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Standard capacitors

Highly stable standards

We have developed highly stable four terminal-pair capacitance standards of compact design. Their stability derives from using a ceramic dielectric and by keeping the standards at constant temperature using a two-stage oven.

Two BNC connectors are attached to the built-in platinum resistance thermometer (PRT) to monitor the internal temperature of the capacitor. Accurate capacitance measurement can be made via four terminal-pair coaxial BPO (MUSA) connectors. Each capacitor is housed in a metal box and requires only a simple 12 Volt DC supply to operate the temperature controller. A feature of this capacitor is that the value does increase by about 90 parts per million (ppm) with each factor of ten increase in the measurement frequency.


  • Selected capacitance values in the range 50 pF to 1 μF are available
  • High stability
  • Capacitance value close to nominal
  • Small dissipation factor
  • Frequency dependence is ~90 ppm for each factor of 10 increase in measurement frequency
  • Compact design with standard four terminal-pair BPO (MUSA) connectors
  • Built-in two-stage oven controller with an independent 100 Ω PRT sensor as standard
  • 1 year warranty
  • Calibration certificate available



Selected values between 50 pF to 1 μF available
  Within a tolerance of ± 100 to ± 500 ppm depending on value, at 1 kHz
Dissipation factor Around 0·00005 to 0·0005 depending on value at 1 kHz
Frequency dependence ~ 90ppm for each factor of 10 increase in measurement frequency
Drift ± 0·05 ppm/day typically
Stability (Short term) ± 0·01 ppm/hour
Max Working voltage 30 V rms
Warm-up time 1 hour  (allow 48 hours to stabilise before use)
Operating ambient temperature 15 °C to 24 °C
Relative humidity 20% to 60% non-condensing
Storage temperature range 5 °C to 70 °C
Power requirements 12 V DC ± 0·5 V
Power consumption 15 watts max. during initial warm-up, 2 watts after 1 hour, dependent on ambient temperature
Packaging 93mm high, 123mm wide, 125mm depth, plus 50 mm height of BPOs
Weight 1.4 kg
Warranty 1 year return to base

The best measurement capability, expressed as an expanded uncertainty (k = 2) is 70 ppm of nominal value, which applies to a wide range of instruments and test conditions.

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