Analog Discovery: Data Logger issue

[jfdo]

Hello Digilent team and forum members,

 

I bought the Analog Discovery in 2015 while I was in Germany (but now in Australia). But I never use it until a few days ago.

 

I downloaded the software/installed and connected the device. 

Did simple experiment, generating 1kHz sine wave and observing it in the scope.

I tried to see the same in the data logger and data logger doesn't show the waveform/data I expect, 1kHz sine wave signal.

 

I already saw the videos/tutorials about data logger and they do not explain how to measure/record some data using and data logger and how to use math functions, the syntax etc.

 

I have very simple setup. I appreciate if you could answer the followings or pass this email to the relevant person. I have spent enough hours without any input/document and success.

 

1) Analog Discovery pin W1 has been connected to the 1+ (scope channel 1 input) and ground (black wire) has been connected to the 1- (scope channel 1 ground)

 

2) Generated a 1kHz sine wave with 1V amplitude using "Wave generator". Please see the attached print screen ("Waveform").

 

3) I can see my waveform in the scope.  Please see the attached print screen ("Scope").

 

4) But I CAN NOT SEE MY WAVEFORM IN THE DATA LOGGER!  Please see the attached print screen ("Data Logger_1"). It has default "Items" (C1 DC, True RMS, AC RMS). Can't I add more items?

 

5) Can't I just display the raw signal in the data logger, as I can see in scope window?

 

6) When I tried to add a mat function, abs(), it is throwing an error "Reference Error: can not find the variable C1: Line 0".   Please see the attached print screen ("Data Logger_2").

 

7) What are the names of the input variables to the scope?

 

Thank you

 

Best Regards

[attila]

Hi @jfdo

The frequency range based on update rate and device buffer size is shown on the top.
Theoretically 100ms could measure 10Hz, but due to incomplete cycles (like 12.5Hz in 100ms does 125% period) would result in high AC errors, so 100ms is recommended for 40 Hz and above.

[attila]

Hi @jfdo

The Voltmeter does not provide access to the oscilloscope acquisition data but only to the earlier listed measurements: C1DC, C1TrueRMS, C1ACRMS, C2DC...

[jfdo]

ok thanks. So, I suppose xi is the ith input value (voltage) and N is the number of samples?

How do we acquire xi from the data-logger?

[attila]

Hi @jfdo

See the WaveForms application Help:
For the True RMS value, the same acquisition is used as for the DC voltage, and the value is calculated with the formula Sqrt( sum( xi ^ 2 ) / N ). The AC RMS value is calculated with the formula Sqrt( sum( (xi - dc) ^ 2 ) / N ).

[jfdo]

Thanks Attila.

Can the data logger display any AC signal. I know we have variables C1TrueRMS and C1ACRMS. Do they actually display the true AC signal.

Cheers

 

[attila]

Hi @jfdo

You can find the variables and common functions in the editor window, see C1DC, C1TrueRMS, ..., abs(), pow(,)...

 

[jfdo]

Hi,

I connected the device and repeated the experiment but still I don't get any sensible data plot. I would like to ask what settings they have made in the wave generator and logger to get the following plots in the logger? This plot can be found in the following link, in the Data Logger section.

 https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/reference-manual?s[]=data&s[]=logger

 

Although I set the amplitudes in the wave generator to be 1V-3V I always get some mVs in C1 D, C1 True RMS and C1 AC RMS? And no sensible wave waveform can be seen.

Do I have to calibrate the device? If so, can I use the same Analog Discover 2 software to calibrate my Analog Discovery (Legacy)?

 

* Confusing syntax to add math channels in the data logger.
A) According to some tutorials the, the input variable for math channels is C1 in data logger. e.g. C1 DC, C1 TrueRMS, abs(C1) etc. 

In another tutorial it says " The Data logger tool makes use of the same input channels as the Oscilloscope tool. These are labeled “1 +/-” for C1 and “2 +/-” for C2 on the Analog Discovery 2 30-pin header. Use of the Data Logger will lock out the Oscilloscope tool".

Which one is correct? 

If I use the syntax as in A) I get error other than standard 3 math operations (C1 DC, C1 TrueRMS, C1 AC RMS). If I use abs(C1) there is an reference error

 What is the syntax to write a math equation in the data logger math channel?

Thank you.

 

[attila]

The demo mode is to show the software features but not all the functions are working exactly as it would with a real device.
Please repeat your experiment using the device.

[jfdo]

I set the wave generator frequencies in the range 5Hz to 50Hz  in the demo mode and still the data logger doesn't show any sensible data plot.

Any idea?

[jfdo]

By the way what is the highest frequency of an AC signal that the data logger can safely display? 

Highest update rate in data logger is 100ms. So the highest frequency that the data logger can display is 10 Hz?

[jfdo]

Thanks for the input.

What is the correct syntax to read the input and perform a mathematical operation in Data Logger?

 

 

[attila]

Hi @jfdo

The Data Logger is intended for simple and slow AC/DC signals. For other complex measurements use the Scope, Spectrum, Network or Impedance Analyzer interfaces.
In Logger the DC measures the average for each update period. As you can see on the top the RMS for 1 sec Update rate will capture 4Hz to 2kHz AC signals.

[jfdo]

Many Thanks JColvin for the quick reply.

[jfdo]

3 minutes ago, JColvin said:

Hi @jfdo,

The URL doesn't change when we move a thread so it can always be readily found with the existing link, but the section of the Forum did change to Scopes and Instruments where the creator of the WaveForms software commonly looks.

Thanks,
JColvin

Many Thanks JColvin for the quick reply.

5 hours ago, jpeyron said:

Hi @jfdo,

I have moved your thread to a better section where more Analog Discovery and waverforms experienced engineers look. Also I would suggest looking at the tutorials ,example and community projects on the resource center here for the Analog Discovery and here for the Analog Discovery 2 if you haven't yet.

thank you,

Jon

 

[JColvin]

Hi @jfdo,

The URL doesn't change when we move a thread so it can always be readily found with the existing link, but the section of the Forum did change to Scopes and Instruments where the creator of the WaveForms software commonly looks.

Thanks,
JColvin

[jfdo]

Hi Jon,

Thank you for the response, and moving my post to an appropriate section.

But where did you move the post? (where is this section where experienced engineers look ?)  It would have been helpful if you had sent the link.

I already had a go with the tutorials with the links you have sent. But I could not get any input for my issue with the data logger.

Awaiting to hear.

Cheers

Julian

[jpeyron]

Hi @jfdo,

I have moved your thread to a better section where more Analog Discovery and waverforms experienced engineers look. Also I would suggest looking at the tutorials ,example and community projects on the resource center here for the Analog Discovery and here for the Analog Discovery 2 if you haven't yet.

thank you,

Jon