High slew rate of level change when charting a boolean level change

[WillieNHS]

Hi Folks,

I`m an extremely new user and would like soome help figuring out why the slew rate when charted of a boolean level change is so high? If i wire a switch directly to a chart graph or if the output from my greater that decision changes state it seems to take a fixed time. I appreciate that noting happens instantly but the rate of change when compared with my analog input sqaure wave seems to take an age. Please review the block diagram attached and the front panel display. The triangles on the BeamON display chart illustrate the issue when compared against the Linac BeamON chart.

Any help greatly appreciated.

Thanks

Willie

[Henrik_Volkers]

The 'slew' rate on the chart could be even higher ... depending on the interpolation choosen 😉

Not your fault, you still need to learn a lot about data formats and some signal theory ...

Try to avoid the signal express vis and the 'dynamic data' even old veterans in LabVIEW don't know exactly whats going on in these 'dynamic wires' ..

Just because it wires together without breaking .. the result is unexpected/unknown(?) ..

a boolean is true/false or 1/0 so the slew rate in real time is infinite (or depends on your sample rate in time discrete systems)

Seems that your boolean is sampled once per loop ..

BTW a boolean switch has different 'tastes' ... how it react on interaction..  see help

[WillieNHS]

Hi Henrik,

Thanks for your pointers.

May I ask, how do I avoid the signal express vis? can you suggest a method to avoid dynamic data use?

How may I increase the sample loop frequency to sample the Boolean states more often?

Thanks again.

Willie

[Henrik_Volkers]

Do you need to read the Beam-ON via a boolean frontpanel input? ...

Can't you use a digital input of a DAQ?

However, Look up and learn how to use events.

Avoiding express vis /dynamic datatype is easy.. just use the extract single/multi tone information vi

(learn to use the quick drop.. CTRL-Space 😉 )

Every wire  (and VI output) has a datatype you need to regard. If you mix up arrays and single values you need to understand what the operation you use to mix them is doing ... (read help)

If a red dot is shown in the diagram LabVIEW converts the datatype of the wire to match the input datatype of the vi/funktion you use. That may or may not result in the result you expect.

(The dynamic datatype eases this confusion... there are a lot of LV programmers that stricly try to avoid this datatype... me included)

[Henrik_Volkers]

Maybe you should explain what you measure and what information you want to extract...

(Not so obvious by you code anlone ..)

[WillieNHS]

Hi Henrik,

I`m using and old PMD 1208fs 4 channel DAQ to sample two waveforms, one being a roughly sinusoidal waveform at around 0.5 Hz. The second waveform comprises square pulses at around 300Hz. The idea is to detect when the square wave frequency goes above 50 Hz for example and I would like to generate a another square wave which is high for the duration of the original square wave being above 50 Hz. I then intend to relate the generated square wave mathematically to the original sinusoidal wave to note any change in overlap. Its for a Radiotherapy systems performance monitoring phantom. I do appreciate your help and I`m aware that I`ve a log way to go! I`m finding LabView to be quite hard to get started with but I`m willing to put the effort in. I was able to construct a working version of this idea using DASYLab in a day or so, and was hoping to get into LabView but realise its a very different level to DASYLab.

Thanks

Willie

[WillieNHS]

Having not been able to get around the slew issue during a Boolean transition. I`ve decided to try to accept this situation and try to do the analysis between the slewed wave and my square wave. Can which module would be good to look at for trying to compare the pulse width of the two waveforms and provide numerical data relative to the differences between them?

Thanks

Willie

[WillieNHS]

Perhaps someone could point me in the direction of some reading material if my basic ideas here are wrong? My issue remains that in the case of my greater than module where im detecting a level higher than 2.5 i get an instant transition to logic level 1, but the frequency detect over 50 Hz still displays high slew. If this is to do with the loop time being related to the samples pere channel and sample rate then why would this effect one module but not the same module in the same while loop? I have taken note of the commments relaiting to dynamic data type, perhaps a pointer to allow me to avoid this data type may point me in the right direction?

Thanks

Willie