The 1417 Four-Terminal Capacitance
Standard
consists of a 1 µF standard capacitor and two
precise inductive voltage dividers used to
scale the value of the 1 µF capacitor up to 1
F in decade steps. This arrangement provides
accuracy and stability unattainable with very
high-value true capacitors.
In addition to the seven direct-reading capacitance
values, an
infinite number of intermediate or higher capacitance values
can
be obtained by using external capacitors. An external capacitor
is
simply connected to the 1417's external standard terminals, either
directly or in parallel with a 1 µF internal standard, and
the resulting
capacitance is scaled in value by the 1417's inductive voltage
dividers.
The direct-reading accuracy of the 1417 is ±0.25% plus
ratio accuracy at test frequencies of 100, 120, or 1000 Hz. Since
the 1417 scaling ratios are precise and repeatable, better accuracy
can be obtained by measuring the actual value of the internal
1 µF standard or of an external standard before scaling.
The 1417 also servers as a standard of dissipation factor (D).
The
dissipation factor of the 1417 is intentionally set to 0.01 at
test
frequencies of 100, 120 and 1000 Hz. Basic D accuracy at these
frequencies is ±0.001.
The 1417 may also be used as a two-terminal capacitance
standard
when higher D values can be tolerated. In a two-terminal configuration,
D is less than 1 for capacitance values up to 1000 µF at
frequencies below 150 Hz. This feature allows the 1417 to be used
in calibrating the higher capacitance ranges of popular universal
or
RLC bridges.
One additional feature of importance is that all the 1417's
parameters are measurable (without disassembly) so, in effect,
its ultimate accuracy depends on the accuracy of the external
measurement equipment. |