Capacitor ESR Tester
the good, the bad and the leaky…
Published in issue 313, September 2002
How about an in-circuit capacitor tester to take the strain out of tracking down faulty capacitors? No need to solder out any capacitor, simply check it in-circuit, from thousands of microFarads down to a hundred nanoFarads. In most cases, parallel coils or low value resistors are no problem. Even shorted caps may be revealed in-circuit and polarity is irrelevant for the tester. High ESR? Replace!The most significant property of a capacitor is its capacitance but besides that there’s another important factor, namely the so called ESR, or Equivalent Series Resistance. An ideal capacitor is a purely reactive component with a 90-degree phase angle between current and voltage. In the real world, however, a capacitor needs to be modelled as an ideal capacitor in series with a resistor representing the losses introduced by the component.
Resistors:
R1,R13,R14,R17,R18,R19,R31 = 10kOhm
R2 = 4kOhm 7
R3 = 1kOhm 8
R4,R24,R28 = 22kOhm
R5 = 33kOhm
R6,R7,R8 = 2kOhm 2
R9-R12 = 56Ohm
R15,R16,R20,R22,R29 = 1MOhm
R21 = 47Ohm
R23,R25,R27,R30 = 100kOhm
R26 = 1kOhm
P1,P4 = 5kOhm multiturn preset, vertical mounting, side adjust (Bourns 3266X, Farnell #347-747)
P2 = 100kOhm multiturn preset, vertical mounting, side adjust (Bourns 3266X, Farnell #347-784)
P5 = 1kOhm multiturn preset, vertical mounting, side adjust (Bourns 3266X, Farnell #347-723)
P3 = 1kOhm preset, horizontal mounting
Capacitors:
C1 = 180pF
C2,C9-C13,C16,C18 = 100nF
C3,C4,C5 = 10µ F 10V radial
C6 = 100µ F 16V radial
C7 = 220nF
C8 = 10nF
C14=100pF
C15 = 1nF
C17 = 220nF
Semiconductors:
D1-D4 = 1N4002
IC1 = 4093
IC2 = 74ACT74 PC
IC3 = 74VHC4066
IC4 = LF412-CN
IC5 = LM2931-5,0
IC6 = 4070
IC7 = ICL7660
IC8 = LM358-N
IC9 = ICL7106-CP
Miscellaneous:
LCD1 = 3.5 Digit LCD with LO-BATT indicator, e.g., Varitronix VI-302 DPRC (Farnell #478-660)
S1 = pushbutton, 1 make contact
Battery holder
On/off switch
2 miniature probes, e.g., Hirschmann PRUF1 (Farnell #523-483)
Length of 2-core screened cable
ABS enclosure with LCD window and battery compartment, e.g. Multicomp type BC4, (Farnell # 645-758)
40-pin IC socket cut in half (see text)
PCB, order code 012022-1
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Click below to download a PDF copy of this article from Elektor magazine. Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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