HP4275A bias voltage

[HortenseD]

Hi,

I'm actually using a HP4275A to make Capacitance Voltage plotter with Labview.

I've downloaded the ni driver to control the meter and it works.

Now, I'd like to control voltage (DC intern BIAS) of the meter with Labview to do sweep DC Bias voltage measurements.

I don't know how I should build my VI in order to control intern BIAS of my meter.

I succeeded in communicate  the BIAS command with NI Communicator.

Has somebody ever done such a thing with a HP4275A?

I didn't find VI  for this instruments which makes it.

Any help will be welcome as I'm a novice in Labview. 

Thanks

Hortense

[Dennis_Knutson]

You've got a pretty lousy driver. Two of the front panel controls are not wired to the connector pane and the instrument address is a block diagram constant. If no one provides you with a better driver, you will first need to find the programming manual for the instrument and determine what the command is to set the bias voltage. Then, you can either add that to the VI you've got or use the Instrument I/O Assistant to write them. You should first experiment with sending the commands in MAX before writing any code.

[HortenseD]

I have communicated BIAS command to the HP via MAX, and it works. I plugged a voltmeter between the high and low connections of the meter and it delivered the voltage I commanded.

Now, my problem is I want to send a sweep voltage to the meter and for each value of the voltage remote the capacitance value measured.

The VI, I use, can't make it and I don't how I can introduced voltage command in the existing VI.

I suppose I should use GPIB write to send the command to the meter, however I should put this command in a loop as the voltage varies with a specified step.

The major problem is I'm a real novice in Labview and it's not easy for me. That's why I'm lokking for some existing VI.

I found a VI corresponding to this kind of measurements (with another equipment, a HP4284) but many VIs used in the principal one are missed.

So, if you have an idea to help me that will be great !

Thanks

Hortense

[Dennis_Knutson]

The code you need is not all that hard to create. You can use the Format Into String to create the command for the instrument. Then put it inside a while loop with a shift register. The initial voltage is wired to the shift register and in each loop iteration, you add the step value. The applied value is compared to the stop value to determine when to stop the while loop. You could also use a for loop by calculating the number of iterations from start/stop and increment. Here's a picture the shows the basics of what you have to do. You will have to add the measurement function.

Message Edited by Dennis Knutson on 05-04-2006 09:39 AM

[rcd152]

what command did you use for the DC Bias? I tried the one on the HP4275A manual: BI100E+01V for a bias of 10V and it didn't work.

[a sunfish]

I meet the problem too.I try the code BI+100E+01V in max ,but can't measure correspond voltage.Is the code wrong?

Who knows tell me please,thanks!

sunfish