1.0 Introduction
The measurement helps in the discovering of size, length or amount of particular quantities. In other words there are different measuring devices used in laboratory such as thermometer, voltmeter etc
This project deals on digital voltmeter. A voltmeter is an electronic devices used in the measurement of voltages. A voltmeter can be grouped into two namely: digital and analogue voltmeter.
The digital voltmeter makes use of an analogue to digital converter. These convert the analogue to digital or convert the analogue voltages to binary form. The binary is sent to the decoder, where it is converted to a seven-segment display.
There are several methods by which the readings of a digital instrument can be displayed but the two main types are the LED (light emitting diode) and LCD (liquid cryptal display). Both units consist of seven segments. The LED display devices require more current than the LCDs and so they consume more power.
They are widely used in bench digital voltmeters (DVMS) where power consumption is not a primary consideration. This project consists of developing a digital voltmeter that can solve the problem of abnormalities in measurement by providing an effective output. The design specification of the DVM are expected to have namely;
- Voltage regulator
- Variable resistors
- (ADC) converter
- Microcontroller
- Decoder (BCD)
- A display
- A probes
The digital voltmeter is grouped according to the type of conversion such as:
- Ramp type
- Continuous balance
- Successive-approximation
- Integrating
An ADC analogue to digital converter) is also known as a dual slope converter or integrating converter. This type of converter is generally preferred over other types because it offers accuracy simplicity in design and a relatively indifference to noise which makes it very reliable. A ramp A/D converter works very much like the counter-ramp. (Continuous balance dvm). The difficulty with ramp-type A/D converter is the long time it takes to count up to higher voltages but the successive approximation A/D converter cuts down the conversion time. The advantages of the successive-approximation are that the digitizing process is faster.
Advantages of the Digital Meter
- The numerical display of the digital meter eliminates parallel
- Errors associated with human reading and interpolation are reduced
- Digital instruments have automatic range and polarity selection and this reduces the need for training its operators on the usage.
- Digital instruments provide output in digital form suitable for further processing, recording or interfacing with computer, printer etc
- Finally, accuracy in digital meter is better as readings are often correct to within +0.1% and -0.1% of the true value, while the analogue type may have an error as large as +10%
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