Extending the Calibration Capabilities of High Resistance

We present new possibilities for the calibration of resistors in the range from
$1\ \mathrm{M}\Omega$
to
$1\ \mathrm{G}\Omega$
. Presently, this range is covered by a potentiometric bridge and is based on a
$1\ \mathrm{M}\Omega$
standard resistor, calibrated with a cryogenic current comparator (CCC). The step-up to
$1\ \mathrm{G}\Omega$
takes place using the 10:1 capability of the potentiometric bridge. We have now extended the usable range of the CCC to
$10\ \mathrm{M}\Omega$
and established a calibration capability in this range using the ultrastable low-noise current amplifier (ULCA).