Agilent 3458A DMM波形捕获

我正在尝试使用3458A来实时捕获包含从​​0到4v的周期性斜坡的数据。
我希望在触发后实时捕获FIRST斜坡上的所有数据。
我有一个连接到3458的函数发生器，提供这个波形。
我想捕获并将电压值存储到阵列中以进行后期处理。
我正在使用HP3458A labview驱动程序附带的Labview Application Read Waveform.vi。
使用默认的“样本数”和“采样率”，我得到了预期的数据显示（参见goodwaveform.jpg）。
采样率为50Hz（50个样本/秒）的100个样本捕获2秒的波形。
波形为500mS斜坡，占空比为50％。
这很好。
但是我想仅收集波形的500mS段上的数据，似乎合乎逻辑的是我应该能够将采样率设置为1000个样本/秒（每个样本1ms）并读取500个样本以查看500ms的部分
波形。
显然我错了，因为第二个屏幕截图显示了这些设置的结果。
看起来采样率接近~72个样本/秒而不是期望的1000个样本/秒。
我究竟做错了什么？
附上VI。
。
badwaveform.JPG110.3 KBgoodwaveform.JPG106.9 KB



     以下为原文

  I’m trying to use the 3458A to do a real-time capture of the data comprising a periodic ramp that goes from 0 to 4v. I want to do this in REAL TIME capturing all data on the FIRST ramp after the trigger.  I have a function generator connected to the 3458 delivering this waveform. I want to capture and store the voltage values into an array for post processing. I’m using the Labview Application Read Waveform.vi that comes with the HP3458A Labview driver. Using the default “number of samples” and “sampling rate” I get the expected data display (see goodwaveform.jpg) . 100 samples at the sampling rate of 50Hz (50 samples/sec) captures 2 seconds of the waveform. The waveform is a 500mS ramp with 50% duty cycle. This is good.  However I want to gather data ONLY on a 500mS segment of the waveform, and it seems logical that I should be able to set the sampling rate to 1000 samples/sec (1ms per sample) and read 500 samples to view a 500ms section of the waveform. Obviously I’m wrong because the second screenshot shows the results of those settings. It appears the sampling rate is closer to ~72 samples/sec instead of the desired 1000 samples/sec. What am I doing wrong? VI attached.

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附件

• applicationreadwaveform.vi16.9 KB
• badwaveform.JPG110.3 KB
• goodwaveform.JPG106.9 KB