--- In , Chad Russel <chadrussel@y...> wrote: > Same problem here. So what I did with moving average was to subtract > min from max of buffer. If less than certain value, then stable. > > Chad One simple way to get rid of some of the noise is to delete the min max readings. since it seems you are talking about a 16 bit value, and if you want to stay in 16 bit numbers, another way is to take the average you had and then find out how much your current reading is different. This is averaging the deviation. Then just adding it back to the average to get a new average. This method stops working when you have really noisy signals in the upper end of the range. ie: 4.8 volts or so. To handle that, you can just subtract some value from everything and then add it back in the final stages. Dave

If you are havin problems with code here is some to get you started. I find this method simple and sufficiently accurate for most programs. This routine works by reading the A/D signal 256 times adding the result each time to a running total. With an 8 bit reading you will have a 16 bit result after 256 readings. The most sig. 8 bits of this result is the average input. With this method there is no maths involved apart from a simple addition. If you are using a 10 bit A/D the same method can be used with some mods. If you want you can drop the least sig 2 bits of the 10 bit reading and use the same routine! It depends on the number of quantizing steps you require. You will need 4 working regs count - used to count 256 loops. result - holds your A/D reading (not really necessary you can read it from your A/D reg.) reshi - stores the most significant 8 bits of averaged signal. reslo - stores the least sig 8 bits of averaged signal. clrf count ; first DECFSZ instruction will cause ; this reg to go from 00h to 0FFh Loop call (Your A/D read routine) ; get the reading, store it ; in the reg called result ; in your A/D routine movf result,W ; Copy the reading to W reg addwf reslo,F ; Add it to the LSB reg btfsc STATUS,C ; if overflow occurs inc MSB reg incf reshi,F decfsz count,F ; do it 256 times to get average goto Loop movf reshi,W ; (256 readings)/256 in reshi You're averaged 8 bit reading is now in the reshi reg. Hope this helps. --- In , "burt0072003" <burt007@i...> wrote: > Thank you all for your kind help, this gives me some idea for the > above problem, but when it comes to coding in assembly I am not good. > The problem was, when you have 16 bit resolution, last bits will be > going all over the place because of instability, noise, analoge > voltage not settled etc. so some way of seeing them stable or > changing slowly until it is stabilized. Once stable seeing on lcd a > stable number especially the last digits not changing so much.

I've had decent results by doing a simple filter that uses the previous filtered value in the majority. for example, new = 3/4*current + 1/4*sample current = new by using a power of 2 as the divisor, it makes the math easy. this tends to converge some what slowly so you can't measure fast moving values. It works just fine in temperature measurements. --- In , "martin de lange" <martin_de_lange@x> wrote: > The last one or two bits on the LSB would normally not be used to display. You could dampen the display further by display updating slower or averageing the display updating. The resolution is only 10- 12 bit on the LSB and not the full 16 bit. > > regards > Martin > ----- Original Message ----- > From: burt0072003 > To: > Sent: Thursday, February 26, 2004 3:20 AM > Subject: [piclist] Re: Looking for codes to average adc results > Thank you all for your kind help, this gives me some idea for the > above problem, but when it comes to coding in assembly I am not good. > The problem was, when you have 16 bit resolution, last bits will be > going all over the place because of instability, noise, analoge > voltage not settled etc. so some way of seeing them stable or > changing slowly until it is stabilized. Once stable seeing on lcd a > stable number especially the last digits not changing so much. > > to unsubscribe, go to http://www.yahoogroups.com and follow the instructions > -------------------------------- ---------- > Yahoo! Groups Links > > a.. To

The last one or two bits on the LSB would normally not be used to display. You could dampen the display further by display updating slower or averageing the display updating. The resolution is only 10-12 bit on the LSB and not the full 16 bit.

regards

Martin

----- Original Message -----

From: burt0072003

To: p...@yahoogroups.com

Sent: Thursday, February 26, 2004 3:20 AM

Subject: [piclist] Re: Looking for codes to average adc results

Thank you all for your kind help, this gives me some idea for the above problem, but when it comes to coding in assembly I am not good. The problem was, when you have 16 bit resolution, last bits will be going all over the place because of instability, noise, analoge voltage not settled etc. so some way of seeing them stable or changing slowly until it is stabilized. Once stable seeing on lcd a stable number especially the last digits not changing so much.

