wind speed sensor

[dromar2222]

Hello All,

I have a wind speed sensor and I want to connect it with the cdaq assistant...

air speed range : 0 20 m/s
output signal : 4 20 mA

I only have the NI 9205 card which needs a voltage as input.

My question is if I can connect a resistor to the output of the sensor to transform the ampere to voltage.
This can be read the signal by the NI 9205 card.

Or is it impossible?

any help please !

[santo_13]

If you add an external resistor to convert the 4-20mA signal into voltage, NI 9205 can read the voltage

[dromar2222]

first of all Thank you for your feedback.

I have already done it. But an illogical result appears.

I chose the resistance by the relation: (U=RI) I max is 20 mA (sensor) and U max is 10 V (card NI 9205) so R max is 500 ohms ... I have a resistance of 470 ohms.

the problems that appear :
how can I convert the unit in this case? 
and I find that the sensor displays a voltage of 10V in spite of the absence of the wind

[RTSLVU]

A link to the sensors' specifications or data sheet would help immensely here...

But in general sensors like this need a "burden resistor" to use them as a voltage output instead of a current output.

It is just Ohms Law to some extent, but the sensor response may not be linear under all burden resistor values.

[GerdW]

Hi dromar,

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@dromar2222 wrote:

I chose the resistance by the relation: (U=RI) I max is 20 mA (sensor) and U max is 10 V (card NI 9205) so R max is 500 ohms ... I have a resistance of 470 ohms.

the problems that appear :
how can I convert the unit in this case?

---

Apply Ohm's law!

4mA*470Ohm=1.88V, 20mA*470Ohm=9.40V.

So the scaling uses 1.88V and 9.40V as X values for the same Y values as would apply to 4mA and 20mA…

---

@dromar2222 wrote:

and I find that the sensor displays a voltage of 10V in spite of the absence of the wind

---

Maybe a wiring issue.

You didn''t attach an electronic schematics nor a datasheet of your sensor…

[dromar2222]

I am so very grateful for your time and your help