dear
thank you for your reply
well there is no need for simultaneous update rate for all channels and for input stage i will use buffer amp for each volt/current reading because
for positive 0 to 100 volt reading dc potential can be applied directly to adc input after scaling due common ground but for negative volt 0 to -100 volts i will use inverting buffer amplifier (note i will use split/complementary supply for adc buffer amplifier) all amplifier will be used in four gain setting option using relay/74hc4052 switch for fine volt /current reading here i have one more question from you if i use 74hc4052 for gain selection then what would be the overall impact on required performance
well i had seen data sheet for ads1258 and Table 6. Noise Performance 18.9 noise free bit which is less then 20 bit noise free resolution so how to deal with this ads1256 have good performance i am considering to use ref5025id ic for vref of ads1256 where i can add 47uf capacitive load on ref5025 output can you plz verify the performance in this way on ads1256evm by bypassing buffer amplifier opa211 and using ref5025id with 47uf capacitor on vref output directly connected to ads1256 vref pin so i will be confident about my circuit and what would be long-term drift error in case of this heavy capacitive load on ref5025id out put
well about ads1248 that is economical version so what would be proper circuit for this adc would you recommend this adc for my required performance
at the moment i have these two parts available in my hand ads1256 and ads1248 and for ads1258 i have to wait until i recive ads1258 adc ic
i am curious that you did briefed on ads131 is this not suitable for my application while i need only 4 samples per channels and after internal over sampling only 1k sample/sec is available where i have enough computing resources available in micro-controller to further oversampled 256 times adc result to get more noise free bits
i have also pga117 in my stock(which we already using in data logger products) and according to data sheet ads1259 can provide 16 samples/sec at 21 noise free bit resolution i exactly need scope gain for volt current display and pga117 have scope gains where pga117 will cost 4.8$ +ads1259 will cost 15.74$ and that will be total 20.54 $ and thats more economical but how to fit these two ic's together for 20bit performance now if you help me out to solve this chicken and egg mystery i will be very grateful to you
for current measurement single low side current sense amplifier will be used
for third channel i will use isolation amplifier and in any case if i am not able to get six channel measurement at 20 noise free bits from single adc ic then i will use additional adc for third volt/current channel
regard
Shams Iqbal