scb 68-How to simulate a digital output in the Labview GUI

[sharkpitt]

Hello there my name is Shafik and I'm from Malaysia.I'm a relatively new user of SCB 68 multifunction DAQ. My team was asked to connect an LM35DZ temperature sensor to the card and produce the necessary output via the GUI. Throught trial and error we managed to do so.It was quite straight forward. We've simulated the output voltage and translate it into real time temperature (degree C) in the LabVIEW GUI.

DAQ-->Multiplier(since the LM35DZ produces a linear voltage to temperature,sensitivity 0.01V = 1 degree C)-->GUI Thermometer

How do we simulate the output voltage signal in a digital form in the GUI?Do we have to connect the analog output from the LM35 to an ADC in the GUI?We tried doing so but the result is unsatisfactory since we can't produce the same output temperature as the direct connection.From the same output we've connected it to the ADC block in the GUI and then using  arithmetic block we formulate the ADC conversion formula(Which I think not necessary.Since it should be done by the ADC right?)

or

(I've yet to try this)We pass the output signal through a series of  formulas using the arithmetic options and then pass it through the ADC. Hopefully it produces a the necessary output.

or

Give it a good X5 gain,run it through tha ADC....anymore ideas?*grins*

or

I got the whole concept wrong?*grins.....scratching head*Hmmphh......help anyone :manhappy:

Thank you in advance

[Dennis_Knutson]

The first thing you need to do is understand that the SCB 68 is not a data acquisition device. It is just a dumb terminal block. Do you have an actual DAQ device or do you want to simulate everything? What exactly do you mean by simulate the output in a digital form?

[sharkpitt]

Actually the lecturer wanted us to simulate an output using the SCB 68. Since I'm using the temp sensor he wanted us to show the necessary output in the LabVIEW GUI. Me managed to do so.

We connected the LM35DZ temp sensor to the terminal block,create a GUI simulation and got the output before and after amplification using the multiplier arithmetic tool.Quite straight forward actually.

What I meant from a digital output is that we were asked based on the output in the GUI to create an output made up of digital signal waveform. An analog to digital conversion of the output signal.We are still trying to go about this.

I hope I'm giving you the right picture.

Thank you for your reply and clarification.

[Dennis_Knutson]

You are not actually simulating a scb 68 because it is not possible to simulate a connector block. It is possible to simulate an actual DAQ board that is connected to a temperature sensor through the connector block and not create your own simulation code. You are using a real scb 68 and that what was confusing to me.

If I understand correctly, if your analog output is a waveform data type, then all you have to do is wire that to the Analog to Digital function on the waveform palette. You can choose the resolution (number of bits), data format, and range.  Display the output of that function on a Digital Waveform Graph.

[sharkpitt]

Yup you understood me correctly. Thanks for the tip.

[sharkpitt]

Now that I've managed to do so and produce a digital output in the LabView GUI and obtain a readout is it possible the digital values of '1'(High +5V) and '0' can be utilized to trigger say a switch(BJT,MOSFET or an optocoupler) on the same SCB 68 card?

Input transducer LM35DZ > LabView GUI : Show output value(Temperature) > Comparator (also in LabView GUI) -High or Low state? > Trigger a switch(external cicuit-possible connected on the same DAQ)....

hmmphhhh.........thanks!

[Dennis_Knutson]

Only if you have an actual DAQ board in the pc. All that you have talked about is the SCB-68.

[Neal M]

Hello sharkpitt,

Dennis is right, how you accomplish this depends on what DAQ card you have.  As he said before, the SCB 68 is just a terminal block.  All it does is provide easy access to specific pins, it does not actually do any measurements.  You can find what card you have by opening Measurement and Automation Explorer:



navigating in the tree to My System»Devices and Interfaces»NI-DAQmx Devices, your device should be listed here:



Once we know what DAQ card you have, then there are several ways to accomplish what you are trying to do.  The easiest method would be to directly output the digital waveform (using the DAQ Assistant) on a digital line (standard TTL signal for most cards, 5V high, 0V low). Then, depending on the switch, you could use that digital output to drive the switch or possibly use a transistor or something similar. If you do not have any digital lines on your card, then things get more complicated.  If thats the case, post back and we can try some other methods.

Some of our cards (for example, the USB-6525) actually have this functionality built in to them (you control a relay on the card using a digital signal),  but again, this depends on what DAQ card you have.

Message Edited by Neal M on 10-31-2007 11:22 AM