Hello all
Merry Christmas to you all even though it will probably be wel over if you get around to reading this.
Just got myself an ESR meter and have spent a few hours going through the caps on a TV power board that I know has issues.
Seeing how it works.
I am not using the small ESR table that is attached to the device to interpret the output.
Instead I am using the cap manufacturer's datasheets for the appropriate cap series which are pobably more reliable.
In this case the manufacturer is CapXOn and their datasheets give impedance values in Ohms.
One example: CapXOn GF Series.
470 uF 16 V capacitor has Max Impedance at 20C / 100 KHz = 0.095 ohms
My ESR meter reading for this cap in situ on the board is 0.22 ohms.
Which is way over the max figure of 0.095 ohms on the datasheet.
Now here's the thing. When I look at the "Typical ESR values" table on the meter the "typical" value
for that cap is 0.21 ohms which is pretty much spot on. In other words it's fine leave it alone.
So I ask myself : Why the difference between the "typical" values and the datasheet max values?
Does anyone have any idea how these "typical" ESR values that you find scattered about are caculated?
They also vary from chart to chart I have noticed.
I know that there is an cap impedance ratio that is temperature dependent, and the rated temperature of
a typical cap is 105C, and I am wondering if that has any part to play in determining these typical values.
Is there a formula or some kind of approximation rule based on capacitance, voltage, impedance ratio etc?
How far away should an ESR reading be from the typical reading to be considered a failure? 10%? 20%?
Any thoughts?
Cheers
Ray Pooley
Merry Christmas to you all even though it will probably be wel over if you get around to reading this.
Just got myself an ESR meter and have spent a few hours going through the caps on a TV power board that I know has issues.
Seeing how it works.
I am not using the small ESR table that is attached to the device to interpret the output.
Instead I am using the cap manufacturer's datasheets for the appropriate cap series which are pobably more reliable.
In this case the manufacturer is CapXOn and their datasheets give impedance values in Ohms.
One example: CapXOn GF Series.
470 uF 16 V capacitor has Max Impedance at 20C / 100 KHz = 0.095 ohms
My ESR meter reading for this cap in situ on the board is 0.22 ohms.
Which is way over the max figure of 0.095 ohms on the datasheet.
Now here's the thing. When I look at the "Typical ESR values" table on the meter the "typical" value
for that cap is 0.21 ohms which is pretty much spot on. In other words it's fine leave it alone.
So I ask myself : Why the difference between the "typical" values and the datasheet max values?
Does anyone have any idea how these "typical" ESR values that you find scattered about are caculated?
They also vary from chart to chart I have noticed.
I know that there is an cap impedance ratio that is temperature dependent, and the rated temperature of
a typical cap is 105C, and I am wondering if that has any part to play in determining these typical values.
Is there a formula or some kind of approximation rule based on capacitance, voltage, impedance ratio etc?
How far away should an ESR reading be from the typical reading to be considered a failure? 10%? 20%?
Any thoughts?
Cheers
Ray Pooley
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