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Low Level Measurements Hand Book

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Hari K

Low Level Measurements Hand Book

Post by Hari K » November 2nd, 2010, 9:04 am

The Low Level Measurements Hand Book 6th edition is a great resource that illustrates various techniques to perform Low Voltage measurements like

 Offset Voltages
 Noise
 Common-Mode Current and Reversal Errors

Here is the link to download the Low Level Measurements Hand Book 6th edition http://www.keithley.com/promo/wb/259

carlvanwormer
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Joined: March 6th, 2014, 3:16 pm
Country: United States

Re: Low Level Measurements Hand Book

Post by carlvanwormer » March 7th, 2014, 6:39 am

I just obtained the new (7th edition, at http://www.keithley.com/promo/wb/1401). I am confused by a few items which may be errors. For instance, FIGURE 1-24: Typical Digital Electrometer (page 1-29) has the output of the amplifier going to ground when the switch is set to Volts, Ohms. This is the same - as FIGURE 1-24: Typical Digital Electrometer in the 6th edition. If this really is wrong, is there some way for me to contact the editors of this document? I've found several other inconsistencies, but I want to make sure I'm just not being confused by unfamiliar conventions used in this document.

Norbert W
Keithley Applications
Keithley Applications
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Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: Low Level Measurements Hand Book

Post by Norbert W » March 10th, 2014, 3:34 am

Thanks for showing such interest in the Low Level Measurements Handbook.
Figure 1-24 gets complicated by incorporating a multitude of functions. For Volts (and Ohms) the riddle is solved
by taking guard ('guard output') as the internal reference level, e.g. the amplifier output voltage would be referred
to this potential.
If you have a list of suggestions for improvement I could certainly forward them internally, just send an eMail to
[email protected]
and I will take care.

carlvanwormer
Posts: 5
Joined: March 6th, 2014, 3:16 pm
Country: United States

Re: Low Level Measurements Hand Book

Post by carlvanwormer » March 10th, 2014, 6:49 am

If that is the case, then the drawing has been overly simplified. With switches in the Ohms position, the output of the amplifier is shown connected to ground, with the ranging amplifier connected to this same point, feeding ground to the analog output and the A/D converter. If there is other switching going on that would make sense of this confusion, a set of 4 figures, one fore each function, might be a much better communication tool. I will forward my other suggestions to the email address.
Thanks,
Carl

p.s. The quote, attributed to Einstein, “Everything should be made as simple as possible, but no simpler.” applies here.

Mary Anne T
Keithley Applications
Keithley Applications
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Contact:

Re: Low Level Measurements Hand Book

Post by Mary Anne T » April 4th, 2014, 7:58 am

You are correct that there are some inconsistencies with Figure 1-24 of the 7th edition of the Low Level Handbook. I have corrected this schematic and have attached the latest version. Thank you for calling this to our attention.
Attachments
Fig 1-24 LLHB Apr 4 2014.docx
(105.76 KiB) Downloaded 1351 times

carlvanwormer
Posts: 5
Joined: March 6th, 2014, 3:16 pm
Country: United States

Re: Low Level Measurements Hand Book

Post by carlvanwormer » April 4th, 2014, 8:18 am

It does look more complete, but I'm still getting confused. It looks like the output of the amplifier (Ax-1) is grounded for Volts and Ohms. since this is also the prescaler for the A/D converter, the signal is always grounded, unless the B ground symbol is not really ground. A note on the S and B ground signals might help reduce the confusion.

Also, the graphics for the amplifier has the + input entering the middle of the amplifier.

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