GTBecker@RighTime_com www.RighTime.com The RighTime Clock Company, Inc., Cape Coral, Florida USA

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I was told that the accuracy of the ADC can be significantly influenced if you have any loads on any of the digital input output pins. Is it possible that you are doing something with the I/O pins that is hampering your results?

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> ... I am measuring the periods of the waveforms... Maybe correctly. Have you looked at the signal? Is it noisy? Tom Becker --... ...-- GTBecker@RighTime_com www.RighTime.com The RighTime Clock Company, Inc., Cape Coral, Florida USA

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I have multiple ADXLs. 202s and 210s chips mounted on a custom designed boards. According to the data sheets you need a very clean and stable power supply. I use a dedicated 5v regulator and also current regulators on mine. My power is decoupled with caps since it shares the main power supply with other digital devices....so are the ADXLs according to the datasheets. If powered from the same supply as other digital equipment, the decoupling is REQUIRED per the specs. A/D suggests ferrite beads for some decoupling junctions to ensure the ADXL signals. Also, there is special ground plane and noise specs to isolate the module from the rest of the system along with calibration routines once the module is in place and throughout the life cycle of the module since readings can even be effected as the chip itself changes temperature. The specs recommend calibration at power up and again after temperature changes. All these are just about required to ensure reliability.... according to the specs. My hardware is built according to the datasheets and my BX logic is modeled after the BX Application Note in the BX folder. It sounds to me like you need to clean up that power some more. Hope this helps! .db. -----Original Message----- From: Vic Fraenckel [mailto:] Sent: Monday, September 02, 2002 5:06 AM To: ; Subject: [BasicX] Re: Precision power supply Stan, | | What sort of accuracy are you looking for and what are you seeing? | There are tricks for getting a more accurate measurement when using | the digital outputs. | I am measuring the periods of the waveforms. I am trying to use the ADXL as a two axis tiltmeter and have been having a real problem getting repeatability of the tilt measurements. I integrate both periods for each measurement by taking 10 readings of each on each axis and averaging and am not getting the repeatability I had hoped for. I am providing 5 volts from a gel cell and a 7805 regulator. What tricks can I use to get more accurate measurements? Any enlightenment will be appreciated TIA Vic ________________________________________________________ Victor Fraenckel - The Windman 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 [Leonard Spencer] Churchill (1874 - 1965) Dost thou not know, my son, with how little wisdom the world is governed? -Count Oxenstierna (ca 1620) Yahoo! Groups Sponsor ADVERTISEMENT Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]

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> ... I am measuring the periods of the waveforms... > >Maybe correctly. Have you looked at the signal? Is it noisy? Tom, I have a 60MHz Tec 453 and I have monitored the output wave forms from both channels and both appear quite stable with no discernable jitter or noisiness. Vic ________________________________________________________ Victor Fraenckel - The Windman 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 [Leonard Spencer] Churchill (1874 - 1965) Dost thou not know, my son, with how little wisdom the world is governed? -Count Oxenstierna (ca 1620)

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