Conserving Wi-Fi bandwidth by reducing sample rate?

[MaxR]

Hi,

I'd like to take samples every 5 minutes with a wireless connection between my DAQ and laptop using SignalExpress in the interest of conserving bandwidth. Is this possible? Thank you for your help.

P.S: I made sure to try and search for the answer but was not successful.

[Miro_T]

MaxR

I have hard time understanding your question or what are you trying to achieve.

What kind of wireless DAQ are you using? Is it cDAQ-9191?

 What is the big picture of this problem?

Lastly, how fast are you trying to sample?

[MaxR]

Thank you for your reply. I don't have a specfic DAQ yet - I am speccing out a system right now. We are collecting data from thermocouples in an electrically noisy environment. I want to avoid running cables as much as possible due to the noise. Thus, I was considering using a wireless DAQ to relay the data to my computer in the adjacent room. The concern is that I will be hogging too much bandwidth from the wireless router which serves many computers. Since I only need data updates every couple minutes, I was hoping that the reduced sample rate would result in reduced wireless traffic.

Max

[Miro_T]

Max,

Fundamentally, if your device is acquiring less data then there is less data transferred over the network, thus using less bandwidth.

One thing that is boggling my mind about this…. Why would wireless connection be better in eliminating electrical noise then wired? Isnt isolated wired connection better for noisy environment?

I am not trying to question your application, just brainstorming the idea

[MaxR]

You raise an excellent point. RF signals are probably susceptible to the same electrical noise. I am considering using ethernet instead.

Are you sure that sample rate does not refer to how often LabVIEW updates it's measurement? I fear that data is streamed from the DAQ to the computer at the maximum rate and the sample rate actually just changes how often LabVIEW "checks" the data.

[Miro_T]

Max,

There are two forms of DAQ sampling, software timed and hardware time.

Software timed - device provides one sample per each LabVIEW request. For example, you have a while loop that calls DAQmx read every 0.5s. You are doing 2 samples per second

Hardwared timed – device is using onboard clock to sample incoming signal. Sampled data are stored on the hardware buffer and LabVIEW reads data off the hardware buffer.

What you described in your statement above is software time (on-demand). In order to determine if this type of sampling is efficient for you, you need to know your sampling rate.

What is your desired sample rate? Since you are looking to do temperature measurements then I am assuming it would be slow sample rate????

[MaxR]

Very informative. Thank you for your response. You are correct I need a slow sample rate (1-5 minutes).

[Miro_T]

Max,

one sample every 1-5minutes is very slow and you should not have any problem doing Software timed sampling. 

I hope this helps