IEEE 120:1989 pdf download.IEEE Master Test Guide for Electrical Measurements in Power Circuits.
The methods given here relate to measurements, as made with either analog or digital indicating or integrating instruments, of power, energy, voltage, and current, in de or ac rotating machines. transformers, induction apparatus, arc and resistance heating equipment, mercury arc, thermionic, or solid-state rectifiers and inverters. Measurements made with supplementary instruments and devices are also included. This guide does not deal with measurements of resistance or temperature that are often included in determining the performance characteristics of electric machinery. Instrumenis for these latter measurements will he found in the specific publications dealing with the particular measurement, such as IEEE Std 118-1978, IEEE Standard Test Code for Resistance Measurements 1411, and IEEE Sd 119-1974, IEEE Reconimended Practice for General Principles of Temperature Measurement as Applied to Electrical Apparatus 151.
1.3 Units
The measurement of any electrical quantity is the comparison of that quantity with another quantity of the same kind that has been chosen as a unit. The fundamental or basic electrical units are based on the International System of Units (SI). which is a modern version of the MKSA (meter, kilogram. second, ampere) system. For further details see ansi ieee 268-1982, IEEE Standard for Metric Practice [3]. In magnetic measurements it is the common practice to use the cgs (centimeter-gram-second) system. The instrument readouts are frequently in the cgs units. Hence, in Chapter 6 of this guide both units are used and a conversion table is provided.
This is normally done using a capacitor-type integrator. A wide variety of both passive and active circuits is in use. Since the integral of a symmetrical alternating signal (over one period) is zero, the averaging circuit gives only the dc component of the waveform.
1.6.2 Measurement of Average Absolute Value
The average absolute value (MV) is a more useful parameter that is obtained by rectifying the signal before integration. Circuits ranging from simple diode bridges to operational-amplifier-aided rectifiers and integrators are commonly used in analog and digital indicating instruments.
The scales of such instruments can be, and are, usually marked to indicate the rms value of a sinusoidal signal. With sinusoidal waveforms, accuracies of about 0.1—1.0% can be achieved in the measurement of the rms values. With nonsinusoidal waveforms, the errors can be large.
1.6.3 Measurement of Peak Value and Quasi-Peak Value
Peak reading instruments indicate the maximum value of a wavefbrm during a given measurement period. The peak value is obtained by rectifying the signal and storing its maximum value on a capacitor. This value is sensed, without appreciably discharging the capacitor, with a high-impedance averaging voltmeter.
If the capacitor is coupled with a charging resistor and a discharging resistor, a type of quasi-peak-sensing circuit is obtained. if both the charging and discharging time constants are long in relation to the period of the signal to he measured, the response of the quasi-peak circuit is independent of the signal frequency. By adjusting the ratio of the two resistors, any value of rectified periodic signal can he sensed—from its peak value to a value that approaches zero.IEEE 120 pdf download.