Agilent Technologies E5100A, Programming Manual, Page: 363 / 373

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Measuring Load Resonance Frequency (FL) Using
a CL Board with Fixed C
Introduction
When a load capacitance (CL) is connected in series or in parallel to a crystal resonator , the
lower of the two frequencies with zero phase will be generally higher than that when no
load capacitance is connected. This lower frequency is called load resonance frequency (FL)
and varies depending on the CL value . When a crystal resonator is employed in a physical
electronic circuit, CL will always be connected to the resonator . Therefore , FL is a critical
parameter .
When the crystal resonator FL needs to be evaluated for trading, each of the parties involved
in the trade must measure the FL by connecting the same CL to the resonator . F or example , it
has been common to measure the CL with an LCR meter while adjusting it with the trimmer .
However , conventional measurement procedures resulted in varying FL values depending
on the accuracy of the LCR meter and the manner in which the FL is measured. Another
drawback to conventional methods is that the CL set with the trimmer could vary due , for
example , to vibrations , thus producing dierent evaluations in relation to the same resonator
among traders .
The measurement procedure presented here uses a specially designed command to determine
the FL by connecting a CL board having a precisely measured xed C and calculate the FL for
the desired (or target) CL through corrections . This procedure can minimize errors caused, for
example , by improper trimmer adjustments and stray capacitance .
The 41900A network text xture and the 41901A SMD network text xture come with
a CL board with a xed load capacitance . Each of these CL values is precisely measured for
utmost accuracy in determining the FL for the desired CL value .
Measuring Load Resonance Frequency (FL) Using a CL Board with Fixed C K -1