NI 5112 bandwidth

[nyborn]

Hi:

Here is the message for the definition of bandwidth.

1. All analog devices have a frequency response curve. With oscilloscopes, the bandwidth usually refers to the point at which input signals are attenuated 3dB from their actual values. The native bandwidth of the 5112 is 100MHz, so 100MHz signals will be attenuated by about 50%, 200MHz signals by a lot more, 50MHz signals almost no attenuation. With 20MHz bandwidth, this -3dB point is moved to 20MHz. The 20MHz bandwidth is sometimes referred to as a noise filter. Use it if you have no frequency components in your signal over 20MHz and you want to reduce noise.

So, the only time that I determine to use 100MHz and 20MHz is to see if I get the correct waveform. If I use the 20MHz bandwidth and I got the waveform. Then 20Mhz is my correct setting, is that correct?

Also, is bandwidth funtion to attenuate the input signal? Is it because we need to filter the noise of the signal?

[kalyanramuv]

Hello,

I haven't completely understood your question. When you set bandwidth to 20MHz, it is similar to applying 20MHz low pass filter. Typically to eliminate high frequency noise from your system, bandwidth is adjusted. Now as for your application what is the source of the input signal?

Typically for most applications, depending on application you can estimate of the bandwidth of the signal from the source. Using that knowledge bandwidth can be adjusted accordingly. In other words, it is important to understand how the signal from your source is bandlimited.

Now, if  the estimated bandwidth of signal is unknown, you can apply with settings to properly see the signal. One way to look at the problem is to use highest bandwidth always and acquire the signal. In this way, you wouldn't have to worry about bandwidth settings. However your application dictates what bandwidth is best.

Good Luck on your project !

Kalyan