about rise time test

[LIONCSU]

Hi,
Use Transition Measurements to test rise time as appendix in detail.My question:
1. Is the program structure reasonable?
2. When the RAMP TIME of amplifier is fixed, the DURATION varies to the different time of input control Am.
3. The duration ERROR is out of allowance.
Hope you give me a resolution.
Thanks!
Regards,
XU

[Erick]

Hi Xu,

I understand that you are wanting to calculate the rise time of a signal coming into your NI 4472 board. I'm assuming the NI 5411 is stimulating an external amplifier? Please include more information about your application and the routing of the different signals involved so I have a better idea of how to best implement a solution.

Also, are you receiving an error with an error code when you run the program? Or is it just outputting a value you don't expect. If you are receiving an error please include the error number and the description.

The NI 4472 is capable of making rise time measurements but I would recommend using one of the NI high-speed digitizers which have built in functionality for making rise and fall time measurements. They also make much more precise timing measurements due to their higher sampling rates. If you have an NI digitizer I would give that a try. If you only have the NI 4472 then I can help with that also. I just need more information about your application.

Regards,

Erick D.
NI Applications Engineer

[LIONCSU]

Hi,Erick
Thank you help me and answer your issue as follow
The 'amplifier' is to be tested object. It can generate RAMP signal,i.e. PXI5411 generates a pulse DC voltage (0 to 5 input by Am a numeric control in the example). The AMPLIFIER will output RAMP Voltage sampled by PXI4472 then Calculating its RISE TIME.
I repeated test the RISE TIME. The result is a variation with different parameter of SAMPLES TO READ. If the parameter less than 1024,error message will popup: increase buffer size to read. I thought the result accords to real time with 1024s, the others may be not trusted with the parameters of samples to read (e.g. 8192,10240 etc.).
I couldn't understand.
May I introduce my issue clearly?
Besides PXI4472,I have PXI4072. Would you implement a solution?
Regards,
XU

[Erick]

Hi Xu,

Thanks for the description. I understand you are getting an error when setting the "Samples to Read" input to a value less than 1024. The error indicates that you need to increase the buffer size. I tried to reproduce this error but was unable to. Would you mind sending me several screenshots.

1) A screenshot image of your front panel so I can see what your controls are set to.

2) A screenshot of the error window when the error occurs.

Also any other information that would help me reproduce the issue would be much appreciated.

Thanks!

Erick

[LIONCSU]

Dear Erick,
Sorry,because of some things to be processed,I couldn't send some information on time. Here I send the screenshot captured running the program with 512 of samples to read as soon as prompted the error divided into three pictures to fully see the error information. I hope you give me a better idea to solve the trouble.
Thanks,
XU

[Erick]

Hi Xu,

Thanks for those screenshots. The error -200279 is occurring because the FIFO memory onboard the NI 4472 is being filled before the computer can fetch the data off the board. I'm not sure what sampling rate you are running at, but your fetch size (number of samples per channel) is quite small at only 512. Some ways to keep this error from occurring is to either lower the sampling rate, or increase the "number of samples per channel" input for the DAQmx Read VI. This is also dependent on computer speed so make sure all programs that you are not currently using are closed. If your computer is running very slow then it is performing less fetches and the NI 4472 onboard memory fills more quickly.

Let me know if you have any other questions.

Erick