LeCroy Wavemaster 8600 change measurement range

[wcm]

Hello,

I am currently working on a piece of software that need to use VISA to connect to a LeCroy wavemaster oscilloscope. This i have working, but now i am finetuning. What i want to do is change the y axis to adapt to previous received waveforms. This because i measure the signal as precise as possible and not have measurement points wasted. a quick paint drawing:

The red line is the signal (all signals look like this) and the black border is the default maximum measurement range fom the scope. What i had in mind was to change te range to the blue lines. If for instance i have 100 measurement points, i can better use them in a maximum range of -2 to 2 Volts then -10 tot 10 Volts.

My question is, how can i adapt the range? I use Labview 8.2 with the Lecroy developt Labview drivers. Do i need to use the lcwave Configure Channel.vi for that and change the Vertical range settings (if so, is the default value (10) top-top?)? I am not certain if this is the correct way and since i can only test 1 hour per week if it is a slow week, in need to make this without testing possibilities for some time. 

[NathanT]

Hello WCM,

      I looked through the LeCroy Wave Series instrument driver and did not see any settings for Autoranging.  This means that you can either just use a range that you know will be larger that your signal, OR have your application check the range of the measurements that it is acquiring from the scope and then programmatically adjust the range (with Configure Channel).

      Something to consider with the second option is that re-configuring the range while acquiring might cause you to lose some data points.

Let us know what you decide and how you choose to implement it.

Cheers,

NathanT

[wcm]

Hello,

Thanx for the reply. The waveform i will be receiving is generated every 3 seconds. After i receive the waveform from the scope, i already process it in another loop (Min, Max, Statistics, duration, export). My plan is after receiving 5 waveforms to find the highest peak in the five, add 20% overhead and use that for the next measurment. And after that one find the maximum of the six waveforms and so on. This way the measurment will be more precise because delta y on the y-axis will be lower.

[alanjb]

Hi WCM,

Alan from LeCroy Tech Support here...  Configure Channel is indeed the VI to use to configure the vertical scale, and the Vertical Range control corresponds to the full scale volage (= volts/div  * 8).

Instead of transferring entire waveforms and measuring an average pk-pk value off-line, why not use the scope's ability to make these measurements?  For example, you can setup P1 to measure pk-pk, then issue the VIs to Initiate a trigger and Wait for Acquisition Complete 5 times in order to take 5 triggers (or 50, or 500....)  Then call Read Measurements (Px Statistics).vi to find out the mean value of the peak-to-peak measurements.  Then add your 20% overhead and call Configure Channel.vi. 

Regarding Nathan's comments  (Hi Nathan, how've you been?).... There is an AutoSetup VI, but it looks like it isn't fully implemented. You can send the command Cx:ASET FIND using Write.vi to autorange Cx (x = 1, 2, 3, 4).  Your success in autoranging will depend on whether your signal has a well-defined range from sweep to sweep. Abou reconfiguring while acquiring... I would recommend issueing configuration commands while the scope is stopped in order to avoid any confusion.  (Typically, when using the scope via remote control, you will want to have the PC control the scope's triggering via the Initiate VI (or the Read Waveform VI, which calls Initiate.)

Don't hesitate to contact me if you have any questions!

Best Regards,
Alan