Because measuring an electrolytic capacitor with an analog or digital capacitance meter can MISLEAD a technician into believing that a defective capacitor is good. This can waste your precious time and you are unable to repair the equipment. Which means you can’t charge your customer! If you don’t test for ESR on the capacitor, you will always miss the bad capacitor. Normally, these bad capacitors have high ESR reading which your normal multimeter or digital capacitance meter can’t measure. Only by using the ESR meter, you will be able to measure the ESR on the capacitor and you will not be fooled by capacitors with bad ESR. ESR meter can even work IN-CIRCUIT, which means you don’t have to solder out the capacitor in order to measure it using normal capacitor tester, which would not be accurate anyway.
Do you know that ESR meters can perform other wonders besides checking the ESR of a capacitor? Some digital ESR meter have the features of checking:
- Low ohms resistor such as 0.22 ohm, 0.33 ohm and etc.
- Horizontal yoke coil winding of a picture tube, inductor and primary winding of a transformer – If a shorted turn is present, the inductance drops dramatically and the meter will show the ohms reading.
- Horizontal output transistor (HOT) in a monitor or TV – If an open-circuit reading is obtained, the short-circuit is elsewhere. If the short-circuit remains, the transistor is faulty.
- Short-circuit in the track, usually trace to the components – You can use the ESR meter to locate short-circuits on printed circuit boards by measuring the actual track resistance. If the reading increases as you probe further along the track, you know you’re going in the wrong direction!
- Speakers, amplifier etc – The pulses have a fast rise/fall time, so it would probably make a crude RF signal injector as well.
- The condition of both the normal and rechargeable batteries – Flat and faulty battery will have high ESR.