Setting trigger on Agilent 54845A Infiniium oscilloscope

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Anyone know how to set the trigger sensitivity from Labview 7.1 on the Agilent 54845A Infiniium oscilloscope. I have the hp548xxA driver which has VI's for setting just about everything else...
I can manually set the sensitivity to 'high' but running any Labview programs sets it back to 'low'.

Help?

[Dennis_Knutson]

What are you using to set 'sensitivity'? The front panel has a Level setting knob and the trigger level can be set with HP548xx Configure Edge Trigger Source.

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Yeah I can control the trigger level ok using the HP548xx Configure Edge Trigger Source. On the front panel of the scope there is also a 'Sensitivity' button that toggles between 'High' and 'Low' .... I'm not even exactly sure what this does, but I know that it needs to be set to 'high' in order to capture the waveforms I am looking at. There does not seem to be a VI that controls this function...

[Dennis_Knutson]

I have an older model Infinium and I don't have that button. The service manual for the 54845A doesn't show it either (see bleow) and of course Agilent no longer has the user manual on line because it's obsolete.

If you do have the user manual, you might want to check to see what the button does. If the driver doesn't contain the function, it's just possible is was missed by the programmer who wrote the driver. There might actually be a command that you can send but the first step is to determine what the button does exactly and I'm afraid I can't help much unless you have an electronic copy of the user manual that you can post.

Message Edited by Dennis Knutson on 02-20-2007 04:39 PM

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My apologies. I am actually using the 54854A Infiniium. Bit of a typo. I should have double checked that before I posted!

I think I have figured it out anyway. The sensitivity setting has to do with hysteresis. A low sensitivity adds hysteresis to the trigger circuit, while high sensitivty lowers it so that you can trigger on higher frequency waveforms.

The conf trigger.vi has a hysteresis control that allows you to set 'Normal' or 'Noise reject'... turns out that normal = low sensitivty and nose reject = high sensitivity

Just a bit confusing with the different terminology.

Thankyou for your help

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False alarm.

I thought that hysteresis setting would work for sure... however it does not seem to change the sensitivity setting. Is there a certain order I am supposed to use the Conf Trigger.vi in? I am using it to change the sweep setting from 'auto' to 'triggered' and that seems to work. Changing the hysteresis setting doesnt seem to change anything.

[Dennis_Knutson]

I guess the first you can try is to see whether the hysteris command actually does do the same thing as the sensitivity button. You can go into MAX and enter the query "Hyst?" (without the quotes). I'm guessing that is the correct syntax as I don't have the manual for this model scope. Manually press the button and see if the results from the query change. If the results do change, then you might want to single step through your program and when paused, go to the query and see if the status of the hysterisis setting has changed from when it was programmed. It's possible that some other command that is sent will change some other setting.

If the hysterisis status does not change when you manually press the button, then one handly thing is the *LRN? query. This will return the current setup. It's going to be a fairly long string and going through it to look for differences can be tedious. I've used a diff tool to make it easier to spot what changes. With instruments that have the *LRN? command, I've even cheated and not written a driver on occasion. You can manually set up an instrument, do the *LRN?, save the results, and later when you want to program the instrument, just send the saved string back. When you only need to setup an instrument once, this technique works okay.

Hope this helps.

[tooms]

Thanks Dennis.

Turns out the 'conf trigger.vi' was entering the wrong string when the hysteresis was changed. The scope didn't recognise it and so it just set it to the default value. Now that problem is solved a new one has popped up in the 'conf channel.vi' where I cannot change the vertical scale of the scope.

When I try and run just this on its own I get a message "Unknown header" on the scope. I am assuming this means that the vi is again entering an incorrect string? I have managed to get the programming guide from the Agilent website so I guess it is just a matter of going through the 'conf channel.vi' and making sure it is using the correct syntax.