GPIB USB HS- syncronize Bus

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May I know Can I use GPIB USB HS controller to syncronize two DMM.

Regards

Wije

[Dennis_Knutson]

With the GPIB bus, you can issue a GET (Group Execute Trigger) so you can initiate a measurement at the same time.

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Thanks for reply. I tried initialize and take readings from two DMM simultaniously. But DMM were initialized to measurements one by one. How I configure GET command?

[Dennis_Knutson]

On the 488.2 palette, you have the Trigger function and the Trigger List functions. The VISA GPIB Command function allows you to send a GET I believe. Before you issue the GET, you have to configure the instruments for a bus trigger source and after they have triggered, you will read them sequentially.

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Thanks for reply. I cannot understand the reply. I use GPIB USB controleer to syncronize two DMM (HP3458A) to read current and voltage signal simultaneously using externel Trig souce (PLL) to calculate power. Always multimeters initialize with time delay. This time delay effected to the measurements. How I solve this problem. Please help me

Best regards

wije

[Dennis_Knutson]

Well, you were asking about GPIB bus synchronization, not external triggers. The external trigger should be providing the same functionality and with an external trigger, the GPIB bus is not involved except when you do a query to see if the trigger has occured. If you have a substantial delay between one instrument triggering and the other, it could be the way you have configured them. What programming language are you using? Are you using a driver from NI? Can you post the code?

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I use Lab View 7,1 and NI drivers for HP 3458A. I want to syncronize Two HP 3458A . First I initialise DMMs and then Trig Arm with Ext source. And then followed Event trig with level triggering and sample event. I noticed at the initialize stage DMMs are initialize with time delay. I need to start measurement at same time. I am not sure GPIB USB driver helps this funtion. How I do syncronize two DMM with or without external triggering.

[Dennis_Knutson]

I really don't understand your comment about 'initialize with time delay'. To me, initialize means preparing both instruments for a specific type of measurement and arming them for the external trigger. You do this one instrument at a time. When both instruments are initialized, they should be waiting for the external trigger event. When the trigger event occurs, both instruments will acquire at the same time. I don't have the 7.1 driver and the 8.5 is probably a lot different. There is a function there called Wait for Acquisition Complete. I suspect this should be called before you attempt to do a fetch.

As I said, you can post your code for someone to look at. Can you also provide some information about the external trigger?

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The external trigger is 2kHz PLL  square wave signal and Initialized mean prepaire DMM for wave form digitising. When run the programe 1st step is inititialize DMM for measurement. This event should occur at same time. But it happen one by one. That is the problem. I attached here with rhe Block diagram.

Thanks

Wije

[Sputnikrent]

Hi Wije,

I'm having trouble understanding, why do you need to initialize DMMs for measurement at the same time, if you have an external trigger that will be triggering the measuements?