When I send a 5v from the DAQ, the voltmeter shows 5V, but when i connect a "normally open valve" from parker to the DAQ, the voltage automatically decreases to .14 V. It seems like it is being grounded. Why is this happening?

[nsatpute]

We are sending 5v to the DAQ using a voltage generator. We hook this up to a voltmeter and we see 5V. When we connect the voltage generator to a "normally open valve" from parker, the voltmeter shows .14V. It seems that when we connect both wires from the valve to the voltage generator, the wires are acting as a ground. We wish to control the voltage that flows to the valve through Labview. We checked the wires of the valve and they are working fine becuase if we send a constant 5V from the DAQ and grounded it, the voltmeter shows 5V. Does anyone know why the wires are acting as a ground and dropping the voltage to .14V?

[Dennis_Knutson]

You probably need a driver to provide the required current. You failed to mention the actual DAQ device but most cannot source enough for something like a valve. The specs of the valve should tell you how much is required and the specs of the DAQ device will tell you how much it can provide. This is a common problem for beginners with no electronics background. A common driver is the ULN200X type.

[nsatpute]

Our DAQ is NI USB 6259. The valve only requires  a max of 5V and our DAQ does provide up to 5V. However, after connecting the valve to the DAQ, the voltage drops to almost 0. We are assuming that the wires somehow act as a ground, but we are not sure if this is the case. 

[crossrulz · Accepted solution]

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@nsatpute wrote:

Our DAQ is NI USB 6259. The valve only requires  a max of 5V and our DAQ does provide up to 5V. However, after connecting the valve to the DAQ, the voltage drops to almost 0. We are assuming that the wires somehow act as a ground, but we are not sure if this is the case. 

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The issue here is not how much voltage the valve wants, it is the current the valve needs.  The 6259 can only put out 5mA through an analog output.  Your valve very likely needs a lot more than that.  So you need to add in an amplifier circuit that can supply more current to operate your valve.