| Electronics > Beginners |
| ESR Confusion |
| << < (5/7) > >> |
| BravoV:
--- Quote from: Terry01 on June 27, 2018, 10:06:10 am ---When would a large electrolytic be used @ 100kHz? What would happen if it was? I have a good machine that measures @ both 100 or 100k so which is correct? --- End quote --- Most low ESR cap datasheets stated that the capacitance was measured at the factory at 120 Hz, while the ESR (most datasheet called "Impedance") was measured at 100 Kilo Hertz. Some well known solid polymer also specified at 100 KHz "up to" 300 KHz, although not the common practice. So the correct frequency is measure them "according" to the manufacturer's specification, just check the datasheet. |
| Terry01:
--- Quote from: wraper on June 27, 2018, 10:31:34 am --- --- Quote from: Terry01 on June 27, 2018, 10:06:10 am ---If that graph is not for ESR did they just make it for a laugh or does BK not know nothing? --- End quote --- BK is fine, something wrong on your side. READ again, LCR measurement guidelines, not ESR. LOW ESR capacitor ESR usually is specified at 100kHz, be it small or big capacitor. General purpose capacitor ESR may be specified either at 120/100Hz or 100kHz. In both cases capacitance is usually specified at 120Hz or 100Hz. In practice there is no need to check ESR at 120Hz when checking components, unless you want compare apples vs apples with figure in a datasheet. Here you go, up to 18000uF with ESR specified at 100kHz. http://www.chemi-con.com/upload/files/5/1/74811667552d6c4d41a84c.pdf --- Quote ---When would a large electrolytic be used @ 100kHz? --- End quote --- Say SMPS. --- Quote ---If your LCR meter allows it, measure the impedance at the application frequency if you can. Seeing the impedance magnitude in ohms helps you use your intuition—and the phase angle tells you quickly if you have a pure reactance or a mixture of resistance and reactance. --- End quote --- --- End quote --- Nope! I am fine, no problems here. English is my 1st language so no help needed thanks. Just for fun I did a couple caps @ 100 Hz, 120 Hz, 1 kHz, 10 kHz and 100 kHz and just between just 120 Hz and 1 kHz the ESR measurement is half or more "less" at the higher frequency. Before you say meter is wrong or some other waffle I did a few. A big electrolytic may well/defo is! used in a SMPS, but it won't be working @ 100 kHz or the rest of the circuit wouldn't like it very much. Not at all in fact. Nice try but come on. Your getting deeper. That's all I won't reply no more. |
| wraper:
--- Quote from: Terry01 on June 27, 2018, 10:57:37 am ---Just for fun I did a couple caps @ 100 Hz, 120 Hz, 1 kHz, 10 kHz and 100 kHz and just between just 120 Hz and 1 kHz the ESR measurement is half or more "less" at the higher frequency. Before you say meter is wrong or some other waffle I did a few. --- End quote --- There is nothing wrong with measurements or your meter. Nobody said you'll get exactly the same figures. You just confirmed that measuring at 100kHz is completely valid to estimate condition of the capacitor. Read again: --- Quote from: wraper on June 27, 2018, 10:31:34 am ---In practice there is no need to check ESR at 120Hz when checking components, unless you want compare apples vs apples with figure in a datasheet. --- End quote --- The issue with measuring ESR at low frequencies it that you need a full blown LCR meter, as capacitance plays a big role in measurement. When measuring at 100kHz you can basically ignore the capacitance and assume that total impedance = ESR. |
| wraper:
--- Quote from: Terry01 on June 27, 2018, 10:57:37 am ---A big electrolytic may well/defo is! used in a SMPS, but it won't be working @ 100 kHz or the rest of the circuit wouldn't like it very much. Not at all in fact. Nice try but come on. Your getting deeper. --- End quote --- Big electrolytic capacitors are used in SMPS not for big capacitance which drops at high frequencies but for large ripple current they can handle. That's why they usually can be replaced with smaller value polymer capacitors which have much higher ripple current rating at the same capacitance. As you can see from the graphs, electrolytic caps are completely usable at 100 kHz. |
| Gyro:
--- Quote from: Terry01 on June 27, 2018, 10:57:37 am --- --- Quote from: wraper on June 27, 2018, 10:31:34 am --- --- Quote from: Terry01 on June 27, 2018, 10:06:10 am ---If that graph is not for ESR did they just make it for a laugh or does BK not know nothing? --- End quote --- BK is fine, something wrong on your side. READ again, LCR measurement guidelines, not ESR. LOW ESR capacitor ESR usually is specified at 100kHz, be it small or big capacitor. General purpose capacitor ESR may be specified either at 120/100Hz or 100kHz. In both cases capacitance is usually specified at 120Hz or 100Hz. In practice there is no need to check ESR at 120Hz when checking components, unless you want compare apples vs apples with figure in a datasheet. Here you go, up to 18000uF with ESR specified at 100kHz. http://www.chemi-con.com/upload/files/5/1/74811667552d6c4d41a84c.pdf --- Quote ---When would a large electrolytic be used @ 100kHz? --- End quote --- Say SMPS. --- Quote ---If your LCR meter allows it, measure the impedance at the application frequency if you can. Seeing the impedance magnitude in ohms helps you use your intuition—and the phase angle tells you quickly if you have a pure reactance or a mixture of resistance and reactance. --- End quote --- --- End quote --- Nope! I am fine, no problems here. English is my 1st language so no help needed thanks. Just for fun I did a couple caps @ 100 Hz, 120 Hz, 1 kHz, 10 kHz and 100 kHz and just between just 120 Hz and 1 kHz the ESR measurement is half or more "less" at the higher frequency. Before you say meter is wrong or some other waffle I did a few. A big electrolytic may well/defo is! used in a SMPS, but it won't be working @ 100 kHz or the rest of the circuit wouldn't like it very much. Not at all in fact. Nice try but come on. Your getting deeper. That's all I won't reply no more. --- End quote --- (@Terry01) Just for the avoidance of any confusion. The only way to confirm the health of a capacitor (or any other component come to that) is to measure it against the specification set out in its datasheet. If the datasheet specifies measurement at 100 or 120Hz then you should confirm the ESR at that frequency, however if the datasheet specifies a measurement 100kHz then the value needs to be measured at that frequency. Electrolytic capacitors are manufactured in many different families, some 'higher' ESR ones are intended for simple mains transformer/rectifier applications. Low ESR one are designed for high frequency SMPS uses, where the other ones would be ineffective and would quickly overheat. If you adhere to the datasheet figures specified for that specific part then there can be no confusion and no dispute. |
| Navigation |
| Message Index |
| Next page |
| Previous page |