IET Labs 1404 Series, Руководство по эксплуатации

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6
1404 Series
6 Maintenance
3.4 Temperature Cycling
The 1404 series can be used over a wide temperature
range however it is important to understand that
hysteresis (retrace) can cause errors of up to 20 ppm.
When a standard is subjected to relatively large tem-
perature changes, such as shipment, the calibrated
capacitance value may come back to a different
calibrated value at the same temperature after it has
been exposed to hot or cold conditions, this is called
hysteresis or retrace.
The 1404 Standard Capacitor utilizes invar plates and
spacers to minimize the eff ects of thermal expansion.
The standard should be keep in temperature condi-
tions close to 23°C ±1°C to minimize the error due
to hysteresis.
3.5 Design of the 1404
The 1404 is a three-terminal standard air capacitor.
The invar plates that make up the capacitor are her-
metically sealed in a can, fi lled with dry nitrogen to
minimize eff ects of both humidity and barometric
pressure.
The 1404 capacitors show very small changes with
orientation however this can be minimized by keeping
the 1404 in the upright orientation which is how it is
calibrated at IET Labs.
Additional information on the design of the 1404 can
be found at;
https://www.ietlabs.com/pdf/GR_
Experimenters/1963/GenRad_Experimenter_
Aug_1963.pdf
3.6 Environmental Conditions
3.6.1 Operating Temperature
For optimal accuracy, 1404 models should be used
in an environment of 23°C ±1°C. They should be
allowed to stabilize at those temperatures after any
signifi cant temperature variation.
3.6.2 Storage Temperature
The 1404 units should be maintained within the stor-
age temperature range of 0°C to 40°C to retain its
accuracy within the specifi ed limits.
3.7 Shipping and Handling
The 1404 Series should not be exposed to any excessive
shock or temperature extremes.