Category: MEASURING INSTRUMENTS

A digital multimeter (DMM) displays the AC or DC voltages being measured directly as discrete numerals in the decimal number system. Numerical readout of DMM is very convenient and it eliminates observational error. The use of digital multimeters increases the speed with which the readings can be taken. The DMM is a versatile and accurate instrument used…

These instruments are very sensitive and accurate. These can be used only on DC as voltmeter and ammeter. The pictorial view of a voltmeter and ammeter is shown in Figures 9.19 and 9.20, respectively. The scale of such instruments is uniform, as shown in the Figure 9.20. Fig. 9.19  Voltmeter Fig. 9.20  Ammeter 9.9.1  Principle The basic principle of permanent magnet-type moving…

These instruments are quite cheap in cost, simple in construction, and reasonably accurate at fixed power supply frequency. These instruments can be used both on AC and DC. Therefore, these are widely used in laboratories and on switching panels. These instruments are used either as voltmeter or ammeter only. The pictorial view of these instruments is…

The errors that are common to all types of instruments are given as follows:

Measurement is essentially an act by which a comparison is made between a given quantity and a quantity of the same kind chosen as a unit of measurement, that is, standard quantity. To make this comparison, a device is used called measuring instrument. When an unknown quantity is measured, the value thus obtained is considered…

To obtain critical damping (i.e., the value of damping that is sufficient to enable the point to rise quickly to its deflected position without overshooting), adjustments are made while designing the instruments. Damping torque or force can be provided by the following methods. 9.5.1  Air Friction Damping Two methods of air friction damping are illustrated in Figure…

The controlling or restoring or balancing torque is provided in the indicating instruments by two methods, namely spring control and gravity control. 9.4.1  Spring Control In this method, two phosphor bronze spiral hair-springs A and B are attached to the moving system (spindle) of the indicating instrument as shown in Figure 9.6(a). However, only one spring is used in moving iron…

In the field of engineering, various types of quantities such as physical, chemical, mechanical, thermal, and electrical are involved. For records, these quantities are required to be measured by different methods using different types of instruments. Electrical measuring instruments are widely used in the modern engineering world because of their accuracy, convenience, and reliability. These…

To measure the magnitude of a quantity, a fixed quantity of that kind is taken as basis, and then, whole quantity is compared with it. The fixed quantity that is taken as basis is called unit and the process of comparing the quantity with this unit is termed as measurement. In other words, measurement means…

In the field of engineering, various types of quantities such as physical, chemical, mechanical, thermal, and electrical are involved. For records, these quantities are required to be measured by different methods using different types of instruments. Electrical measuring instruments are widely used in the modern engineering world because of their accuracy, convenience, and reliability. These…