Connect sensor open collector output to NI USB-6

[Vanessa86]

Good morning Labviewers,

I need to read a frequency (voltage pulse) signal with my NI USB-6229. I already have prepared a vi to do this, but now I'm struggling on how to connect the sensor to it.

My sensor is a Bukert flowmeter 8030 - SE30. The supply voltage needed is 24V and the output I'm using is NPN 0,2 - 36V, open collector.

To measure this signal, I'm using a DAQ NI USB-6229 which maximum input voltage is +10V.

I measured the voltage output (or what I think it's the output)  from the sensor and it was 22V, which I can't connect to the card directly.

I've read about using the +5V output from the same card to the open collector, but I'm not sure how to do it.

Can someone help me with this matter? I really need to test this asap.

Thanks in advance!

Vanessa

[crossrulz · Accepted solution]

The first half of this article might help you: How Do I Configure My NI Device to Be Open-Drain (Open Collector) or Push-Pull (Active Drive)?

But the short of it is that you use a pull up resistor to the 5V and wire it to the NPN output and your DAQ input.

[Vanessa86]

Hi crossrulz,

Thanks for your answer.

Do you know what value of this pull-up resistor should I use?

Thanx.

Vanessa

[crossrulz]

It really depends on how much current your open collector will sink.  I usually go with somewhere between 10k and 100k.  I think many of the NI DIO boards have a 47k.

[Vanessa86]

Thank you very much crossrulz. I've connected the 5V output from the DAQ to a 9 kOhm resistor, then the sensor NPN output, and then this two to the digital signal input. It's working smoothly!

Regards,

Vanessa