flagging events?

[labnoob]

hi all, what would be the best way to implement in my system for whcih to flag events such as voltage dips, flicker etc.

thanks

[smercurio_fc]

Considering that you've told us nothing about your system it's going to be a bit difficult to provide suggestions, wouldn't you agree?

[labnoob]

multifucntion DAQ. sampling mains, writing the data to file, then analysing it. not sure what else to say really!

[Stuart_R]

When you say flag events, what exactly do you mean or require? Do you just need some sort of method to display this within your VI, such as an LED, do you need to log this to file or similar? Or are you asking how to detect the voltage dips etc?

Give me some more info on what you actually mean and I'll happily advise you further.

Thanks,

Stuart

[Stuart_R]

Also, how are you measureing mains voltage using a multifunction DAQ? If mains means 240V, you must be using some sort of Signal Conditioning??

[labnoob]

hi, thanks for replying. yes im using an interface whcih i designed and built. it steps the voltage down to 5V and provides galvanic isolation, whilst passing all the harmonic frequncies. im also measuring the current too.

im pretty much looking for everything you suggested! im an electronics engineer you see: i appreciatte all your help.

thanks.

[Stuart_R]

Any chance you can post the code that you've got and I'll look at it and maybe add in the required functionality that you require?

[labnoob]

eh, sure! 🙂 please understand thats its still very much in development, and ive never used labview before,  so dont laught at it! lol 🙂 also i was playing around with the 'read file' vi last night and it kinda stopped working. its work in progress tho!

im basically needing to implement functionality that will record evenets if for example the nominal freq goes below or above what the standards say as documented below. also for other phenomena such as Supply voltage variations, Flicker severity etec as documented below.

thanks again for your time.

Power frequency

The nominal frequency of the supply voltage shall be 50 Hz. Under normal operating conditions

the mean value of the fundamental frequency measured over 10 s shall be within a range of

- for systems with synchronous connection to an interconnected system

50 Hz ± 1 % (i.e. 49,5 ... 50,5 Hz) during 99,5 % of a year,

50 Hz + 4 %/- 6 % (i.e. 47 ... 52 Hz) during 100 % of the time.

- for systems with no synchronous connection to an interconnected system (e.g. supply

systems on certain islands)

50 Hz ± 2 % (i.e. 49 ... 51 Hz) during 95 % of a week,

50 Hz ± 15 % (i.e. 42,5 ... 57,5 Hz) during 100 % of the time.

[Stuart_R]

OK, I've had a quick look at the code and can see some potential problems. Are you acquiring the data, logging it to a text file and then reading it back for analysis? On first look it looks like you are trying to read back the data as a binary file not a ascii text file. This will cause you issues and if is incorrect, try reading the data back using the Read LabVIEW measurement file express vi.

Does the frequency analysis that you are carrying out work OK? i.e. does it calculate the correct frequency data that you require? From this data you could then start using the comparison tools such as greater than or equal to, in order to comapare the frequency against a limit. If you exceeed the limit then you turn on a front panel LED. This could also be logged to file too.

Let me know your thoughts.

[labnoob]

not really mate, i ony just added in that freq part so not had much time to play with it yet. im not entirely sure which format i need it in. i.e asci or text. both maybe! I’d like to have a copy of the actual waveform, but i guess a text file of logged events would be great also. what format do i need it in if i want to do analysis on it once i collect all the data. i.e FFT etc.

im liking your thoughts mate. kinda what i had in mind, but i was just abit unsure how to code it. Should i be using triggers in my acquisition? what exactly are the point of them anyway? will it mean i can acquire waves at the zero crossovers, for example, if  i need 10 cycles from a 10Hz signal.,  i could request 1000 S/s to read, at a freq of 1000 Hz. but this may not necessarily give back 10 complete cycles! Suggestions?

thanks again.