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controlling pressure regulator with U6


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5 replies to this topic

#1 moeller

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Posted 26 February 2013 - 02:32 AM

Hi, I'm pretty new at this, so I guess this might be a simple question to answer. I just bought a U6 to control my pressure regulator, but I can't make it work. Is it not possible or am I just doing something wrong. the pressure regulator that I am using is from Pneumax and the model I have is called: 171E2N.T.D.0009. I have attached thetechnical datasheet for the regulator. My thoughts was to control it with an inputsignal of 0-5V with the DAC terminal, but somehow nothing happens when i connect it. The only pins that I have connected is the 24V supply, GND and input signal. I hope someone out there can give me and answer. best regards, Moeller

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#2 LabJack Support

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Posted 26 February 2013 - 08:35 AM

So you have: PowerSupply+ to regulator SUPPLY. PowerSupply- to regulator GND. U6 DAC0 to regulator ANALOG INPUT. You also need: U6 GND to regulator GND. (DAC0 needs to be referred to the same ground as ANALOG INPUT on the regulator) Use a DMM to check your signal voltage. You want to measure the voltage at the regulator from ANALOG INPUT to GND. Also, it looks like you need to go through the setup screens on the regulator and set various parameters so it will be controlled by the 0-5V analog signal.

#3 moeller

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Posted 26 February 2013 - 09:12 AM

Thank you for your reply. I have connected the terminals as you said, and it is now regulating the pressure. I don't know if this i common, but the regulator displays a little lower output than what the setpoint is. E.g. setpoint: 2V, output voltage: 1.8V. is that normal? best regards, Moeller

#4 LabJack Support

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Posted 26 February 2013 - 12:38 PM

DAC0 has 50 ohms of source impedance, and the regulator says it has 10 kohms of load impedance. So if you set DAC0 to 2.0 volts, you expect about 200uA of current which would drop about 10mV across the 50 ohms so you still expect about 1.99 at the load. So, it does seem lower than expected. You can use another analog input to measure the voltage at the load. Another test is to measure the DAC0 voltage with a DMM. Is it 2.0V when floating, but drops to 1.8V when connected to the load?

#5 moeller

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Posted 26 February 2013 - 01:10 PM

I will try measuring the voltage drop with my DMM. How do you get to a drop of 10mV? what equation are you using? input voltage is around 12,5% higher than what the output is showing.. best regards, Moeller

#6 LabJack Support

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Posted 26 February 2013 - 02:09 PM

How do you get to a drop of 10mV? what equation are you using?

Using Ohm's law: I=V/R

I = V/R = 2.0 / (10000 + 50) = 200uA

V dropped through internal resistance = I * R = 0.0002 * 50 = 0.010 volts


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