Capasitor ESR. Good or Bad?

To measure the capacitor in a correct and accurate way it needs to be discharged and removed from the circut.

Capacitors lose their parameters due to the passage of time, increased operating temperature, or leakage. Caps can be damaged by a short inside the part. Before measuring the capacitor capacity it’s a good idea to measure ist the resistance. Good cap resistance should be rising to infinity when it’s measured (OL). If there is a steady indication of the resistance capacitor is actually acting like a resistor, and it needs to be replaced. Very often tantalum capacitors don’t lose their capacity but they can be shorted out, so it is a good practice to measure their resistance. Electrolytic capacitors can have an increased ESR but proper capacity measurement, in my opinion, they need to be replaced.

What is ESR?

Practical capacitors and inductors as used in electric circuits are not ideal components with only capacitance or inductance. However, they can be treated, to a very good degree of approximation, as being ideal capacitors and inductors in series with a resistance; this resistance is defined as the equivalent series resistance (ESR). If not otherwise specified, the ESR is always an AC resistance, which means it is measured at specified frequencies, 100 kHz for switched-mode power supply components, 120 Hz for linear power-supply components, and at its self-resonant frequency for general-application components. Additionally, audio components may report a “Q factor”, incorporating ESR among other things, at 1000 Hz.

The ESR parameter characterizes the imperfections of the capacitor, their differences from the ideal capacitor. The ESR parameter is expressed in Ω as in the case of ordinary resistance. A lower ESR parameter means better for a capacitor. increased value of the capacitor ESR (resistance) results in an increase in operating temperature. It can cause the capacitor to bulge and the electrolyte to dry out. The ESR value of capacitors depends on their capacity and rated voltage. If the capacitance of the condenser is greater, the ESR is lower, the higher the rated voltage, the lower the ESR. The ESR parameter is not constant for all capacitors.

Below you will find a table, worst-case scenario for electrolytic caps. I’m using the custom meter for measuring the ESR of the capacitor. Tester Elko-ESR Atlas ESR70 is the best one in my opinion but you can buy a cheap LCR-T4, will do the work. 

MAXIMUM ALLOWABLE ESR (in Ohms) Standard Aluminum Electrolytic Capacitors. Based on SENCORE LC102 Capacitor-Inductor Analyzer

