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03/26/2005 Entry: "HP 5061A C Field Settings"

I've run a series of tests on the 5061A to try to nail down the C field behaviour. I plotted the offset versus GPS, with one hour averaging, for 72 hours at three different settings. In each case, I waited at least 48 hours to let the unit stablize after making the change. Here are the results:

4.50 -7.8x10-13
5.00 +1.3x10-12
5.50 +3.3x10-12

That comes out to just about 8x10-14 per minor division, just as the HP book says (I wasn't sure if the sensitivity would be the same with the FTS tube as with the HP version).

Based on this, I should set the C field to 4.60, which I'm doing now.