Laboratory reference capacitor.
The 1404 Reference Capacitor. Standard Capacitance.
These capacitors have been designed as primary reference standards of capacitance with which working
standards can be compared.
The 1404 Series are the standard of choice in metrology labs, and still used today by standards bodies
around the world.
1409 Reference Capacitor
|1404||1404 Reference Capacitor. Standard Capacitance
Available in 10, 100, and 1000pF
20 ppm per year stability
Hermetically sealed in dry nitrogen
1404-9701 1404-A, 1000pF
1404-9703 1404-C, 10pF
In combination with an accurately known external resistor, this capacitor also becomes a standard of
All critical parts of the plate assembly are made of invar for stability and low temperature coefficient.
After heat cycling and adjustment the assembly is mounted in a heavy brass container, which,
after evacuation, is filled with dry nitrogen under pressure slightly above atmospheric and sealed.
The container is mounted on an aluminum panel and protected by an outer aluminum case.
Each capacitor is subjected to a series of temperature cycles to determine hysteresis and
temperature coefficients and to stabilize the capacitance.
Two locking G874 coaxial connectors are used as terminals.
The outer shell of one is connected to the case, but the outer shell of the other is left unconnected
to permit the capacitor to be used with an external resistor as a dissipation -factor standard.
Calibration: A certificate of calibration is supplied with each capacitor, giving the measured direct
capacitance at l kHz and at 23°±°C.
The measured value is obtained by a comparison to a precision better than ± 1ppm with working standards
whose absolute values are known to an accuracy of ±5ppm, determined and maintained in terms of reference
standards periodically measured by the National Institute of Standards and Technology.
Adjustment Accuracy: The capacitance is adjusted before calibration with an accuracy of ±5ppm to a capacitance about 5ppm above the nominal value relative to the capacitance unit maintained by the reference standards.
Stability: Long term drift is less than 20 ppm per year. Maximum change with orientation is 10ppm and is
Temperature Coefficient of Capacitance: 2 ±2ppm/ °C for 1404-A and -B, 5 ±2ppm/ °C for 1404-C,
from -20°C to +65°C. A measured value with and accuracy of ±1ppm/ °C is given on the certificate.