Agilent 33220A DC offset + OPAMP offset is not as it should be when i use labview

[LTBALAZS]

Hi there,
The output of Agilent 33220A can be maximum +5V. I need more than +5V, so i made a simple DC amlifier circuit connected to the 50ohms output of the instrument. (I need 2*Vin)

When i set manually the output of the intrument as "High Z" then all is fine.
Then amplification works as desired.: I tried 0...4V input->0...8V output.

Then I tried to set output in the Labview as follows:
Offset voltage = 1V.

DC amplifier board disconnected:
When I connect my voltmeter to the output of the function generator i measure the same as I configured in labview: 1V

DC amplifier board connected:
When I connect my amplifier circuit to the 50 ohms output of functioin generator,  then i get some strange amplification value. 2.59V
Measurement voltage should be 2V.

I tested amplifier circuit and it works fine without labview.
In short I can't get higher than 5V in the output of amplifier circuit no matter what i do in labview, but when i set things manually all is fine.

Have you got any ideas why this happens?

[cstorey]

I suspect the "Initialize.vi" resets the instrument to default 50Ohms out, not "High Z" mode. Usually by default an instrument driver initialize VI will do a hard reset to factory default settings.  In your picture you haven't supplied true or false to the reset terminal so its doing whatever is the default.

Look for a VI that comes with the driver that specifically sets it to "High Z" mode or physcailly set it to High Z then make sure the initialize VI does not reset the instrument.  Then run your tests again.

Craig

[Minions]

Here is the excerpt from the manual,

OUTPut:LOAD {<ohms>|INFinity|MINimum|MAXimum}

OUTPut:LOAD? [MINimum|MAXimum]

Select the desired output termination (i.e., the impedance of the load attached to the output of the Agilent 33220A). The specified value is used for amplitude, offset, and high/low level settings. You can set the load to any value from 1Ω to 10 kΩ. MIN selects 1Ω. MAX selects 10 kΩ. INF sets the output termination to “high impedance” (>10 kΩ) . The default is 50Ω. The :LOAD? query returns the current load setting in ohms or “9.9E+37”

(for “high impedance”).

For your needs, you can add this after your initialization by using a VISA write with the string entry of:

OUTP:LOAD INF\n