Recommendations for 24 bit ADC that can work with BS2

bookworm1706

Hello everyone,

After going through many ADC's trial and error, I was wondering if anyone could reccommend a 24 bit ADC or at least a 16 bit that is garanteed to work with the BS2 SPI protocol (SHIFTIN SHIFTOUT), I can get the LTC1286 examples working but they do not have enough bits for the resolution I need. I have tried other companies but I cannot get their SPI to sync correctly with the BS2s. I am not sure if it is because of my lack of knowledge, but if I can get a chip that I know will work then I can most likely figure it out.

Thanks

schneidera

Hi

I think the last thing you probably need is a 24bit (or even a 16bit one) ADC, this is why:
Assuming you convert 5V at a resolution of 24bit, one bit equals a voltage of 5V/(2^24), which is roughly 300nV (nanovolt). Assuming you have 30uV of noise -- no to bad a value -- two orders of magnitudes the 1bit voltage, it would result in roughly wasting 6 to 7 bits (2^7=128) of pure noise.
Assuming 300uV of noise (three orders of magnitude the 1bit voltage) you would even lose 9 to 10 bits (2^10=1024). While 24bit ADCs are available today, it is quite a challenge to correctly design a circuit using one.

Probably the only thing you need is to compute your ADC values to match the required range. But you have to be more specific about your application's requirements.

See you
Adrian

bookworm1706

Hello Adrian, Thankyou for your reply!

Thank you for talking to me. Your math makes a lot of sense. I was looking for a 24 bit adc because that is what a guy at the company I bought the sensor from reccomended to achieve a resolution of at least 0.005 deg in order to measure a thousandths of an inch change in height over a one foot span.It is the SCA103 made by VTI Tech inclinometer. This supposedly can achieve 0.001 deg with a 0 to 1 deg range. and a 10 Hz Bandwidth with the setup the guy reccomended. The inclinometer actually has an onboard ADC, however, using it limits the resolution to 0.009 degrees. Anyhow, since I posted this I have already bought a Propeller chip and I have been trying to learn how to use it. It is almost easier then the stamp but its language being dependent on white space has taken some getting used too, Butit is a lot more flexible then the stamp. There is also an object already written for interfacing with a different 24bit ADC that I have outputting numbers now. I am now trying to see if I am getting close to what I am supposed to be getting. Thanks again for your time

Jonathan