IEEE 488 BUS: The purpose of IEEE 488 BUS is to provide digital interfacing between program­mable instruments. There are many instrumentation systems in which interac­tive instruments, under the command of a central controller, provide superior error-free results when compared with conventional manually operated sys­tems. Problems such as impedance mismatch, obtaining cables with proper connectors and […]

Microprocessor Based Instruments

Microprocessor Based Instruments: Microprocessor Based Instruments – Digital instruments are designed around digital logic circuits without memory. The use of microprocessors as an integral part of measuring instruments has given rise to a whole new class of instruments, called intelligent instruments. Figure 6.28 shows a block diagram of a microprocessor based impedance measuring instrument. The […]

Digital Capacitance Meter

Digital Capacitance Meter: Digital Capacitance Meter – Since the capacitance is linearly proportional to the time constant, when a capacitor is charged by a constant current source and discharged through a fixed resistance, we can use a 555 timer along with some digital test equipment to measure capacitances. One obvious way is to measure the […]

Automation in Digital Instruments

Automation in Digital Instruments: Automation in Digital Instruments – One of the advantages of digital multimeters is their ease of operation. The reading is easy to take and does not lend itself to errors of interpretation. Moreover, the number of ranges is limited because the ranges move in steps of 10 (instead of the √10 […]

Digital Measurements of Frequency Mains

Digital Measurements of Frequency Mains: Digital Measurements of Frequency Mains – The conventional method of measuring the frequency of an electrical signal consists of counting the number of cycles of the input electrical signal during a specified gate interval. The length of the gate interval decides the resolution of the measurement. The shorter the gate […]

Electronic Counter

Electronic Counter: Electronic Counter – The decade counter can be easily incorporated in a commercial test instrument called an electronic counter. A decade counter, by itself, behaves as a totaliser by totalling the pulses applied to it during the time interval that a gate pulse is present. Typical modes of operation are totalising, frequency, period, […]

Universal Counter Timer

Universal Counter: All measurements of time period and frequency by various circuits can be assembled together to form one complete block, called a Universal Counter Timer. The universal counter uses logic gates which are selected and controlled by a single front panel switch, known as the function switch. A simplified block diagram is shown in […]

Digital Measurement of Time

Digital Measurement of Time: The Principle of Operation of Digital Measurement of Time is given by The beginning of the time period is the start pulse originating from input 1, and the end of the time period is the stop pulse coming from input 2. The oscillator runs continuously, but the oscillator pulses reach the […]

Digital Frequency Meter

Digital Frequency Meter: The Principle of Operation of Digital Frequency Meter is given by The signal waveform is converted to trigger pulses and applied continuously to an AND gate, as shown in Fig. 6.4. A pulse of 1 s is applied to the other terminal, and the number of pulses counted during this period indicates […]

Digital Multimeters

Digital Multimeters: Digital Multimeters – Analog meters require no power supply, they give a better visual indication of changes and suffer less from electric noise and isolation problems. These meters are simple and inexpensive. Digital meters, on the other hand, offer high accuracy, have a high input impedance and are smaller in size. They gives […]

Digital Instruments

Digital Instruments: Digital instruments are rapidly replacing their analog counterparts. The parameters of interest in a laboratory environment are (i) voltage (ii) current (iii) power (iv) frequency, and (v) logic. We shall consider digital systems which measure the above parameters. To enable digital systems to recognise information, inputs which are analog in nature must be […]