Robert Liang

<p>Hello,</p> <p>I have a Keithley 6430 (as a small current source) and a 6517B (as a picoammeter), and I want to connect one from another to do some tests.&#160;However, the triaxial connector conductor definition of these two instruments are different;(So I cannot connect them directly using a triaxial&#160;cable).</p> <p>These definition are as follows (inner conductor, inner shield, outer shield):<br> * Keithley 6430: (HI, GUARD, LO)<br> * Keithley 6517B: (HI, LO, GUARD)</p> <p>The previous method I tried is using 2 [triaxial-to-alligator-clip] cable, however the noise introduced by this connection seems to be large(about 1pA/sqrt[Hz] @ 0.1Hz) even with a shielding case.</p> <p>To solve the above problems, I'm ordering a customized low-noise triaxial cable (6430 and 6517 HI-to-HI, LO-to-LO). There're two soldering plans, and&#160;I can't decide:</p> <p>* 1st plan: 6430 connector direct connect to cable; 6517 connector's&#160;outer shield (Guard)&#160;disconnected, inner shield (LO) is soldered to cable's outer shield layer. (In this case, 6430's 'Guard'&#160;tightly surround 'HI', 6517's connector requires soldering).</p> <p>* 2nd plan: 6517B connector direct connect to cable; 6430 connector's inner shield (Guard) disconnected, outter shield (LO) is soldered to cable's inner shield layer. (In this case, 'LO' tightly surround 'HI', 6430 side connector requires soldering).</p> <hr> <p>&#160;My questions are as follows:</p> <p>&#160;1. Which plan is better?</p> <p>2. Can any of these plans work? (Are they worth to try? Any suggestions of selecting cable?)</p> <p>3. If they can't work, is there a better solution?</p> <p>Thank you!</p>

Thanks for your answer!

It seems that the auto-zero once remote command will abort the trigger model. Actually my trigger model is like this: Wait for ext trigger -> Acquisition 500s -> Wait for ext trigger -> Acquisition 500s -> ... So except for the beginning, no other time that I could insert the AZERO once command. Although I'm still in the designing step, I'm afraid that it will drift during the whole measurement progress.

At least I think the support of auto-zero once in trigger model is necessary, but as I known it doesn't.

So please tell me if this instrument will update its autozero value if I switch the AZERO configuration from OFF to ON then to OFF by moving the configuration list in trigger model? Will it work? 

Thanks again.

Hi, experts.

I have searched a lot, but no result.

I want to achieve periodically auto-zeroing using the trigger model every two seconds. That is because I have tested that the 'auto-zero on' configuration clearly lower the data output rate. To achieve the balance of offset and data rate, I have to reduce the frequency of auto-zero but not close it.

I found there's no block in the 'trigger model' is about the auto-zero configurations, but some blocks for moving the 'configuration lists'. So currently I set two configuration lists, one with AZERO on, another off. For every two seconds, I change configuration from OFF to ON and then to OFF immediately to emulate 'AZERO once' function. This ON-OFF-ON switching will take 0.7 seconds as I tested.

My questions are:
1. I'm not sure that this method can work, and is there easier or more elegant way to achieve that?
2. My DC measurement for one time will last for at least 500 seconds. If I have to choose AZERO ON or AZERO OFF, which is better on precision?

Thank you very much.