What are some GPIB-Programming tips?
The CSA8000 and TDS8000 instruments use a pipelined architecture for data acquisition and control and query commands. As a result, care must be exercised to ensure that the results returned from data or measurement queries are what were expected.
A number of methods exist to flush the acquisition and control queues in these instruments and thereby guarantee the expected results. A few of these are listed as programming tips below:
- Stop acquisitions prior to changing measurement definitions. Failure to clear the results pipeline in this situation could lead to the unexpected result of the value of the prior measurement being returned on a subsequent measurement query.
- Be sure to set up the instrument to Stop After Acquisitions = 1 if you need to guarantee that you have acquired a new waveform. You do this using the following sequence of commands:
- ACQuire:STOPAfter:CONDition ACQWfms
- ACQuire:STOPAfter:COUNt 1
- Be sure to wait until the acquisition is complete by using any of the synchronization commands (*OPC, *OPC? *WAI, and BUSY?)
The above actions are required because the amount of time required to acquire a complete waveform depends on a variety of factors: the periodic rate of the trigger signal; the specified record length; whether averaging and/or FrameScan acquisition is turned on (and if so how many acquisitions must be averaged); the requested Trigger Holdoff; and so on.
- Be sure to include at least 100 ms of delay in the loop that queries instrument status when synchronizing your test procedure to the instrument (using a BUSY? Query, for example). If you do not set sufficient time between status queries, the instrument will have very little time to acquire waveforms and process data.
Be sure to wait for the time listed below after sending each of the following commands before querying for any results that depend the command sent:
- CH:FILTer:VALue 6 seconds
- CH:BANdwidth:VALue 6 seconds
- SAVe:WAVEform 3 seconds These are pessimistic values over all (including old) SW versions. Please read your release notes for more up-to-date values.
Also see current release notes for up to date information.
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