to unsubscribe, go to http://www.yahoogroups.com and follow the instructions

Same problem here. So what I did with moving average was to subtract min from max of buffer. If less than certain value, then stable. Chad --- burt0072003 <> wrote: > Thank you all for your kind help, this gives me some idea for the > above problem, but when it comes to coding in assembly I am not good. > > The problem was, when you have 16 bit resolution, last bits will be > going all over the place because of instability, noise, analoge > voltage not settled etc. so some way of seeing them stable or > changing slowly until it is stabilized. Once stable seeing on lcd a > stable number especially the last digits not changing so much. ===== My software has no bugs. Only undocumented features. __________________________________

Thank you all for your kind help, this gives me some idea for the above problem, but when it comes to coding in assembly I am not good. The problem was, when you have 16 bit resolution, last bits will be going all over the place because of instability, noise, analoge voltage not settled etc. so some way of seeing them stable or changing slowly until it is stabilized. Once stable seeing on lcd a stable number especially the last digits not changing so much.

--- Dave MuMuchadadavemuchaujunoom> wrote: > --- In pipiclistayahoogroupsom, "Leon Heller" <leleoneller@h...> > wrote: > > > > ----- Original Message ----- > > From: "Paul James E." <jajamesp...> > > To: <pipiclistayahoogroupsom> > > Cc: <chchadrussel...> > > Sent: Friday, February 20, 2004 6:24 AM > > Subject: Re: [pipiclistRe: Looking for codes to average adadcesults > > > > > > > > > > Sorting and finding the middle number is the median, not the > mean. > > > > The median can sometimes be more 'meaningful' than the mean; it > depends on > > how the data are distributed. It is another type of average. > > > > Leon > Yup, > > If one has a noisy input, all the averaging will not reveal the > correct value and it will be very noisy. > > Taking 20 reading and throwing out the 5 highest and 5 lowest is a > simple method of ignoring the noise. > > OF course as low pass filter will do wonders. > > Dave As with any black box, formula, or algorithm the desired transfer function, range, and domain need to be defined. A square wave at a multiple of the sample rate will give interesting results in any sampling situation, for example. Chad :D ===== My software has no bugs. Only undocumented features. __________________________________

--- In , "Leon Heller" <leon_heller@h...> wrote: > > ----- Original Message ----- > From: "Paul James E." <jamesp@i...> > To: <> > Cc: <chadrussel@y...> > Sent: Friday, February 20, 2004 6:24 AM > Subject: Re: [piclist] Re: Looking for codes to average adc results > > > > Sorting and finding the middle number is the median, not the mean. > > The median can sometimes be more 'meaningful' than the mean; it depends on > how the data are distributed. It is another type of average. > > Leon Yup, If one has a noisy input, all the averaging will not reveal the correct value and it will be very noisy. Taking 20 reading and throwing out the 5 highest and 5 lowest is a simple method of ignoring the noise. OF course as low pass filter will do wonders. Dave

Why do a circular buffer? I just accumulate a sum as the A/D samples come in. I maintain a sum and a count. In several applications, I accumulate 256 samples (just watch for the counter to hit zero!), then divide by 256 by throwing out the 8 lsb of the sum. Harold FCC Rules Online at http://www.hallikainen.com

--- Harold Hallikainen <> wrote: > > Why do a circular buffer? I just accumulate a sum as the A/D samples > come in. I maintain a sum and a count. In several applications, I > accumulate 256 samples (just watch for the counter to hit zero!), > then divide by 256 by throwing out the 8 lsb of the sum. > > Harold > FCC Rules Online at http://www.hallikainen.com The reason for the circular buffer is that you have a new average computed every sample time. Otherwise you have to wait for exactly a power of 2 cycles or divide by some number like 107. Not good for real time stuff. Chad ===== My software has no bugs. Only undocumented features. __________________________________