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SEMI, the industry association for the semiconductor industry, has developed the SEMI F47 voltage sag immunity standard. Information about SEMI F47 – The Voltage Sag Immunity Standard. What does SEMI F47 do? SEMI F47 sets out the required voltage sag tolerance for semiconductor fab equipment The latest edition is SEMI F47-0706 (Reapproved 0812). PSL led …

How 4-Terminal Resistors Work

In a 4-terminal resistor, an ultra-precise resistor (green) is connected to 4 terminals through small, but unknown, resistors (red). These unknown resistors are the combination of lead resistance, screw terminal resistance, connection wire resistance, and other sources of errors. Typical values for these unknown resistors range from 0.01 ohms to 0.2 ohms, and the values …

Eleven Quick, Simple Fixes to Increase Sag Immunity

Here are eleven quick, simple fixes that will increase voltage sag immunity. Of course, like every engineering change, there are tradeoffs that you will need to consider as you’re selecting a solution. 1. Find and fix the problem. Yes, it’s an obvious suggestion. But it’s the best place to start. Figure out exactly what is causing …

Sources of Voltage Sags

What are Voltage Sags? Voltage sags are brief reductions in the voltage on ac power systems. (The American “sag” and the British “dip” have exactly the same meaning, and may be used interchangeably.) How brief? Between 1/2 cycle and a few seconds. Disturbances that last less than 1/2 cycle are commonly called “low frequency transients”; …

Voltage Sag Sensitivity

Why does equipment fail when there are voltage sags on ac power systems? There is one obvious way, and four not-so-obvious ways. Here is some information about voltage sag sensitivity. Equipment fails because there isn’t enough voltage This is the obvious way — if there is not enough voltage on the ac power system to …

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