用34401A测100uA的交流小电流的方法
大家知道34401A有4个直流电流测量量程：10mA，100mA，1A，3A，却只有两个交流电流量程：1A和3A，如果想测低于10mA以下的交流电流，用1A 量程准确度就大大下降了（交流1A指标：0.1%读书+0.04%量程，在测<5%量程的小电流时还需+0.1%l量程附加误差）。
下面介绍给大家一个不需要增加成本却能使34401A具有10mA的交流电流量程的方法，而且技术指标能达到交流1A量程的指标。
方法：通过接口（GPIB）给34401A发送“DIAG: POKE 25,0,1 ”命令激活交流10mA量程后，就可以通过前面板或程序来测量了。
为什麽要将这功能隐藏起来, 要靠GPIB才能激活出来? good!
ag网站说明：
Is there a way to measure low-level ac current using the Agilent 34401A?
Yes. The lowest specified measurement on the 1 A ac current range is 1% of the range, or 10 mA (see footnote 4 in the Data Sheet). However, there is an undocumented 10 mA range on which you can measure down to 100 uA. To enable the 10 mA ac current range, send the following command over the remote interface:
DIAG:POKE 25,0,1
Once enabled, you can access the range from the Agilent 34401A front panel or over the remote interface bus. It will typically perform to the 1 A range specifications. The 10 mA range is tested on the production line.
Why isn't the 10 mA ac current range included as one of the standard ranges for the Agilent 34401A? It is because adding a 100 mA range would have added significant cost to the instrument for a measurement that is infrequently used, and implementing the 10 mA range without the 100 mA range would require the long explanation, that you are currently reading. Therefore the decision was made to document only the 1 A and 3 A ranges.
The increased cost is due to the addition of a precision shunt resistor. The selection of shunt resistors for the rest of the design only required .1Ω and 5Ω. With a 100 mA input, the shunt voltage would be either (.1 * .1) 10 mVAC or (.1*5) .5 VAC. The 5Ω shunt cannot be used because a signal wih a crest factor of 5 would generate a burden voltage of 2.5V, and the front-end protection would clamp the volatage to 2 Volts. This leaves the .1Ω shunt; however, at 10% of full scale (10 mA), this generates only 1 mVAC, which has poor accuracy on the 100 mVAC input.
If you ever want to disable this range the command to do it is:
DIAG:POKE 25,0,0
Re:用34401A測100uA的交流小電流的方法
感謝LZ分享, 剛測試一下, 發送指令之後就可以開啟mAAC的檔位, 不過, "DIAG:POKE 25,0,1"指令中的冒號後面不能有空格.attachment/photo/Mon_1102/218_74ba129674952579fee7d38ac7e86.jpg 好经验。 很好，楼主不提，我都忘记了。这个功能，自从我的34401A多年前到手后，就开启了。但好像真没有正式用过。
刚才开机试验了一下，10mA交流档，不接表笔，读数00.001,2 摸都没摸过34401A的掩面路过！ 引用第6楼大大大老虎于2011-02-0414:54发表的:
摸都没摸过34401A的掩面路过！ images/back.gif
嘿嘿，别急，会摸着的。 争取摸4708,3458 俺只看过34401的图片，但俺也谢谢楼主。 想知道，没有GPIB 如何打开这个功能？ 学习了，谢谢，等有了34401立马试试 见识了 34410A如何搞？ 20多年测电流的情况还真没几次。 一般只用直流的飘过 感谢分享。。。。 用串口连接机器，激活就可以了。
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