DIGITAL AMMETERDIGITAL AMMETER

A Mini Project PRESENTATION

on                                                                  By

P. ANIL KUMAR (12B95A0413)   

INTERNAL GUIDE PROJECT CO-ORDINATOR Ms. KIRAN MAYE                                                             Md. SHOUKATH ALI (Assistant Professor) (Associate Professor) 

 

INTRODUCTION• An ammeter is a measuring instrument used to measure the electric current in a circuit.

An ammeter is a measuring instrument used to measure the electric current in a circuit.

Electric currents are measured in amperes (A), hence the name. Instruments used to

measure smaller currents, in the mill ampere or microampere range, are designated as

milli ammeters or micro ammeters. Early ammeters were laboratory instruments which

relied on the Earth's magnetic field for operation. By the late 19th century, improved

instruments were designed which could be mounted in any position and allowed

accurate measurements in electric power systems. Current is the measure of the rate of

electron "flow" in a circuit. It is measured in the unit of the Ampere, simply called

"Amp," (A).

History The relation between electric current, magnetic fields and physical

forces was first noted by Hans Christian orsted.

who, in 1820, observed a compass needle was deflected from pointing North when a current flowed in an adjacent wire.

Frist ammeter

CONSTRUCTION:

This project mainly consists of following:1.AT89S52 (microcontroller)

2.ADC 0804 (A/D converter)

3.Load

4.LCD 16*2 (LCD display)

5.Keypad

6.LEDs

7.Crystal oscillator (11.0592 MHz)

8.12V Relay

9.Step down transformer

10.Diodes

11.Voltage regulators (7805,7812)

12.Push button switches

13.Fixed and variable resistors, capacitors

14.Connectors

Block Block diagradiagram of m of

AT89S5AT89S52 2 (MICRO (MICRO CONTROLLCONTROLL

ER)ER)

Block diagram of ADC0804:

LCD DIAGRAM:• LCDs are used in a wide range of applications including computer monitors

televisions,  instrument panels, aircraft cockpit displays, and signage. 

• The LCD screen is more energy efficient and can be disposed of more safely than a CRT.• Its low electrical power consumption enables it to be used in battery  powered                 

electronic equipment.

• Liquid crystals were first discovered in 1888

An LED display is a flat panel display, which uses an array of light-emitting diodes as pixels for a video display. Their brightness allows them to be used outdoors in store signs and billboards, and in recent years they have also become commonly used in destination signs on public transport vehicles

LED’s : LED’s :

A light-emitting diode (LED) is a two-lead semiconductor light source. It is a PN-junction diode, which emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor.

Led figure

WORKING:

•In this project we have used ADC0804 for measuring dc current and it coverts this analog quantity into binary form and microcontroller is used for properly measuring the binary data and display it ON the LCD screen.

• We have made three loads which consumes different power and these loads are made of LEDs and we connected these load in parallel we connected them to source and we set a power consumption limit and when this limit reached then screen displays overloading. •It turns OFF the power supply and then keypad security system turns ON and it will turn ON the power supply if the user enter the correct password and if the password is wrong then the power supply remains in OFF state.

•Microcontrollers usually don’t have specific ports for measuring currents, but they do have ADC channels through which you can measure analog voltages of a certain range. This means a dc current can be indirectly measured by a microcontroller’s ADC channel by first converting the current into voltage. The simplest way of doing this is to place a resistance in series with the current path and measure the voltage drop across it. But hold on, if you place an additional resistance in the circuit, it will affect the original current. Therefore, we need to use a very small value resistance so that it’s effect in the circuit current won’t be significant.

Types of ammeter

 Moving-coil ammeters Electrodynamic ammeters

Moving-iron ammeters Hot-wire ammeters Digital ammeters Integrating ammeters

Moving-coil ammeters It uses magnetic deflection, where current passing through a coil causes the coil to move in a magnetic field.

Electrodynamic ammetersAn electrodynamic movement uses an electromagnet instead of the permanent magnet of the d'Arsonval movement.

Moving-iron ammeters

Moving iron ammeters use a piece of iron which moves when acted upon by the electromagnetic force of a fixed coil of wire

Hot-wire ammeters

In a hot-wire ammeter, a current passes through a wire which expands as it heats

Digital ammetersDigital ammeter designs use a shunt resistor to produce a calibrated voltage proportional to the current flowing.

Integrating ammetersIn these ammeters the current is summed over time, giving as a result the product of current and time; which is proportional to the energy transferred with that current.

ADVANTAGES :

  

1. They are more accurate than analog multimeters.

2. They reduce reading and interpolation errors.

3. The 'auto-polarity' function can prevent problems from connecting the

meter to a test circuit with the wrong polarity.

4. Parallax errors are eliminated. If the pointer of an analog multimeter

is viewed from a different angle, you will see a different value. This is

parallax error. A digital multimeter's numerical display solves this

problem

5 Digital multimeter displays have no moving parts. This makes them

free from wear and shock failures.

6.The reading speed is increased as it is easier to read.

7. Unlike analog multimeters, zero adjustment is not required.

DISADVANTAGES : 

1.The LCD display depends on a battery or external power source.

When the battery is low, the display will be dim, making it difficult to

read.

2.In case of fluctuations or transients, it can record an error.

3.Warming of the meter during its use can change its properties

leading to errors in measured value.

4.The A/D converter has a limitation on word length which can cause

quantization noise giving rise to error in measured value.

5.There is a voltage limitation. If it is increased beyond the limit, the

meter will be damaged.

6.The digital nature makes it unsuitable for adjusting tuning circuits or

peaking tunable responses.

7.They are expensive due to high manufacturing cost.

Features: Many digital ammeters provide special measurement types or advanced options or features.  Adjustable sampling rate - The sampling rate is manually adjustable.Alarm LED - Alarm light-emitting diodes (LEDs) light when the RMS value or peak value is greater than the range. Typically, alarm LEDs light only when the range has been greatly exceeded.Application software - The device has embedded application software.Auto-Ranging - Auto-ranging devices are self-adjusting to offer the best measurement scenario.Battery powered - Devices are battery-powered.Data acquisition - Devices with data acquisition capabilities have a computer interface and software for uploading data.Data storage / logging - Data storage or data logging devices have internal memory for storing data.dB readings - Devices measure values in decibels (dB).External shunts - External shunts can be used to extend the current input range. For example, an input that exceeds 5 A can be measured by providing a shunt.

Filters - Devices have embedded filters.Integrating functions - Integrating functions allow the active power and current to be integrated (Wh and Ah).Mirrored scale - Mirrored scales make it easier to read the instrument to a given accuracy by enabling the operator to avoid parallax errors.Overload protection - Devices with overload protection have fuses or other devices to protect the meter.Programmable - Programmable devices can be programmed with trigger values to perform measurements.Range switch - Range switches can be used to select an appropriate range of units to be measured.Removable data storage - Devices with removable data storage have removable memory, drives, etc.Scaling function - Devices with a scaling function allow the pre-setting of the potential transformer and current transformer ratio, and the power scaling factor.Temperature compensated - Temperature-compensated devices are designed to counteract known errors caused by temperature changes.Triggering - Devices with triggering have an interface for external triggering.