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[问答]

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

以上来自于谷歌翻译


     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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回帖(5)

杨梅

2018-12-4 16:26:06
这个可能很难。
3458A的Labview驱动程序是为了舒适而不是速度而设计的。
如果我的记忆服务正确,那么软件会不断地查询仪器以查看数据是否可用,这会大大减慢速度,而且我很确定他们使用的是OFORMAT和MFORMAT ASCII,这也是一种较慢的方式来发送数据。
总线。
您可能不得不使用签证写入和读取来编写自定义程序,而不是驱动程序来获得您想要的速度。
如果我有时间,我会明白是否可以明天鞭打一些东西,至少是为了让你前进。
您是否反对将数据写入内存,然后将其拉出来?
我正在考虑采用这条路线,以防止数据丢失,如果Labview无法跟上采样率。
我不知道这是否有必要,直到我尝试,但我想我会先花时间在这上面。
从用户角度来看,这是一种较慢的方式,但这样就可以将数据写入内存而无需PC /软件开销。

以上来自于谷歌翻译


     以下为原文

  This one may be tough.  Labview drivers for the 3458A are built for comfort, not for speed.  If my memory serves me correct the software is constanly polling the instrument to see if data is available, which greatly slows things down, and I'm pretty sure they use OFORMAT and MFORMAT ASCII, which again is a slower way to send data over the bus. 


You're probably going to have to write a custom program using visa write and read as opposed to the driver to get the speeds you want.  If I have time, I will see if I can whip something up tomorrow, at least to get you going.  

Are you opposed to writing the data to memory, then pulling it out?  I was thinking of going this route just to prevent data loss if Labview can't keep up with the sample rate.  I won't know if this is necessary until I try it, but I thought I would ask before I spend time on this.  This is a slower way to go about it from the user perspective, but this way you are writing the data to memory without PC/software overhead.
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向珍

2018-12-4 16:37:53

谢谢!
我会尽我所能的帮助。

以上来自于谷歌翻译


     以下为原文

  Thank you! I'll take all the help I can get.
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杨梅

2018-12-4 16:55:29

不幸的是,我今天没有时间研究这个问题。
我要出去约一周了。
希望其他一些论坛用户可以跳进去帮忙。
抱歉

以上来自于谷歌翻译


     以下为原文

  Unfortunately I didn't have time to work on this today.  I'm going to be out for about week.  Hopefully some other forum user can jump in and help out.

Sorry
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向珍

2018-12-4 17:08:35

仍然需要帮助。
任何接受者?

以上来自于谷歌翻译


     以下为原文

  Still need help with this. Any takers?
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