improving on the MAX1270 12bit 8ch adc

ErikdS

Hi folks,

I'm in need of a bit more resolution than the MAX1270 12bit ADC can provide, i.e. I need 14 or 16bits. I do need a component that is DIP though, as I have NO equipment whatsoever to tackle any other type of packaging.

Furthermore I'm not lazy but I'm sooo dumb , I'd like the ADC to use SPI as this is something I've worked with before (I'd hate to reinvent the wheel on every new project).

Does anybody have any suggestions?

Most grateful,

Erik

Paul Baker

AD7715 16bit SPI 16-DIP 500 sps $11.08
MAX110 14bit 2 channel differential SPI 48sps 16-DIP $12.72

Prices are from digikey, there are others but more expensive, none have more than two channels, you'll need to use an analog multiplexer to gain more channels. Difficults can arise from using high precision ADCs unless used on a properly designed PCB.

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·1+1=10

ErikdS

Thx, that's great.

What kind of difficulties are you referring to?

Kind regards,

Erik

Jon Williams

Noise.... and unless you design your PCB properly, all the precision you paid for gets wiped out. A electronics rep recently told me that for most apps, 12 bits is practical and anything else is just "marketing."

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Jon Williams
Applications Engineer, Parallax

ErikdS

Thank you Jon,

There's an article on the site named something like 'how to get the most out of your 12bit ADC'. This includes some extra noise reduction circuitry, and features an 8 channel 12bit ADC.

Maybe it's possible to feed my sensor's output to two different channels, once in the raw state (just to estimate how noisy the environment is), and once after it passed through noise reduction and hf-cutoff, what do you think?

If proper use of a 16bit is really that hard, I may settle for 12bit, even if that implies throwing away sensor resolution (half of something still being better than all of nothing).

Erik

tperkins

"A electronics rep recently told me that for most apps, 12 bits is practical and anything else is just "marketing.""

And just to get the counterpoint up, the controls company I work for has at least three each of metrology and process control applications in production/constant use where RDT's or tc's are being used for repeatable measurements in the handsful of mK, like 10 to 5 mK. The low range 4 wire RTD input for the 2704 can repeatably, accurately resolve 3nV in industrial conditions (and in lab use, it has done quite better).

With the setup one customer is putting together, a 2704 two loop controller will maintain a hot and a cold sink to low mK accuracy, and his patent pending, system, has a serious shot at controlling the center zone to low uK accuracy.

There are time 24bits doesn't look like enough.

Yours, Tom Perkins,
molon labe
montani semper liberi
para fides paternae patria

Jon Williams

I don't disagree at all -- the point I was trying to make is that those bits don't come free; circuit and PCB designs have huge impact on final actual resolution of an ADC.

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Jon Williams
Applications Engineer, Parallax

tperkins

Hello Jon,

I wasn't posting to disagree, it's just that I don't know what he's trying to do. He may well need the 16th bit. I suspect he can get the advice on this baord to get there.

And as far as costs go, to get 3nV resolution, you have a long filter time--it's a delta-sigma converter. Scan time for the instrument is, hold on to your hat, 9Hz. Of course that's fine for most temp control apps.

Which reminds me, I need on general principles to search the delta and sigma keywords here and see what pops up.

Yours, Tom P., ml, msl, & pfpp