- Values 0.001 µF (1 nF) to 1000 µF
- Stability as good as ±0.01 %/year
- Two-to-five terminal configuration, depending on model
- Calibration accredited to ISO-17025 included
- 3 year warranty included
GenRad 1409 Series Standard Capacitor1409 GenRad
GenRad 1409 Standard Capacitors
The GenRad 1409 is a series of highly stable, cost-effective capacitance standards. With a low temperature coefficient and low losses, they cover a wide range of values, from 1 nF to 1,000 µF.
Key features
- Excellent stability, better than 100 ppm per year
- Accurate, repeatable measurements of high capacitance values
- Calibrated in both 2- and 3-terminal configurations, at 100 Hz or 1 kHz depending on the capacitance value
- Sales and applications support from IET Labs (sales@ietlabs.com)
Design
- 1 nF to 1 µF: silvered-mica and foil construction, for use as a two- or three-terminal laboratory standard.
- 1 µF to 10 µF: hermetically sealed polystyrene.
- Above 10 µF: hermetically sealed metallized polypropylene sulfide (MPPS).
Manufacturing
- Same methods as in 1957: IET Labs builds the 1409 with the same fixtures and techniques GenRad used when the series was developed in 1957. Each unit is handmade in the USA.
- Selected mica: the best available silvered-mica sheets are stacked alternately to reach the required capacitance. Every sheet is tested individually, so that its dissipation factor is low enough for the finished capacitor to meet specification.
- Clamping: the finished stack is placed in a clamping structure that compresses the mica and keeps it mechanically stable.
- Artificial aging: each element is aged by temperature cycling to improve stability, and then mounted in its housing.
- Adjustment: a final capacitance adjustment brings the unit into specification.
- Humidity protection: a thick desiccant sheet covers the whole assembly, followed by a coat of potting material that minimizes the effect of humidity on capacitance and dissipation factor. Together with the aging, this keeps the 1409 stable for decades.
Long-term behavior
Typical capacitors observed over decades show random fluctuations of less than 0.01% in measured capacitance, with no evidence of systematic drift. The elements are selected for low dissipation factor and stabilized by heat cycling. They are housed in cast aluminum cases with silica gel for continuous desiccation, and the cases are sealed with high-temperature potting material.
Connections
Three gold-plated, low-thermal-emf binding posts are on the top of the case. Removable banana plugs on the bottom allow convenient parallel connection without error.
Trzy rzeczy do sprawdzenia w oryginale przed publikacją:
- MPPS: zapis “metallized polypropylene sulfide” wygląda na błąd. Typ MPPS zwykle oznacza metallized polyphenylene sulfide (polisiarczek fenylenu), więc warto zajrzeć do karty katalogowej producenta. W tekście zostawiłem brzmienie z oryginału.
- Nakładające się zakresy: w oryginale 1 µF jest wymieniony zarówno w zakresie miki (do 1 µF), jak i polistyrenu (od 1 µF). Prawdopodobnie granica jest po prostu nieostra, ale dokładna wartość graniczna wymaga sprawdzenia.
- Znak “+ 0.01%”: w oryginale jest sam plus, a kontekst sugeruje ±0,01%. Przepisałem to jako “less than 0.01%”, co jest zgodne ze sensem.
