Analog Output

[seascan]

Hi.  Can anyone recommend a way to amplify the current that is output from a DAQ? 

I'm using NI 9263 with a maximum output of 1ma/Ch.  I need to drive a valve that has a higher current... The valve I need to drive is controlled with 0-10V, 1.2A.

Is there something I can buy to do this?

Thanks.

terry

[seascan]

I found the ULN-2003 Chip that would appear to work.  I can create the 0-12V, 1.2A output by creating a PWM signal to the chip. 

Does this sound reasonable?

[PBP]

Are you working with control valve or ON-OFF valve?

[seascan]

It's a control valve... so I guess the ULN2003 won't work -- unless I do PWM.

Any other ideas?

[myle00]

A simple transistor should be able to do this. The input to the transistor is the DAQ output and the load is the valve: http://www.rason.org/Projects/transwit/transwit.htm What kind of valve is it? Because you might have to worry about protecting the circuit from the valve.

Edit: didin't realize it wasn't a ON/OFF valve. What kind of signal does the valve expect?

[seascan]

myle,

Wouldn't that just be an on/off?  Or will the output voltage vary proportionally with the input voltage?

Thanks.

EDIT:  Too funny... perhaps we were both editing about the same time!

[myle00]

Take a look at these high current amplifiers: http://www.analog.com/en/high-speed-op-amps/high-output-current-amplifiers/products/index.html http://www.ti.com/product/opa561&lpos=See_Also_Container&lid=Alternative_Devices they all seem to be surface mount though.

So a control valve requires a variable inout? Can you point me to the specs of such a valve?

Matt

[seascan]

Hi Matt.  Here is one of the options I am looking at:  http://www.asconumatics.eu/images/site/upload/_en/pdf1/01029gb.pdf

This one take a 0-12V PWM signal so I can use the transitor in this application.  I am just trying to figure out, for my own education, how to increase the current coming out of a daq with a proportional voltage.  For instace, my DAQ puts out 0-10V, 1 mA and I would like to output 0-10V, 1A.

Thanks Again,

Terry

[myle00]

To increase the current from 2ma to say 1A I'd use a current amplifier like the OPA561 I linked above with a gain of one. The input and output voltage are the same but the output current can be much higher.

Matt

[johnsold]

Another way to a high current variable output (up to 1.5 A) is to use an adjustable linear voltage regulator such as the LM317.  The output of the regulator is 1.25 V higher than the voltage at the Adjust terminal.  The current at the Adjust terminal is ~50 uA. The disadvantage is that you cannot easily go to zero volts at the output (1.25 V minimum for 0 V at the Adjust terminal).

Lynn