Oh yes, the 2 was a typo.
Hmm so you mean that I should build this up with a 12M7 and a 100K +-
10K fixes resistor trim pot combination, write the simpler sampling
routine, and finally correct the 1V linearity error by changing the
divider's ratio with the trim pot?
Jens
threeneurons
Hello,
thanks for the useful tips, I especially like the idea of the copper-
clad board, that could be useful I guess.
Averaging is in fact cool, I am already calculating the average of 50
measurements giving me a data refresh rate of about 3Hz. I always
thought why do these multimeters have
On 14/10/2010, at 08.45, Jens Boos wrote:
Hello,
thanks for the useful tips, I especially like the idea of the copper-
clad board, that could be useful I guess.
CUT
Hi Jens,
Why not go the totally retro way of doing it with an outdated and old DMM chip,
when you are using Nixies anyway
Hi Per,
hmm the CA3162 is an interesting chip, but spontaneously I would
certainly not know where still to obtain it... I checked Ebay, though,
and they are for sale @ 15EUR a piece. My ADCs from Maxim were cheaper
as samples ;-) But I don't get something: You can use the chip for
many input
Oh and I forgot the schematic:
http://www.jb-electronics.de/tmp/voltmeter_schematic.gif
Jens
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Hello Frank,
Or something like this:
mean += WertADC;
and
if (mean_counter = 10) {
Spannung = (mean * 0.3215) / mean_counter) ;
Just to save a bit of time on all those floating point calculations...
That is a good idea indeed, I will change that.
Jens
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On 14/10/2010, at 18.46, Jens Boos wrote:
Hi Per,
hmm the CA3162 is an interesting chip, but spontaneously I would
certainly not know where still to obtain it... I checked Ebay, though,
and they are for sale @ 15EUR a piece. My ADCs from Maxim were cheaper
as samples ;-) But I don't get
Hello Gaston,
Jens,
David gave you sound advice. A voltage regulator fitness for a
given task is not only related to precision. It also has to do among
other things with repeatability (its ability to reach a voltage every
time it is started),
Yes, but I have measured the voltage several
Oh, and to clean up the noise a little more, is to narrow the
bandwidth. You can drop a small cap across the lower resistor of your
divider. In addition to that, if you have some left over RAM, you can
make a rolling queue of samples. Then take the average value of those
samples and display the
Hello,
oh I just realised that there was in fact a bit shifting error in the
readADC() routine. Embarassing. I did not see it the whole day. OK
now the data is correctly transferred into the PIC, next thing to
check will be the multiplication (because the values are still off by
about 20V). Or
And another follow-up: I realised my offset was in fact a linearity
error, so I tweaked a little bit, and a correcting term of 0.004 / Bit
did the trick. Is this ethical? ;-)
Jens
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