<?xml version="1.0" encoding="UTF-8" ?>
<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>signal multiplexing problem with A/D converter</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/20200/signal-multiplexing-problem-with-a-d-converter</link><description> Hi, 
I am using 8-channel 4051 multiplexer ,the o/p of this is connected to CS5532 (24 bit sigma delta A/D converter). 
when only a single channel is selected and converted by the adc it works properly . 
 
when more than 1 channel is selected(sequentially</description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/138240?ContentTypeID=1</link><pubDate>Fri, 25 Aug 2006 16:46:05 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:34865466-fe2a-4566-aca3-4ca24240a89a</guid><dc:creator>erik  malund</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;if you could guide on how about going with it. I am using a
1mv/V tedea huntleigh loadcell with a total capacity of 600gms and
looking to measure 10mg. ie a total of 60K external counts.&lt;/i&gt;&lt;br /&gt;
that is 16 bits of precision, it IS achievable, the cheapest
industrial scale I know of that is that precise cost about $8000 and
the manual states &amp;quot;calibrate before each weighing&amp;quot;.&lt;/p&gt;

&lt;p&gt;
To get to 16 bits will probably require a 6 or 8 layer board, an
autocalibration wiight and circuit. a thermal chanber for some of the
components, 4 to 7 ultra stable power supplies, a lot of isolation
between analog and digital .....&lt;/p&gt;

&lt;p&gt;
as I said in an earlier post&lt;br /&gt;
PPS: if you have any hope of getting above 12 bits (again precision,
not resolution) with &amp;#39;economy&amp;#39; (no 4 layer board etc) I am sorry, but
I have to crush that hope.&lt;/p&gt;

&lt;p&gt;
Erik&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/130067?ContentTypeID=1</link><pubDate>Fri, 25 Aug 2006 12:54:02 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:30b06827-4db9-48ad-94ab-55addb8567ef</guid><dc:creator>Singh JS</dc:creator><description>&lt;p&gt;&lt;p&gt;
Eric, I am new to development using the CS5532 for a weighing
scales and would be greatful if you could guide on how about going
with it. I am using a 1mv/V tedea huntleigh loadcell with a total
capacity of 600gms and looking to measure 10mg. ie a total of 60K
external counts.&lt;/p&gt;

