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AST (Accelerated Stress Testing) Definitions

Accelerometer for Table Control – An accelerometer that controls and measures the table surface.
Accelerometer for Product Control –  An accelerometer that controls and measures each product, as opposed to the entire table.
Accumulated Fatigue Damage Analysis - Accumulation of fatigue caused by vibration, based on Minor’s rule.
Access Port(s) – Port(s) that allow users to route cables and other equipment to and from the DUT.
Combined Environment (RS or ED) - Temperature and vibration
Device Under Test (DUT) – This is the product under test.  Also referred to as Unit Under Test (UUT).
Door Interlock – A safety device that can be configured to lock the chamber while LN2 is being used.
Fixture - A device that allows the user to mount a DUT to the shaker.
Gaseous Nitrogen (GN2) - An injection system designed for injection of dry GN2 gas into the chamber to minimize the moisture level.
Grms (G Root Mean Square) – A measurement used to compare and specify the energy in repetitive shock vibration systems.
HALT (Highly Accelerated Life Test) - This method uses step-by-step cycling of environmental variables such as temperature, shock, and vibration in order to force product failures.
HASS (Highly Accelerated Stress Screen) - Similar to the stresses used in HALT, HASS is an on-going screening test performed on regular production units.
Impactor – Device placed under the table that strikes the top of the table at a set frequency.
Impactor System Monitor – A device that monitors and indicates wear-and-tear of the impactors.
Liquid Nitrogen (LN2) – The gas used for extreme cold in AST systems.
Oxygen Monitor - Mounted on the outside of the chamber to ensure the level of oxygen in the room is at a safe level.
Mechanical Refrigeration – Removing heat using a refrigerant though the use of a mechanical compressor.
Multi-Zone Vibration Control – Control and balance uniformity for one, two, or four different zones on one table.
Peak Probability Distribution Function (PPDF) - Shows the graph of the probability distribution of the peaks and valleys of an accelerometer signal. This can be used to show the random nature of the table vibration.
Picket Fencing – Dramatic differences in displacement during a vibration test.
Power Spectral Density (PSD) – The distribution of a power signal over a specified frequency range.
Repetitive Shock (RS) Vibration - Resonating vibration from a repeated shock impulse.
Six Degrees of Freedom – The freedom of movement of an object on the XYZ-axes in an enclosed space.
Soft Start – Accurate control of very low Grms levels without DUT experiencing spikes. Incorporated in high frequency mode, low frequency mode, and synchronized shock mode.
Standoff – A metal piece that allows the fixture to be mounted to the shaker table
Step Stress – When a DUT receives increasing levels of stress until a failure occurs.
Synchronized Shock Test – Accelerates the rate of fatigue accumulation and allows DUT to experience as much as 1,500 Gpks. 
Thermocouple for Air Control – Air temperature is measured from the chamber’s air stream to the chamber controller.
Thermocouple for Product Temperature Control – Product temperature is controlled from the DUT to the chamber controller.
Transmissibility - Non-dimensional ratio of response acceleration to input acceleration in the time and frequency domains (compares response of two accelerometers).