how to convert square waves to a physical data

[johnsold]

Power supply ground generally connects to AI Ground on the DAQ device.

Lynn

[sgirgin]

i am sending my DAQ in the attechment.considering that i have analog input where is the ground i cannot find it

[sgirgin]

Voltage difference between + and third pin is zero.Does it mean the third pin is ground?

[johnsold]

Unplug the power supply from the mains. Wait a few minutes for any capacitors to completely discharge. Then measure the resistance between the pins. Also measure the resistance between the pins and the grounding electrode on the mains connector and to any metalic parts on the chassis or cabinet. Thise measurements should help to identify the ground connection of the power supply.

AI GND is fourth screw terminal from the bottom on the left column in the image you posted.

Lynn

[sgirgin]

as far as i know pin gorund means negative pin.if so i know which one is negative.then i will try to connect with ai ground screw pin in daq

[sgirgin]

http://www.instructables.com/id/Crystal-cMoy-Free-Form-Headphone-Amplifier/step4/Wiring-the-Power-Ja...

i have exactly this one 

[johnsold]

On that jack two of the pins are connected together.  It looks like you could connect the - pin to AI Gnd.

Lynn

[sgirgin]

Do i need to connect resistance seems it is reading current

[johnsold]

No.  It is swtiching the voltage. The current values are limits.  If the external circuit (the DAQ analog input in your case) draws more current than those limits, the sensor will not work or might be damaged. Your DAQ inputs are very high impedance and will draw almost no current, so thst is not a problem.

Recall that I pointed out the DAQ voltage limit of 11 volts. If the power supply voltage is higher than 11 volts, damage to the DAQ inputs could occur.

Lynn

[sgirgin]

But what can be done if the sensor supply voltage is 24V for my pressure sensor.

In DAQ datasheet it says up to 25V