fiber optic sensor su19 110 115a 126a vs ni usb 6008

[yanz]

Hi expert.. I am looking for idea or help on my project. I try to get measurement output from mention sensor via ni usb 6008. Actually i am new with ni usb device n still study n searching on internet n ni forums. I found an idea to connect the sensor through aoi but i fail to get any measurement. Is the sensor may connect directly to usb device or need some custom wire diagram between them. Thanks in advance

[johnsold · Accepted solution]

First, it is helpful if you name the manufacturer of the sensor. A part number alone does not mean anything to most of us.  Are you using the Pepperl+Fuchs fiber optic sensor? Even better is to post the datasheet/manual of the sensor or links to them.

The datasheet I found for the Pepperl+Fuchs sensor is not very well written, in my opinion. It appears that the outputs are pulses with amplitudes dependent on the power supply voltage and frequency or timing set by operating mode.  

If that is the device you are using, the only way you have any chance of decoding the outputs with the USB-6008 is to measure them with an analog input and then process the data in software. Depending on the power supply voltage, you will probably need a voltage divider to reduce the sensor output voltage to a level compatible with the DAQ device.  You also will not be able to use the high speed mode of the sensor because the pulse rate exceeds the Nyquist limit. In standard mode you mighte be OK but you can only use one channel of the USB-6008 to stay within the Nyquist limit.

Lynn

[yanz]

You are correct johnsold. I am using that manufacturer sensor. The sensor itself have 4 cables (pigtail) where cable 1 & 3 use for supply (24v from external supply). I just connect cable 4 to analog input of ni usb 6008. I will try set the sensor into standard mode & see if have any measurement recorded.

[Henrik_Volkers · Accepted solution]

As Johnsold alrady stated your output signal is a 24V  digital signal (to sensor GND/ 0V) .... so depending on what you want to measure you need to reduce the voltage output.

So what do you want to do?  And how fast do you expect the signal to change?

To bring the signal down to a secure level I would propose this circuit:

it will limit the output voltage to 2 times the LED voltage , red LEDs have about 1.8V , so you end up with 3.6V pulses you can measure savly with any 6008 input.

As an additional benefit you get a visible indicator 🙂

for slow detection (software timed) use a digital DIO pin

faster is the analog input

for very fast counting you can use the PFI0 counter.

AND VERY IMPORTANT: you need to connect the sensor supply 0V to the 6008 GND, sorry missed that in the diagram.

[johnsold]

Henrik,

Thanks for the detailed explanantion.

Lynn

[Henrik_Volkers]

Lynn, thank you for the Kudo, but did YOU realy need that explanation? 😉
OT: 22h , 29°C ~90%rel. H @ Praha IMEKO conference ..... but tbe beere is good 🙂

[johnsold]

No, but I hope it helps the OP.

Lynn

[yanz]

Thanks a lot Henrik & Johnson.

Looks like details enough info for me to complete my task. Let me try this circuitry on coming Saturday & feedback to you all for the results. Agains, Thanks a lot & pls waiting for my feedback.

[yanz]

Hi Johnsold & Henrik,

I am back for good result.

The idea & diagram provided help me a lot to reduce input voltage pulse & able to measure the pulse on Labview USB 6008.

I just play around the freq. in order to capture perfect pulse.

You may see the pics attachement.

Now, I am going to calculate rpm from the pulse.

Thanks a lot Expert.