DAC ADC Board - Design Help Requested

you forget to tell, how much speeed is? or bandwide?

what mean is 10ppm here with? different field has differnt explain. Im afraid.

Good question.

Our range of voltage is 0-10V and 4uV precision and 10uV accuracy is required. Sampling rate 0.5Hz to 10Hz range.

Hello Shyam, It is not clear to what the 10ppm refers. Do you mean absolute accuracy? I would expect it to refer to temperature drift, 10ppm/degree C for example.

I have done projects that require these types of accuracy but we must be extremely careful about what exactly is required and also how it is to be verified.

Ultimately, we must also know in what type of environment it would need to perform as well as the nature of the signal source to be measured. That's not even the whole list. Of course you realize this it a challenging application. I am interested but need to know much more detail.

Regards, Bob

Temperature drift of measurement need to be only 1ppm/C on average and for operating conditions at 25C and inner temperature change, this drift need to be <5ppm at 25C +/-2C environmental temperature change. Measurement precision 1ppm equal to 20 bit in 24-bit ADC and measurement accuracy 10ppm equal to about 17-bit ADC is required. I am going to use 8-1/2 digit Keithley Multimeters for this calibration purpose.

So I understand you are controlling the ambient temperature of the circuit.

What is the nature of the signal source, is it low impedance, high impedance? Is it isolated?

What about the electromagnetic environment, is it noisy? Vibration? Anything else that may impact stability?

Signal source is amplified and buffered using low drift low noise preamplifier and can deliver 10mA easily for the ADC.

I am also planning to use current drivers for DAC for up to 100mA into load.

Signal source is single ended or differential?

This seems quite doable. What is your purpose to seek someone else to do the work?

I can do this work but I can not work cheap as I have a high demand for my time. If you are looking for low cost, I cannot help.

This work is for some one already doing this kind of work and hence, is just an additional work. I am not asking some one to start from fresh.

Bill of material for 8-channel ADC 24-bit using two 4 channel Linear Tech IC will be about US$50 including PCB. I will like to pay $1000 for 10 such PCBs.

18-bit DAC Bill of material for 8 channel will be $300 and for 10 such boards I can pay $ 5000

Putting both ICs on same board will make it for gain about US$2500 for a person and a professional in line can do it in 6 days easily. I believe this is good offer. I have a budget of US$6000 for 10 such hardware PCB containing 8-channel ADC 24-bit and 8 channel DAC 18-bit with 100mA current driver. Control thru SPI and few address select pins is OK to link the PCB to external uC.

Yes, I can also do this but I want some one with quality design experience to do it. I am more on experimental side and user of the hardware rather than a designer. I will prefer to pay the reasonable cost. I am not a PCB professional.

Hi Shyam,

It wasn't clear that you only needed someone to finish an existing design. That's not really my forte'. Good luck with your project.

Bob

I can suggest reinventing the wheel as companies like Linear Tech, ADI, Texas Instrument and few others have done great job in reaching the limits for precision part designs. Yes, there is still some hope in discrete designs but that needs years of work. I have limited time for all these.

Hi Shyam, Does your offer still exist. If it still exist I will be interested to take it up. Please let me know. My e-mail is ra68gi@yahoo.com Regards Raghunathan Chennai.

Are you want to produce electronic weighting system controller?

it seems other ask you for doing it.

there is still many parameters unknown.

for example, how much is output of dac?

how is work sequence for the 6 chennel? one to one?