21982 Views 6 Replies Latest reply: Apr 30, 2014 12:48 PM by dkemppai
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# Volts per second versus volt seconds

I've heard the term volts per second and also volt seconds.  First, neither of these make sense, what could they mean?  And second, are they the same or are they something different?

• 1 posts since
Apr 14, 2014
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Apr 16, 2014 5:56 PM (in response to Riley)
Volts per second versus volt seconds

Volts per second is also called slew rate.  This is used to measure how fast the output of an op-amp can change (dV/dt).  It is usually expressed in Volts/us.

Volt seconds is a term used to express glitch energy, such as the glitch when a DAC changes values.  It's just the voltage peak (low extreme to high extreme) multiplied by the length of the glitch in time.  Glitch energy is usally spec'ed at the worst cases which would normally be at the major carry points (ie. 01111 to 10000).

• 1 posts since
Dec 26, 2012
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Apr 30, 2014 12:06 PM (in response to Riley)
Volts per second versus volt seconds

Volt seconds is also used in sizing inductors.  As is how many volts over how many (micro)seconds can it take before it saturates.

• 1 posts since
Apr 30, 2014
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Apr 30, 2014 12:48 PM (in response to SherpaDoug)
Volts per second versus volt seconds

Volts per second is how fast the voltage is changing. It's the same as the derivative dv/dt, and same as slew rate (usually, slew rate is volts / microsecond or similar value). How many volts do you change in how many seconds.

Volt-Seconds is often used in transformer design. With transformers, even though you are moving power from the primary to the secondary, you need to ensure that your core doesn't saturate. In this case the volts is relativley constant (usually not changing much), as opposed to above. Volt-Seconds, is volts applied times the number of seconds it was applied for (Thus Volt * Seconds or Volt-Seconds). In a transformer, you need to 'reset' the core, or apply a negative "Volt-Seconds" value so that the average of Volt-Seconds is zero.

Very different values, with similar names.

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