Chart display and camera trigger

[Angar]

Hello,

I’m new to Labview and using it for my thesis to acquire data and initiate the image capturing of a camera. But I came across some problems with the data display and camera trigger, if anyone could offer some advice

My Hardware consists of a MC-USB-2404-UI DAQ-device (including MCCdaq-Drivers with Ulx-Libary and an extra LV vi pallet), a thermocouple type K and a TEMATEC pressure sensor MAP350-S / F (0-10V/0(4)-20mA). Since the DAQ-device supplies itself through USB with just 5V Power, I connected the pressure sensor in series with an additional 10V power supply unit.

The VI that I am constructing should read the measured values (pressure and temperature) and display them in a chart and on a numerical indicator. Above 200°C and 200bar the data logging should be manually started and a high-speed camera simultaneously triggered. Apart from the camera trigger, the VI is almost complete except for a few problems with measuring the value display.

Here are my problems:

1) How can I initiate the camera simultaneously with the data logging? Since the hs camera will capture more than 1000fps, I would restrict the image acquisition to a simple trigger that initiates the capturing. The appropriate VI’s IMAQ and IMAQdmx are already available. Should I create a new loop and connect it to my case-structure through a Rendezvous?  And what kind of vi’s do I need for a simple trigger?

2) Also I couldn’t figure out how to convert 1D-Array of Waveform to DBL or at least how to connect the data wire with a numerical indicator. The indicator is crucial for the manual start of the data logging.

3) Another problem is with the chart display. As soon as I start the data logging, the graph disappears and the chart displays only n-samples of the currant loop pass. The enlargement of the chart length history brings no improvement. Before the data logging is started the charts are showing the all points from the start. So what changes when I Press “Aufnahme starten” (start acquisition)?

Any ideas would be much appreciated.

[annav]

Hi Angar,

can you please explain your questions a little furhter?

1) as far as I understand you want to trigger the start of acquring images with your camera when the values get out of range. Is that correct?

2) I'm not sure what you mean there. Do you want to display the y-values in a numeric indicator? you can just use "Signalverlaufskomponenten lesen [get waveform components]" and wire the y-values to a indicator.

3) Can you post pictures of what happens here. one before the button was pressed and one afterwards? That would help to see what you see.

Thanks.

Anna

[Angar]

Hello annaei,

thanks for your quik help... the numeric indicator is now implemented. thanks to you.

Explaination:

1) I have construkted an experimental vessel, which builds up pressure through a stamp. There is a heating jacket around it and on the bottom is a sight glass to capture the intirior with a highspeed camera. The starting conditions for the experiment are 200bar and 200°C. So I will need to monitor the current state of the intirior to know when i can start the actual data logging. With the data logging i want to start my image acquisition silmutaneasly. 

3) For the Chart problem i attachted two pictures... After experimenting with the sample clock, reading vi and timing of the loop, i figured out that the greatest influence is the loop timing.

At 250ms (wait Xms multiple for loop pass) there is all data displayed even if i press the data logging button. At 100ms i was logging the data from 5s on and as one can see in the picture below the graph disappears after 28s. At 20ms loop pass interval the graph disappears randomly and with the data logging activated it is just a single point displayed.

In general the 250ms loop pass interval is a totally suitable solution for me, but i just can't help the feeling that the problem is not resolved. And i would like to know what i am doing wrong or what i could do better.

Thanks, Tobi.

[annav]

Hi Tobi,

thank you for the explanations.

1) You could create an event when your temperature and preassure reach 200. Read that event in another parrallel while loop and start your data logging and camera acquisition there. Here's a link how you can create and fire User Events.

3) I think it has something to do with your acquisition timing. Can you post the units of the rates? Is it 50 Hz?

Best regards,

Anna