Hi sir ,
Good afternoon,
i could not clearly understand the difference between, these two
iam using JS220
in device control i see the range of signal frequency (1kHz to 1Mhz)
and in user guide V1_7 the sampling rate is 2MSPS.
can you please elaborate with UI representation…
thanks.
@mliberty
hi sir
please check my query.
Hi @NGS - The JS220 is designed for 300 kHz bandwdith. In order to accurately capture this bandwidth, it uses a 6th order Butterworth anti-aliasing filter with 315 kHz bandwidth and a 2 Msps 16-bit SAR ADC. This prevents signal aliasing, but the sharp analog filter means almost no meaningful information is in the 500 kHz to 1 MHz bandwidth.
The JS220 immediately downsamples from 2 Msps to 1 Msps in the digital domain without affecting the 300 kHz bandwidth. This downsampling keeps the meaningful signal while allowing the data to fit over a USB 2.0 high-speed 480 MHz connection to the host. It also halves the computational requirements on the JS220 instrument, which helps with cost.
The host only sees the 1 Msps digitally downsampled data. With the more recent firmware and FPGA, you can select the digital decimate by 2 anti-aliasing filter, like this:
Joulescopes historically have used the wideband filter to preserve the frequency content, but this does add some overshoot. The sinc1 filter adds no overshoot, but is not as flat in the frequency domain.
For more detail on the filtering, see Section 15 of the Joulescope JS220 User’s Guide.
Hi sir, good morning…
yeah i trying to understand …
i was on leave, sorry for late reply…
thank you.
