I've read that the actual sample rate for the AD2 is always 100 MSPS, but when a frequency of say 100 KSPS is used (1000X slower than the base rate), the FPGA averages the points to generate a point every 10 microseconds (when using the average filter). This would give 1000 points that could be averaged for each data point output by the FPGA, and with a 14-bit ADC, this oversampling and averaging should increase the resolution by N bits where 4^N=# averages (in this case 1000 would give nearly a 5 bit increase in resolution and almost 19 bits resolution). However the resolution specification is .32mV (for high gain) which corresponds to ~5.5V full scale/14 bits, and my measurements have confirmed the quantization noise is ~.32mV suggesting no improvement in resolution from oversampling. Is this a limitation of the FPGA programming/precision and can it be improved to make this already great device have more effective number of bits for lower scan frequencies? Are there any improvements in the AD3 with regards to bit depth at lower scan rates?
Question
Walid
Hi,
I've read that the actual sample rate for the AD2 is always 100 MSPS, but when a frequency of say 100 KSPS is used (1000X slower than the base rate), the FPGA averages the points to generate a point every 10 microseconds (when using the average filter). This would give 1000 points that could be averaged for each data point output by the FPGA, and with a 14-bit ADC, this oversampling and averaging should increase the resolution by N bits where 4^N=# averages (in this case 1000 would give nearly a 5 bit increase in resolution and almost 19 bits resolution). However the resolution specification is .32mV (for high gain) which corresponds to ~5.5V full scale/14 bits, and my measurements have confirmed the quantization noise is ~.32mV suggesting no improvement in resolution from oversampling. Is this a limitation of the FPGA programming/precision and can it be improved to make this already great device have more effective number of bits for lower scan frequencies? Are there any improvements in the AD3 with regards to bit depth at lower scan rates?
Thanks,
Walid
Link to comment
Share on other sites
1 answer to this question
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now