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韩凤英

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如何将这些Vcomp和Vrf输出连接到34401A电压输入？

我正在尝试使用带有478A热敏电阻安装座的HP 432A功率计精确测量E4417A功率计的50 MHz / 1mW RF参考输出。我已按照432A的用户指南说明如何在考虑Vcomp和VRF电压的情况下进行精确功率测量。
为此，我有一台安静的34401A DVM。
主要问题是那些Vcomp和VRF值不稳定，即使我已经为仪表制作了粗和细零。所有设备都位于温度稳定的实验室（23 + 1/1摄氏度）。
许多用户指南表示要使用更精确的Agilent 3458A DVM。
34401A对于那些Vcomp和VRF测量仍然是精确的吗？我应该首先考虑一些特殊的如何将432A电表归零以及如何将这些Vcomp和Vrf输出连接到34401A电压输入？
我只有一个DVM，我将Vrf连接到DVM的后输入端，Vcomp连接到前输入连接器，使用BNC电缆，另一端有合适的香蕉连接器。如果有人有这种精确功率测量的实用提示或建议，请告诉我。

以上来自于谷歌翻译


     以下为原文

  I'm trying to measure precisely E4417A power meter's 50 MHz/1mW RF reference output using HP 432A power meter with 478A thermistor mount.
I have followed 432A's user guide note how to make precision power measurement taking account those Vcomp and VRF voltages. I have one
Agilent 34401A DVM for that purpose. Main problem is that those Vcomp and VRF values are not stable even i have made Coarse and Fine zeroes for the meter.
All equipment's locates temperature stable laboratory (23 +/ 1 celsius). Many user guides says to use more precisise Agilent 3458A DVM. Is 34401A still enought precise for those Vcomp and VRF measurements?

Should i take account something special how to zero 432A meter first and how to connect those Vcomp and Vrf output's to 34401A voltage inputs? I have only one DVM where i have connected Vrf to DVM's rear input and Vcomp to front input connectors using BNC cable's where another end has suitable banana connectors.

If someone have practical hints or advices for such a precision power measurements, please let me know.

回帖（4）

冯琳

2019-7-12 07:59:52
我认为连接存在问题 - 您无法同时使用前后DMM输入 - 有一个开关可以设置哪些输入有效。
连接既可以在前面，也可以在后面。电缆应该将432A BNC连接器的中心导线连接到34401A上的一个香蕉插座。
您不要将BNC插孔的接地（外导体）连接到DMM。
您可能需要使用适配器或制作特殊电缆。
我不确定34401A的准确性。
有关E4418B服务指南中程序的不确定性分析：http：//cp.literature.agilent.com/litweb ... -90059.pdft测试程序在第2-17页，更多信息见附录A
和附录C.使用附录C分析来查看DMM准确度是否足够。

以上来自于谷歌翻译


     以下为原文

  I think there is a problem with the connection-

you can't use the front and rear DMM inputs simultaneously - there is a switch to set which inputs are active. Connections are either both in the front, or both in the rear.

the cable should connect the center conductor of the 432A BNC connector to one banana jack on the 34401A. You do not connect the ground (outer conductor) of the BNC jack to the DMM. You will probably need to use adapters or make a special cable.


I am not sure about the accuracy of the 34401A. There is an uncertainty analysis of the procedure in the E4418B service guide:
http://cp.literature.agilent.com/litweb ... -90059.pdf
the test procedure is on page 2-17, and further information is in Appendix A and Appendix C. Use the Appendix C analysis to see if the DMM accuracy is adequate.
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韩凤英

2019-7-12 08:16:19
谢谢。
问题在于连接不良。
是的，当然我必须在DVM上使用这个机械前面板开关，它可以激活前置或读取输入。更好的是，当我将热敏电阻安装归零时，该安装座未连接到DUT的RF输出甚至RF
电源是从它？
我看到奇怪的表现，当为E4417A功率计连接了mount时，我正试图为432A做零罚款。
大多数敏感范围模拟指针“泵”接近零值，但当我从RF输入指针移除安装时完全稳定。
也许E4417A的射频输出“泄漏”了安装座上的一点点能量？
使用另一台E4417A和E4418A功率计也会发生同样的情况。

以上来自于谷歌翻译


     以下为原文

  Thanks. Problem was on bad connections. Yes, of course i have to use this mechanical front panel switch on the DVM, which activates front or read input's.

