NI-Scope Range Settings

[Son_La]

PXIe5172, Measurement Studio 2019, VS 2019

I hope I get some helps here.  On the NI-Scope SFP the channel Volt/Div can set from 200uV to 20V.  After instantiate the object and reset the scope to default I set the range using this call:

Pxie5172Scope.Channels[channelName].Range = voltRange

on the SFP I can see that I can set the "Volt per Div" to all the one they provide but in my code when I try to set the voltRange to different values manually I found that I I can only set to 20mVolt/Div by setting the voltRange to 0.2V anything smaller than that will set the Volt/Div to 20mV

When I start increate the voltRange from 0.3 to 0.7 the volt/Div will only stay at 50mV/Div settting.  And then I increase the voltRange between 0.8V to 1.5V I can only get one setting of 100mV/Div ... You get the picture

Look like there is some problem with the Range resolutions but I can figure out what cause this in my application.  My application starts up with the default setting.  I turned on CH0 with immediate trigger mode (edge mode will not make any different) and that start changing the Volt Per Div parameter.

I hope someone can help. 

[santo_13]

I guess it is working properly as you have only a handful of hardware ranges available on the scope and hence any value you set choose the closest best range available.

If the SFP is supporting any arbitrary range, I would guess it is not a real hardware range rather they scale it in the SFP application and does not reflect the actual range the hardware is operating.

This article explains the coercing behavior of the vertical range method.

https://www.ni.com/docs/en-US/bundle/ni-scope/page/digitizers/vertical_parameters.html

[Son_La]

Thank you for the information.  The SFP are using the same PXIe5172 as I do, they scaled the range to set the volt/div on the display by setting the range =  multiplying the select volt/div on the GUI by 10 (the number of divisions on a scope) and that gives the correct volt/div displayed on the SFP - As how I understand it. With the scope input impedance set to 1MOhm the vertical range of the PXIe5172 is defined between 0.2V to 80V so with the scaling the minimum volt/div can only be 20mV but the SFP min volt/div is at 200uV and the max is 20V.  This is very confusing 

[Son_La]

@santo_13.  I eventually put the debug codes into my application and printed out the actual Range of the device each time I increase the range settings and figure out you are correct, the SFP range and the hardware are not the same they must have put some fancy codes behind the SFP.  The number is very wild and I am still unable to figure out what the formula actually is.  For example, when I set the range to 0.2 the actual range the device set to is 0.2 but when I set it to 0.3 the device range will jump to 0.7. Or when I set the range to 1.4 the actual range readout is 1.4 but when I increased it to 1.5 the actual range jumps to 5.  

I eventually confirmed that I can only set the volt/div to these: 20mV, 50mV, 100mV, 500mV, 1V, 5V, and 10V.  Which compared to the SFP of 200uA to 20V is way off.  In between the SFP and the documentation I still can't believe NI makes it this hard to figure it out.

Engineer Ambitiously = Engineer Ambiguously 

[erik2]

I'm really looking forward to try and log some problems I have been noticing in the last 3 years in my house. I study Electronics and Telecommunications but I still don't have proper expensive gear.. But i've seen some USB oscilloscopes, PCI ones too and I really wanted to ask someone that has one.

Any kind of oscilloscope for PC, that I can use to record data 24/7, and what's the sample rate and size of data I'll have to look forward to?

[santo_13]

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@Son_La wrote:

@santo_13.  I eventually put the debug codes into my application and printed out the actual Range of the device each time I increase the range settings and figure out you are correct, the SFP range and the hardware are not the same they must have put some fancy codes behind the SFP.  The number is very wild and I am still unable to figure out what the formula actually is.  For example, when I set the range to 0.2 the actual range the device set to is 0.2 but when I set it to 0.3 the device range will jump to 0.7. Or when I set the range to 1.4 the actual range readout is 1.4 but when I increased it to 1.5 the actual range jumps to 5.  

I eventually confirmed that I can only set the volt/div to these: 20mV, 50mV, 100mV, 500mV, 1V, 5V, and 10V.  Which compared to the SFP of 200uA to 20V is way off.  In between the SFP and the documentation I still can't believe NI makes it this hard to figure it out.

Engineer Ambitiously = Engineer Ambiguously 

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These values make sense to me 20mV, 50mV, 100mV, 500mV, 1V, 5V, and 10V, the SFP on the other hand is common for all models of NI Scopes and could show ranges that are not supported by your model.

[santo_13]

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@erik2 wrote:

I'm really looking forward to try and log some problems I have been noticing in the last 3 years in my house. I study Electronics and Telecommunications but I still don't have proper expensive gear.. But i've seen some USB oscilloscopes, PCI ones too and I really wanted to ask someone that has one.

Any kind of oscilloscope for PC, that I can use to record data 24/7, and what's the sample rate and size of data I'll have to look forward to?

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Your question is in no way related to this discussion, please create a new topic/thread for your question.

Most scopes support continuous capture but streaming them to disk would be the challenge at high sample rates. What is your budget? a DAQ could do the same thing at a better price point.