Test Data and Special Test Requirements

Typically, precision oscillators are individually tested by the manufacturer
for frequency drift over time and temperature, output level and spurious
signals, phase noise (when specified), tuning range, and warm-up
characteristics. Additional tests may be performed for a wide range of
requirements including:

Shock and Vibration
Testing

Units are often tested to ensure survival in brutal environments and to
determine the performance degradation in the presence of vibration. Specified
vibration is usually random, expressed as a power spectral density but sine
vibration is occasionally invoked. Wenzel Associates has the in-house capability
to measure vibration induced phase-noise.

Altitude and
Space Testing

Oscillators may be tested in a vacuum chamber to determine the detrimental
effect of low pressure and the corresponding drop in thermal conductivity.
Wenzel Associates has the in-house capability to test small oscillators over
temperature down to about 10 microtorr.

Thermal Shock

Oscillators are often exposed to several extreme temperature swings without
power applied to uncover mechanical flaws. Oven oscillators, especially flask
insulated designs, are somewhat immune to thermal shock since the ovens usually
have significant thermal mass well insulated from the ambient. Consequently,
much of the oscillator circuitry may not see the rapid temperature change or
even the temperature extremes if the test is performed too quickly. Thermal
shock tests can also incorporate a start-up test to ensure that the oscillator
will start at the temperature extremes.

Radiation
Hardness

Oscillators traveling into space may encounter significant levels of
radiation. Usually radiation testing is difficult to accomplish and, as an
alternative, the oscillators are designed using guidelines. Swept-quartz
crystals are required and the design is analyzed for the detrimental effects of
significant transistor beta decreases and high leakage currents. Many component
types are avoided and current limiting resistors are added to prevent damaging
radiation induced currents.

Radiated and
Conducted Emissions

Radiated emissions may be tested by specially equipped labs but these tests
are frequently performed on complete instruments instead of individual
components. Conducted emissions are easily performed with a spectrum analyzer
and a few additional components. Since most precision oscillators are sealed in
metal enclosures, the conducted emissions test is sufficient to determine the
level of RF leakage.

Minimal susceptibility to acoustical noise, magnetic fields, humidity, or
even ambient light may appear as a special requirement.

Test data for each oscillator may range from a simple attributes sheet to a
completed test procedure with supporting documents and component tracking. The
level of documentation depends on the customer's particular program.

View the Oscillator
Catalog