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How do I calculate the inductance and capacitance out from the barrier to make sure it is less than the sensor values? The output capacitance and inductance from your zener barrier is irrelevant ...
Answer
#3: Post edited
by
Andy aka
·
2020-07-10T10:30:08Z (almost 4 years ago)
- > _How do I calculate the inductance and capacitance out from the barrier to make sure it is less than the sensor values?_
The output capacitance and inductance from your zener barrier is unimportant - you design the barrier components (fuse, zeners and output resistor) to limit the short circuit current and limit the open circuit voltage. Then, you use graphs for the gas group your unit is to be installed in to see if there might be a spark energy that can be ignited should the sensor have too much inductance or capacitance that, under fault condition(s).- In other words, the barrier buffers (fuse, zeners and resistor) your switching converter to intrinsically safe output levels. But, it's only intrinsically safe if what you hang on the output (the sensor) is permitted i.e. less than the maximum allowable capacitance and inductance.
- > _I'm just wanting to understand the methodologies behind this question to better understand the concept to use in all of my engineering moving forward._
It seems you my be a little inexperienced in this area but it should all become clear when you look in the appropriate standards for intrinsically safety. Your zener barrier maximum output voltage dictates the maximum capacitance that your sensor (and its wiring) can have AND your zener barrier maximum short circuit current dictates the maximum inductance that your sensor (and its wiring) can have.
- > _How do I calculate the inductance and capacitance out from the barrier to make sure it is less than the sensor values?_
- The output capacitance and inductance from your zener barrier is irrelevant - you design the barrier components (fuse, zeners and output resistor) to limit the short circuit current and limit the open circuit voltage. Once designed, the barrier is a zener limited voltage source in series with an infallible resistor. It does not store energy and it does not have any capacitance or inductance.
- Then, using graphs for the gas group your unit is to be installed in, you see if there might be a spark energy that can ignite a gas should the sensor have too much inductance or capacitance (when connected to the barrier).
- In other words, the barrier buffers (fuse, zeners and resistor) your switching converter to intrinsically safe output levels. But, it's only intrinsically safe if what you hang on the output (the sensor) is permitted i.e. less than the maximum allowable capacitance and inductance.
- > _I'm just wanting to understand the methodologies behind this question to better understand the concept to use in all of my engineering moving forward._
- It seems you my be a little inexperienced in this area but it should all become clear when you look in the appropriate standards for intrinsically safety. Your zener barrier maximum output voltage dictates the maximum capacitance that your sensor (and its wiring) can have AND, your zener barrier maximum short circuit current dictates the maximum inductance that your sensor (and its wiring) can have.
#2: Post edited
by
Andy aka
·
2020-07-08T12:22:57Z (almost 4 years ago)
- > _How do I calculate the inductance and capacitance out from the barrier to make sure it is less than the sensor values?_
- The output capacitance and inductance from your zener barrier is unimportant - you design the barrier components (fuse, zeners and output resistor) to limit the short circuit current and limit the open circuit voltage. Then, you use graphs for the gas group your unit is to be installed in to see if there might be a spark energy that can be ignited should the sensor have too much inductance or capacitance that, under fault condition(s).
In other words, the barrier converts (fuse, zeners and resistor) convert your switching converter to intrinsically safe output levels. But, it's only intrinsically safe if what you hang on to the output is permitted i.e. less than the maximum allowable capacitance and inductance.- > _I'm just wanting to understand the methodologies behind this question to better understand the concept to use in all of my engineering moving forward._
It seems you my be a little inexperienced in this area but it should all become clear when you look in the appropriate standards for intrinsically safety.
- > _How do I calculate the inductance and capacitance out from the barrier to make sure it is less than the sensor values?_
- The output capacitance and inductance from your zener barrier is unimportant - you design the barrier components (fuse, zeners and output resistor) to limit the short circuit current and limit the open circuit voltage. Then, you use graphs for the gas group your unit is to be installed in to see if there might be a spark energy that can be ignited should the sensor have too much inductance or capacitance that, under fault condition(s).
- In other words, the barrier buffers (fuse, zeners and resistor) your switching converter to intrinsically safe output levels. But, it's only intrinsically safe if what you hang on the output (the sensor) is permitted i.e. less than the maximum allowable capacitance and inductance.
- > _I'm just wanting to understand the methodologies behind this question to better understand the concept to use in all of my engineering moving forward._
- It seems you my be a little inexperienced in this area but it should all become clear when you look in the appropriate standards for intrinsically safety. Your zener barrier maximum output voltage dictates the maximum capacitance that your sensor (and its wiring) can have AND your zener barrier maximum short circuit current dictates the maximum inductance that your sensor (and its wiring) can have.
#1: Initial revision
by
Andy aka
·
2020-07-08T10:05:30Z (almost 4 years ago)
> _How do I calculate the inductance and capacitance out from the barrier to make sure it is less than the sensor values?_ The output capacitance and inductance from your zener barrier is unimportant - you design the barrier components (fuse, zeners and output resistor) to limit the short circuit current and limit the open circuit voltage. Then, you use graphs for the gas group your unit is to be installed in to see if there might be a spark energy that can be ignited should the sensor have too much inductance or capacitance that, under fault condition(s). In other words, the barrier converts (fuse, zeners and resistor) convert your switching converter to intrinsically safe output levels. But, it's only intrinsically safe if what you hang on to the output is permitted i.e. less than the maximum allowable capacitance and inductance. > _I'm just wanting to understand the methodologies behind this question to better understand the concept to use in all of my engineering moving forward._ It seems you my be a little inexperienced in this area but it should all become clear when you look in the appropriate standards for intrinsically safety.