lecroy offset

[Aurélien]

Hi,

i need to do measurement on the top envellop  of a signal (between 100mV and 2V peak to peak). The signal I measure on the envellop is around 10mV. So to have a better precision I apply a vertical range of 20mV/div, and have to apply a vertical offset.

The vertical offset will depend of the voltage peak to peak of the signal. My problem is that I don t manage to understand the relation between the vertical offset value I send to the "Configure Channel.vi" and the value applied by the scope.

Is anyone can help me?

Thanks.

Best regards.

A.R.

[alanjb]

Hi A.R,

Alan from LeCroy Tech Support here...  What model scope are you using, and which driver? (Configure Channel is a VI that is used in several drivers.)

One problem could be that you are attempting to set an offset value that is too big for the volts/div setting.  In this case, the scope will coerce the offset to the maximum allowed value.

One other question... Are you using a probe?  If so, what model number?

Thanks,

Alan

[Aurélien]

Hi Alan.

I use a wave surfer 44XS, with the wave series driver ( i don't know the version).

I have seen that the offset applied on scope depend on the value peak to peak of my signal.

For example if I have a signal of 0.74 Vpp, and that i applied an offset of -3.68V, the offset on scope is -0.368V.

And if I have a signal of 0.45 Vpp, and that i applied an offset of -3.68V, the offset on scope is -0.736V.

Thanks for your help.

Regards.

AR

[Aurélien]

Sorry i forgot to answer on the question of the probe.

I don t use probe i directly do the measurement on an Antenna connected BNC 50ohms.

Thanks.

AR.

[alanjb]

Hi A.R.

I'm unable to reproduce the issue...  Let's make sure you have the latest version of the driver; this can be found by opening the HTML readme file that is in the folder for the driver under the instr.lib folder.  I know that the latest version includes the following fix:  "lcwave Configure Channel: Added coupling options AC and DC to support probes, moved VDIV ahead of OFST for ruggedness"   (The same fix is in the "LeCroy Wave Series" driver, which has the exact same code as "lcwave"). 

Best Regards, Alan

[Aurélien]

Hi Alan,

I think that I have found the solution.

The error occured when I made an update on the vertical coupling and on the offset on the same time.

So If I first make the update on vertical coupling and after make the update on the offset it works.

Thanks for your help.

Best regards.

A.R