&lt;p&gt;
thnks&lt;br /&gt;
Singh&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/123339?ContentTypeID=1</link><pubDate>Fri, 21 Jul 2006 10:30:26 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:5cf9e05f-12e6-4726-8639-7d0e47482d71</guid><dc:creator>erik  malund</dc:creator><description>&lt;p&gt;&lt;i&gt;As for the precision /resolution part , i don&amp;#39;t think it will be a problem for the present application as i am already able to get a stable count for the single channel&lt;/i&gt;&lt;br /&gt;
if the stable count is off, where is the precision&lt;br /&gt;
&lt;br /&gt;
&lt;i&gt;could you please explain (with an example if possible), the difference between precision and resolution.Thanks.&lt;/i&gt;&lt;br /&gt;
Ok, to make it easy we make scale that is full scale at 65.536 kg.&lt;br /&gt;
&lt;br /&gt;
You put a weight of 30,270 kg on the scale and get a count of 30127, when you put a weight of 30.271 kg on the scale you get a count of 30128.&lt;br /&gt;
&lt;br /&gt;
The difference between 30,127 and 30,128 is the resolution (1g), the difference between 30.270 and 30.127 (143g) is the precision (error)&lt;br /&gt;
&lt;br /&gt;
the resolution is &amp;#39;automatic&amp;#39; the precision is a ***.&lt;br /&gt;
&lt;br /&gt;
A scale that is precise to 5 decimal digits will cost you a minimum of $10.000 a scale with a resolution of 6 decimal digits can be had for $100&lt;br /&gt;
&lt;br /&gt;
Erik&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/112231?ContentTypeID=1</link><pubDate>Fri, 21 Jul 2006 09:52:00 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:0494ebbe-40c5-43dd-a2a5-c2ed0ea9aeab</guid><dc:creator>sujit nair</dc:creator><description>&lt;p&gt;Thanks for the replies.&lt;br /&gt;
&lt;br /&gt;
&lt;i&gt;&lt;br /&gt;
So if you were only sampling a single channel, signal changes in the other three channels had no effect on the one channel you were sampling ?&lt;/i&gt;&lt;br /&gt;
&lt;br /&gt;
Yes.That&amp;#39;s right.  When i was sampling only a single channel fixing the multiplexer inputs for a particular channel, there was no effect of the other channels on the sampled channel.&lt;br /&gt;
&lt;br /&gt;
I will check out the ADuC8xx series suggested by you.&lt;br /&gt;
Although , it will be really helpfull (and time saver) , if i am able to find any suitable front-end multiplexer for the present configuration replacing the 4051.&lt;br /&gt;
&lt;br /&gt;
The reason why i am using(reluctant to change) the CS5532 is that i have worked with the chip previously also and have already written the spi interface and the register configration part.&lt;br /&gt;
&lt;br /&gt;
I googled extensively , but was not able to find any example / application note showing the chip used in externally multiplexed configuration.&lt;br /&gt;
&lt;br /&gt;
&lt;i&gt;SILabs has what you want inside the micro&lt;/i&gt;&lt;br /&gt;
I am presently using the atmel AT89S52 microcontroller.I am not sure what all changes i will have to make to accomodate for the microcontroller change.that seems a little difficult to me.&lt;br /&gt;
&lt;br /&gt;
As for the precision /resolution part , i don&amp;#39;t think it will be a problem for the present application as i am already able to get a stable count for the single channel.(all are identical channels.The Sampling rate may cause / introduce problems though when i start switching channels)&lt;br /&gt;
&lt;br /&gt;
Thanks again for your replies.&lt;br /&gt;
I will try out the ideas/suggestions/links and post any progress i am able to make on this.&lt;br /&gt;
&lt;br /&gt;
PS:&lt;br /&gt;
Erik,&lt;br /&gt;
i am really a newbie to this.&lt;br /&gt;
could you please explain (with an example if possible) , the difference between precision and resolution.Thanks.&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/98290?ContentTypeID=1</link><pubDate>Fri, 21 Jul 2006 09:06:37 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:371731c9-8c31-4e63-9073-bf50e51c2e36</guid><dc:creator>erik  malund</dc:creator><description>&lt;p&gt;&lt;i&gt;Can you suggest any other A/D converter which can be used in this application(with internal mux or with compatible external mux).  a 16-bit ADC might also be sufficent.&lt;/i&gt;&lt;br /&gt;
SILabs has what you want &lt;b&gt;inside the micro&lt;/b&gt; &lt;a href="http://www.silabs.com/tgwWebApp/appmanager/tgw/tgwHome?_nfpb=true&amp;amp;_pageLabel=interactiveGuide&amp;amp;col=adc1" target="_blank"&gt;http://www.silabs.com/tgwWebApp/appmanager/tgw/tgwHome?_nfpb=true&amp;amp;_pageLabel=interactiveGuide&amp;amp;col=adc1&lt;/a&gt; There are other &amp;#39;51s as well with mux&amp;#39;ed A/D built in check Keil device database &lt;a href="http://www.keil.com/dd/parm_search.asp"&gt;http://www.keil.com/dd/parm_search.asp&lt;/a&gt;&lt;br /&gt;
&lt;br /&gt;
For external A/D and multiplexers, check e.g. Maxim, Analog Devices, Linear Technology.&lt;br /&gt;
&lt;br /&gt;
Erik&lt;br /&gt;
&lt;br /&gt;
PS, If you are new at this, be ready for some real work.  If you, with the best first 4 or 6 layer layout you can do, get to 11 bits of &lt;b&gt;precision&lt;/b&gt; (not resolution) within one week consider yourself extremely lucky.  When I did weigh scales the engineer that did nothing but analog front ends for 10+ years considered himself lucky when reaching 15 bits in the high priced models.&lt;br /&gt;
&lt;br /&gt;
PPS: if you have any hope of getting above 12 bits (again &lt;b&gt;precision&lt;/b&gt;, not resolution) with &amp;#39;economy&amp;#39; (no 4 layer board etc) I am sorry, but I have to crush that hope.&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/98288?ContentTypeID=1</link><pubDate>Fri, 21 Jul 2006 09:02:58 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:cbd5ecfd-615d-4397-aeed-ac437f4dc96a</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;i&gt;I  had till this point tested the complete application for a single channel and it worked perfectly but the multiplexing part didn&amp;#39;t work.&lt;/i&gt;&lt;br /&gt;
&lt;br /&gt;
So if you were only sampling a single channel, signal changes in the other three channels had no effect on the one channel you were sampling ?&lt;br /&gt;
&lt;br /&gt;
&lt;i&gt;Can you suggest any other A/D converter which can be used in this application(with internal mux or with compatible external mux).&lt;br /&gt;
a 16-bit ADC might also be sufficent.&lt;/i&gt;&lt;br /&gt;
&lt;br /&gt;
Have a look at Analog Devices&amp;#39; ADuC8xx series.&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/74211?ContentTypeID=1</link><pubDate>Fri, 21 Jul 2006 08:36:19 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:709d5758-a0a1-454a-b3bb-2587f9e053ea</guid><dc:creator>sujit nair</dc:creator><description>&lt;p&gt;OK. So the Hardware is wrong. Thanks for solving part of my problem.&lt;br /&gt;
&lt;br /&gt;
But can you please suggest an alternative design or A/D converter.&lt;br /&gt;
Here&amp;#39;s what my problem is.&lt;br /&gt;
&lt;br /&gt;
I need to sample 4 analog channels sequentially&lt;br /&gt;
(ch1-ch2-ch3-ch4-ch1-ch2...) all of which are weigh scale signals and based on this i need to do some set-point based output control.(channels and thier control are independent of each other)&lt;br /&gt;
&lt;br /&gt;
I had till this point tested the complete application for a single channel and it worked perfectly but the multiplexing part didn&amp;#39;t work.&lt;br /&gt;
&lt;br /&gt;
I Know there is a 4 channel A/D conerter from the same family(CS5534), but i was not able to get it out there.&lt;br /&gt;
&lt;br /&gt;
Can you suggest any other A/D converter which can be used in this application(with internal mux or with compatible external mux).&lt;br /&gt;
a 16-bit ADC might also be sufficent.&lt;br /&gt;
&lt;br /&gt;
thanks,&lt;br /&gt;
sujit&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: signal multiplexing problem with A/D converter</title><link>https://community.arm.com/thread/46449?ContentTypeID=1</link><pubDate>Thu, 20 Jul 2006 07:21:40 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:25c83e7b-d50d-49d5-a91f-7c10fffa7454</guid><dc:creator>erik  malund</dc:creator><description>&lt;p&gt;&lt;i&gt;4051 multiplexer,the o/p of this is connected to CS5532(24 bit&lt;/i&gt;&lt;br /&gt;
this makes absolutotally no sense, you are using an extremely imprecise  multiplexer in front of a 24 bit A.D???&lt;br /&gt;
&lt;br /&gt;
Do you even have an inkling of understanding what you are doing?&lt;br /&gt;
&lt;br /&gt;
Erik&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>