Network Analyser, what's MaxGain doing?

[hugocoolens]

I'm a bit confused about use and internals of the MaxGain field when running the Network Analyser:

1. Does it change the accuracy of the plots made by the analyser?

2. When I have entered the values for the Bode Scale Top and Range, what's the use then of entering a value for MaxGain?

 

could someone clarify this?

thanks in advance

hugo

 

 

[attila]

The Amplitude x Gain x 2 specifies the scope channel range. Having the peak2peak level of the signal close to the scope channel range will result the best resolution.

The Scope channels on EExplorer have many physical range settings, but on Discovery these have two ranges. With this device the best resolution can be achieved having 4V pk2pk signal, like: 2V amplitude and 1X gain.

Resolution by noise elimination can be increased configuring larger number of periods, see:

 

The Bode Scale sets the plot margins only.

[hugocoolens]

The Amplitude x Gain x 2 specifies the scope channel range. Having the peak2peak level of the signal close to the scope channel range will result the best resolution.

The Scope channels on EExplorer have many physical range settings, but on Discovery these have two ranges. With this device the best resolution can be achieved having 4V pk2pk signal, like: 2V amplitude and 1X gain.

Resolution by noise elimination can be increased configuring larger number of periods, see:

 

The Bode Scale sets the plot margins only.

I'm using the Discovery, do I understand it correctly I should use e.g. a MaxGain-setting  of 10 if I expect the output signal amplitude to be less then or equal to 200mV?

 

kind regards,

hugo

[attila]

Gain 10 will ensure that the scope channel will capture the AWG signal amplified 10 times by the filter circuit. Having 2V AWG amplitude signal with scope channel gain 10 will capture up 20V amplitude (40V pk2pk) filter output.

[hugocoolens]

Gain 10 will ensure that the scope channel will capture the AWG signal amplified 10 times by the filter circuit. Having 2V AWG amplitude signal with scope channel gain 10 will capture up 20V amplitude (40V pk2pk) filter output.

Sorry, but I still don't get it. More questions pop up:

 

1. I thought the Analog Discovery had only two gain settings "1:1 or 1:10" and this is achieved by an attenuator in the circuit. MaxGain doesn't seem to be related to these two settings?

2. As there are _two_ channels, how then can you achieve best performance with _one_ MaxGain setting

3. Should the user try to present 4Vptp signals to the internal ADCs for best performance

4. Is MaxGain just a software multiplication?

 

Maybe some examples could clearify the use of MaxGain:

e.g. I have on channel 1 a 200mVptp signal and on channel 2 I expect a signal which will be max. 3Vptp, how do I calculate the best setting for MaxGain in this situation

 

thanks in advance

hugo

[attila]

The gain in Network Analyzer can be specified for each channel separately. This multiplied with the specified amplitude (in software) is used to configure the range of scope channels to make sure the input signal does not get into limitation.

 

The MaxGain option is intended to be able to set common gain for the channels. This is useful with EExplorer with 4 channels and ~60 physical gains.

 

The Analog Discovery scope channels have two physical gain settings, 5V and 50V pk2pk range. 

 

With Discovery if you set 2V amplitude and gain 1, we are expecting 4V pk2pk input signal the channel range will be set to 5V. With 100mV amplitude and gain 0.1, the expected pk2pk range is 20mV, the scope channel range will be the same 5V. For 2V amplitude and gain 2, expecting 8V signal the range will be set to 50V.

To generate 200mV pk2pk signal set the amplitude to 100mV and expecting 3V pk2pk means gain of 15 (3/0.2).

 

In case the input voltages on any scope channel enter in limitation warning will be displayed. The Time view can helpful in adjusting the correct scope offset and range (gain) settings.