Capacity in µF

1.5V

3.0V

6.0V

10V

15V

20V

25V

35V

50V

100V

200V

300V

400V

500V

600V

1000V

1.0

663

663

663

663

454

464

464

464

332

332

265

265

265

265

265

265

1.5

442

442

442

442

310

310

310

221

221

177

177

177

177

177

177

177

2.2

302

302

302

302

211

211

211

151

151

121

121

121

121

121

121

121

3.3

201

201

201

201

141

141

141

101

101

80

80

80

80

80

80

80

4.7

141

141

141

141

99

99

99

71

71

56

56

56

56

56

56

56

6.8

98

98

98

98

68

68

68

49

49

39

39

39

39

39

39

39

10

66

66

66

66

46

46

46

33

33

27

27

27

27

27

27

27

15

44

44

44

44

31

31

31

22

22

18

18

18

18

18

18

18

22

30

30

30

30

21

21

21

15

15

12

12

12

12

12

12

12

33

20

20

20

20

14

14

14

10

10

8.04

8.04

8.04

8.04

8.04

8.04

8.04

47

14

14

14

14

9.88

9.88

9.88

7.06

7.06

5.65

5.65

5.65

5.65

5.65

5.65

5.65

68

9.76

9.76

9.76

9.76

6.83

6.83

6.83

4.88

4.88

3.90

3.90

3.90

3.90

3.90

3.90

3.90

100

6.63

6.63

6.63

6.63

4.64

4.64

4.64

3.32

3.32

2.65

2.65

2.65

2.65

2.65

2.65

2.65

150

4.42

4.42

4.42

4.42

3.10

3.10

3.10

2.21

2.21

1.77

1.77

1.77

1.77

1.77

1.77

1.77

220

3.02

3.02

3.02

3.02

2.11

2.11

2.11

1.51

1.51

1.21

1.21

1.21

1.21

1.21

1.21

1.21

330

2.01

2.01

2.01

2.01

1.41

1.41

1.41

1.01

1.01

.804

.804

.804

.804

.804

.804

.804

470

1.41

1.41

1.41

1.41

.988

.988

.988

.706

.706

.565

.565

.565

.565

.565

.565

.565

680

.976

.976

.976

.976

.683

.683

.683

.488

.488

.390

.390

.390

.390

.390

.390

.390

1000

.663

.663

.663

.663

.464

.464

.464

.332

.332

.265

.265

.265

.265

.265

.265

.265

1500

.442

.442

.442

.442

.310

.310

.310

.221

.221

.177

.177

.177

.177

.177

.177

.177

2200

.302

.302

.302

.302

.211

.211

.211

.151

.515

.121

.121

.121

.121

.121

.121

.121

3300

.201

.201

.201

.201

.141

.141

.141

.101

.101

0.80

0.80

0.80

0.80

0.80

0.80

0.80

4700

.141

.141

.141

.141

.099

.099

.099

.071

.071

.056

.056

.056

.056

.056

.056

.056

6800

.098

.098

.098

.098

.068

.068

.068

0.49

.049

.039

.039

.039

.039

.039

.039

.039

10000

.066

.066

.066

.066

.046

.046

.046

.033

.033

.027

.027

.027

.027

.027

.027

.027

15000

.044

.044

.044

.044

.031

.031

.031

.022

.022

.018

.018

.018

.018

.018

.018

.018

22000

.030

.030

.030

.030

.021

.021

.021

.015

.015

.012

.012

.012

.012

.012

.012

.012

33000

.020

.020

.020

.020

.014

.014

.014

.010

.010

47000

.014

.014

.014

.014

.010

0.10

.010

56000

.012

.012

.012

.012

68000

.010

.010

.010

.010

MAXIMUM ALLOWABLE ESR (in Ohms) for dipped solid tantalum electrolytics. Based on SENCORE LC102 Capacitor-Inductor Analyzer

Capacity in µF

1.5V

3.0V

6.0V

10V

15V

20V

25V

35V

50V

100V

200V

300V

400V

500V

600V

1000V

1.0

133

133

133

79.6

79.6

79.6

79.6

66.3

66.3

66.3

66.3

66.3

66.3

66.3

66.3

66.3

1.5

88.4

88.4

88.4

53.1

53.1

53.1

53.1

44.2

44.2

44.2

44.2

44.2

44.2

44.2

44.2

44.2

2.2

60.3

60.3

60.3

36.2

36.2

36.2

36.2

30.1

30.1

30.1

30.1

30.1

30.1

30.1

30.1

30.1

3.3

40.2

40.2

40.2

24.1

24.1

24.1

24.1

20.1

20.1

20.1

20.1

20.1

20.1

20.1

20.1

20.1

4.7

28.2

28.2

28.2

16.9

16.9

16.9

16.9

14.1

14.1

14.1

14.1

14.1

14.1

14.2

14.1

14.1

6.8

19.5

19.5

19.5

11.7

11.7

11.7

11.7

11.7

11.7

11.7

11.7

11.7

11.7

11.7

11.7

11.7

10

13.3

13.3

13.3

7.96

7.96

7.96

7.96

7.96

7.96

7.96

7.96

7.96

7.96

7.96

7.96

7.96

15

8.84

8.84

8.84

5.31

5.31

5.31

5.31

5.31

5.31

5.31

5.31

5.31

5.31

5.31

5.31

5.31

22

6.03

6.03

6.03

3.62

3.62

3.62

3.62

3.62

3.62

3.62

3.62

3.62

3.62

3.62

3.62

3.62

33

4.02

4.02

4.02

2.41

2.41

2.41

2.41

2.41

2.41

2.41

2.41

2.41

2.41

2.41

2.41

2.41

47

2.82

2.82

2.82

1.69

1.69

1.69

1.69

1.69

1.69

1.69

1.69

1.69

1.69

1.69

1.69

1.69

68

1.95

1.95

1.95

1.17

1.17

1.17

1.17

1.17

1.17

1.17

1.17

1.17

1.17

1.17

1.17

1.17

100

1.33

1.33

1.33

0.80

0.80

0.80

0.80

0.80

0.80

0.80

0.80

0.80

0.80

0.80

0.80

0.80

150

0.88

0.88

0.88

0.88

0.88

0.88

0.88

0.53

0.53

0.53

0.53

0.53

0.53

0.53

0.53

0.53

220

0.60

0.60

0.60

0.60

0.60

0.60

0.60

0.36

0.36

0.36

0.36

0.36

0.36

0.36

0.36

0.36

330

0.40

0.40

0.40

0.40

0.40

0.40

0.40

0.24

0.24

0.24

0.24

0.24

0.24

0.24

0.24

0.24

470

0.28

0.28

0.28

0.28

0.28

0.28

0.28

0.17

0.17

0.17

0.17

0.17

0.17

0.17

0.17

0.17

680

0.20

0.20

0.20

0.20

0.20

0.20

0.20

0.12

0.12

0.12

0.12

0.12

0.12

0.12

0.12

0.12

1000

0.13

0.13

0.13

0.13

0.13

0.13

0.13

0.08

0.08

0.08

0.08

0.08

0.08

0.08

0.08

0.08

1500

0.09

0.09

0.09

0.09

0.09

0.09

0.09

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

0.05

2200

0.06

0.06

0.06

0.06

0.06

0.06

0.06

0.04

0.04

0.04

0.04

0.04

0.04

0.04

0.04

0.04

3300

0.04

0.04

0.04

0.04

0.04

0.04

0.04

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

4700

0.03

0.03

0.03

0.03

0.03

0.03

0.03

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.02

6800

0.02

0.02

0.02

0.02

0.02

0.02

0.02

0.01

0.01

0.01

0.01

0.01

0.01

0.01

0.01

0.01

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