Design And Construction Of An Analogue Capacitance Meter

ABSTRACT

There has always been a problem identifying capacitors, due to the enormous variety in size, shape and coding. Most of the time it is impossible to identify them by size due to the different forms of construction. So you have to be able to read and interpret the codes on the body. But if the numbers are missing or microscopic in size, you have a problem. The only solution is to have a piece of test equipment to identify them for you.

A capacitance meter is a piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors. Depending on the sophistication of the meter, it may display the capacitance only, or it may also measure a number of other parameters such as leakage, equivalent series resistance (ESR), and inductance.

This device reads the value of a capacitor and displays it on an analogue meter.

CHAPTER ONE

INTRODUCTION

A capacitance meter is a piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors. Depending on the sophistication of the meter, it may display the capacitance only, or it may also measure a number of other parameters such as leakage, equivalent series resistance (ESR), and inductance. For most purposes and in most cases the capacitor must be disconnected from circuit; ESR can usually be measured in circuit.

Some checks can be made without a specialized instrument, particularly on aluminium electrolytic capacitors which tend to be of high capacitance and to be subject to poor leakage. A multimeter in a resistance range can detect a short-circuited capacitor (very low resistance) or one with very high leakage (high resistance, but lower than it should be; an ideal capacitor has infinite DC resistance). A crude idea of the capacitance can be derived with an analog multimeter in a high resistance range by observing the needle when first connected; current will flow to charge the capacitor and the needle will “kick” from infinite indicated resistance to a relatively low value, and then drift up to infinity. The amplitude of the kick is an indication of capacitance. Interpreting results requires some experience, or comparison with a good capacitor, and depends upon the particular meter and range used.

More sophisticated instruments use other techniques such as inserting the capacitor-under-test into a bridge circuit. By varying the values of the other legs in the bridge (so as to bring the bridge into balance), the value of the unknown capacitor is determined. This method of indirect uses of measuring capacitance ensures greater precision. The bridge usually can also measure series resistance and inductance. Through the use of Kelvin connections and other careful design techniques, these instruments can usually measure capacitors over a range from picofarads to farads. Combined LCR meters that can measure inductance, resistance, and capacitance are available.

Bridge circuits do not themselves measure leakage current, but a DC bias voltage can be applied and the leakage measured directly.

Modern bridge instruments usually include a digital display and, where relevant, some sort of go/no go testing to allow simple automated use in a production environment. As with all modern instruments, bridges can be interfaced to computer and other equipment to export readings and allow external control.

Equivalent series resistance

While not a capacitance meter as such, a dedicated ESR meter will measure the equivalent series resistance (but not the capacitance) of a capacitor without the need to disconnect it from circuit. Capacitors which cause circuit failure due to high ESR with capacity within tolerance, particularly in switch-mode power supplies, are common.

1.2                                             OBJECTIVE OF THE PROJECT

The objective of this project is construct an electronic testing equipment used to measure capacitance, mainly of discrete capacitors.

1.3                                         SIGNIFICANCE OF THE PROJECT

There has always been a problem identifying capacitors, due to the enormous variety in size, shape and coding. Most of the time it is impossible to identify them by size due to the different forms of construction. So you have to be able to read and interpret the codes on the body. But if the numbers are missing or microscopic in size, you have a problem. The only solution is to have a piece of test equipment- capacitance meter, to identify them for you.

1.4                                                 SCOPE OF THE PROJECT

This project is capable of measuring all but the largest capacitors used in circuits. As well, the markings of capacitors from salvaged equipment often rub off. By being able to measure these unmarked components, this project will prove useful to the constructor, vintage radio enthusiast or antenna experimenter.

1.5                                              PURPOSE OF THE PROJECT

The purpose of this work is to design a piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors. Depending on the sophistication of the meter, it displays the capacitance of capacitors only

1.6                                              PROBLEM OF THE PROJECT

• Results might not be accurate.
• For accurate results, it is suggested to go for DMMs which can measure capacitance.

1.7                                                      APPLICATIONS OF THE PROJECT

• Capacitance Meter can be used to measure capacitance of unknown capacitors.
• Using Arduino for Capacitance Meter makes it easy to implement the project and with slight modifications, the circuit can be made for a wide range of capacitors.

1.7                          PROJECT WORK ORGANIZATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to the study. In this chapter, the background, significance, objective, purpose, scope, application, limitation and problem of the study were discussed.

Chapter two is on literature review of this study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.