sampling rate

[mhs100]

Hi all

I have made the usb daq card, i want to calculate its sample rate. Can anyone please tell me how to calculate?

Regards

mhs100

[LV_Pro]

Not sure what you mean "made the usb daq card", but if you are asking how to determine what sample rate to use, it depends on the highest frequency of the signal you are trying to sample. The sample rate should be greater than twice the frequency of the highest frequency component of the signal you are interested in, a basic concept in data sampling. If you have actually "made" a usb daq card, the sampling rate is dependent on how it is set up, with the front end being the first thing you should look at.

[Dennis_Knutson]

Since it is your design, I would presume that you know the rate of the sample clock that you are feeding to the ADC.

[mhs100]

Actually i have made the pic18F4550 based data acquisition card having interface on labview. I want to find out its sampling rate by using labview. Is it possible? if yes then how?  it has 8 analog input , 2 pwm outputs 16 digital I/Os.

Any help will be greatly appreciated.

Regards

mhs100

[mhs100]

Message Edited by mhs100 on 10-29-2009 12:53 PM

[LV_Pro]

I am still not sure what you are trying to do.  If you have built a DAQ system you would know better how the sampling rate is set up. If your question is whether LabVIEW can query the card, or set the card I'm not sure we can help unless we had much more information about your card. I'm guessing that it being a PIC based system that you might be communicating serially, so I'm guessing that you send some command to set its parameters. Or the scan rate is hardware controlled, then there may be a command to ask what it is, but just knowing what PIC processor is used won't probably help.

[hecmar.arreola]

Read http://ww1.microchip.com/downloads/en/DeviceDoc/39632e.pdf section 21.0.  Thats your microcontroller's datasheet

[LV_Pro]

It looks as though you can set the sampling rate, through LabVIEW, by setting the configuration of the sampling clock, from table 21-1 in the pic18F4550 datasheet, but I see nothing that allows you to read back this setting, although I haven't done an intensive search of the documents.

[mhs100]

Hi

i dont want to set the sampling rate of my daq card. My question is that is there any way to calculate the sample rate of my daq card by means of programming in labview? I have also seen the tutorials in which methods to calculate the sample rate of NI daq card are mentioned but  this is my own built daq card and it definitely has some sampling speed but how to determine it?

I have also read the adc section of the datasheet of pic18f4550 but still i dont know what the sampling rate is?

[Dennis_Knutson]

There are no 'methods' to calculate the sample rate of an NI DAQ card. The sample rate is something you set and read back. Unless your firmware provides a means of querying the device, there is nothing that LabVIEW can do )at least with any degree of accuracy). I have not read the specs very closely but it seems all of the information is there for you. If you cannot understand the specs or the firmware for the device, take a scope and probe the scope line.