Is it better, while i'm zeroing the thermistor mount, that mount is not connected for the DUT's RF-output even RF power is off from it? I saw strange behaving, when mount was connected for the E4417A power meter and i'm trying to do Fine zero for 432A. Most sensitive range analog pointer "pumps" on near zero value, but when i remove mount away from the RF-input pointer is totally stable. Maybe E4417A's RF-output "leaks" little bit energy on the mount? Same behaving happening with another E4417A and E4418A power meter.
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张晓宁

2019-7-12 08:32:05
引用: ningee 发表于 2019-7-12 08:16
谢谢。
问题在于连接不良。
是的，当然我必须在DVM上使用这个机械前面板开关，它可以激活前置或读取输入。更好的是，当我将热敏电阻安装归零时，该安装座未连接到DUT的RF输出甚至RF

我想评论bar28关于432A仪表运动波动的旧帖子。
我也在E和N系列功率计上通过IEEE总线运行自动校准时看到了这一点。
由于STD安装座连接到UUT功率参考输出，我会在最敏感的范围内看到主要的432A仪表运动波动，同时尝试精细零点。
我能够验证笔记本电脑/控制器电池充电器的干扰导致了问题。
只有在STD安装座连接到UUT时才能观察到。
拔下充电器后，432A仪表的运动立即落在最敏感的范围内。
我有多个充电器，但并非所有充电器都会导致这个问题所以我不确定充电器是否有故障或者只是更嘈杂但我能够通过仅使用电池运行笔记本电脑来可靠地重复并消除这个问题。

以上来自于谷歌翻译


     以下为原文

  I want to comment on the very old post by bar28 regarding the 432A meter movement fluctuations. I've also seen this while running automated calibrations over the IEEE bus on E and N series power meters. With the STD mount connected to the UUT power reference output, i would see major 432A meter movement fluctuations on the most sensitive range while attempting a fine zero. I was able to verify interference from the laptop/controller battery charger was causing the problem. Only observable when the STD mount is connected to the UUT. Upon unplugging the charger the 432A meter movement instantly settled on the most sensitive range. I have multiple chargers and not all of them cause this problem so I'm not sure if the chargers are faulty or just more noisy but i was able to reliably repeat and eliminate this issue by running the laptop on batteries only.
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袁沁茹

2019-7-12 08:49:01
嘿 - 此刻碰到一个旧线程作为它的相关性。
我有E4418B服务手册，正在进行附录C第12页的计算。在表格底部，它们给出了扩展的2.859 Ui / uW的不确定性。
然后在表格下方的第一行，他们显示他们的最终不确定性值为3.030 uW。
我的问题是，Ui / uW单位是什么，他们是如何获得3.030美元的？
它与灵敏度系数有关，但我错过了最后一步。
我已经阅读了几节，我假设我忽略了一些简单的事情。
我有点模糊，仍在学习不确定性计算的细节，但我希望有人可以弥合Ui / uW数与最终不确定性之间的最后一个差距。

以上来自于谷歌翻译


     以下为原文

  Hey -  bumping an old thread here as its relavent to me at the moment.

I have the E4418B service manual and was going through the calculations in Appendix C, page 12.  At the bottom of the table, they give their expanded uncertainty of 2.859 Ui/uW.  Then in the first line below the table, they show their final uncertainty value of 3.030 uW.  My question is, what is that Ui/uW unit and how did they get to 3.030 uW?  It has something to do with the sensitivity coefficients, but I’m missing that last step.  I’ve read through the section a couple times and I’m assuming I’m overlooking something simple.

I'm a little fuzzy and still learning the finer points of uncertainty calculations, but I'm hoping someone can bridge that last gap between the Ui/uW number and the final uncertainty in uW.
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