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Thread: 34970A Scan and Read time

Permlink Replies: 1 - Pages: 1 - Last Post: May 21, 2012 12:48 PM Last Post By: tomc Threads: [ Previous | Next ]

Posts: 19
Registered: 10/28/11
34970A Scan and Read time
Posted: May 21, 2012 12:36 AM
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I am Using 34970A Data logger,GPIB and VISA COM API in C# language,Now my problem is i have to configure some channels for voltage,temp and humidity measurements and have to read those values,But here i wanted to know scan and reading time of channels,so that i can wait till all channels configured,otherwise i am having problem in programme when i send read command to instrument while it is in scan,also i need more accurate values thats why i am using 6 1/2 resolution.

when i set channel for this resolution,it automatically configuring for Integrated Time PLC and ADV,can u explain me what are this and for what??

Posts: 217
Registered: 01/12/11
Re: 34970A Scan and Read time
Posted: May 21, 2012 12:48 PM   in response to: chadalawada in response to: chadalawada
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If you want to know the actual measurement time, which is the integration time, use the commands to set that time directly in NPLC units. In other words for DCV, use first CONF:VOLT:DC auto,(@<ch_list>) followed by VOLT:NPLC <value>,(@<ch_list>). See the comments in the command reference under the SENS:VOLT:NPLC command for the relationship between resolution and NPLC. NPLC * 20ms gives you the actual measurement time for 50 Hz power lince frequency. The time for the complete measurement operation is longer if autozero and autorange are enabled. Note that there are five different NPLC settings that give you 6 1/2 digits. The longer settings are useful if you have much noise on the signal.

After all the measurements are configured for each channel, you set up the scan list with the ROUT:SCAN (@<ch_list>) command. Each channel can have its own configuration as set up by CONFigure commands for each channel or groups of channels with the same measurement function. The READ? command will then execute a complete scan of all the channels in the scan list. The actual channel configuration happens during the first pass through the scan list. So the second and all subsequent read commands will execute much faster than the first.

The execution time of the READ? command includes both the scanning time and the measurement time. You set the measurement time with the NPLC, autozero, and autorange settings. The scanning time is set by the hardware and is fixed. The READ? will not complete, i.e., return data until all the measurements and the scanning are complete. I hope this answers your questions.

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