High R, Wave and Spectrum Analyzers.pptx

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1. Meas. of high Resistance Multimeters Function Generator Wave Analyzers Spectrum Analyzer Q Meter Rahul Katiyar Asst. Prof., Banasthali Vidyapith

2. Why meas. of high resistance is important ? Winding insulation of generators, electrical machines and transformers. Insulation resistance of electrical components. Leakage resistance of capacitors Surface resistivity Volume resistivity of materials .

3. 1. Loss of Charge Method

4. In loss of charge method, the voltage across a capacitor of 0.4343 μ F is 10 V and it is decreased to 1 V in 2 minutes when the switch is opened. Find the value of unknown resistance ?

5. 2. Megaohm Bridge Method

6. 3. Direct Defection Method

7. 4. Megger

8. Multimeters Multimeters are also called multitesters. Multimeters are used to measure voltage (DC/AC), current (DC/AC),and resistance. Main types of multimeters are: Volt-ohm- milliammeter (VOM) [Analog Multimeter] Digital multimeter (DMM) Features of DMM: High accuracy, High input impedance, Low loading error, Small size and elimination of observational, parallax and approximation errors.

9. Types of Multimeter Types of Meters Volt-Ohm- Milliammeter (VOM) [ ANALOG MULTIMETER] Uses a moving pointer and a printed scale to indicate values of voltage, current, or resistance. Allows all three kinds of measurements on a single scale or readout. No power supply, suffer less from electric noise and isolation problems. Simple, Portable and low cost and fair sensitivity of 20K Ω /V. Digital multimeter : Uses a numerical readout to indicate the measured value of voltage, current or resistance. High Durability, Accuracy, Sensitivity, Resolution, Precision.

10. Analog Meter: Ammeter Analog instruments use a moving coil meter movement. Current flow in the coil moves the pointer up- scale . Meter shunts are low-value precision resistors that are connected in parallel with the meter movement in order to increase the range of current.

11. Analog meter: Voltmeters A voltmeter is connected across two points to measure their difference in potential. A multiplier resistor is a large resistance in series with a moving-coil meter movement which allows the meter to measure voltages in a circuit A dc voltmeter must be connected with the correct polarity. Analog voltmeters are rated in terms of the ohms of resistance required for 1 V of deflection. This value is called the ohms-per-volt rating , or the sensitivity of the voltmeter. It is determined by full scale current of meter movement.

12. Analog Meters: Ohmmeters The ohmmeter is a great tool for checking the continuity between two points. When checking for continuity, make sure the ohmmeter is set on the lowest ohms range. If continuity exists between two points, the ohmmeter will read a very low resistance such as zero ohms. If there is no continuity between two points, the ohmmeter will read infinite ohms.

13. Digital Multimeters (DMMs) The digital multimeter has become a very popular test instrument and easier to use. The digital value of the measurement is displayed automatically with decimal point, polarity, and the unit for V, A, or Ω . They eliminate the human error that often occurs in reading different scales on an analog meter with a pointer. They are also being used to measure temperature, frequency, testing of diodes, true rms values, capacitance, conductance, dB. Types: Panel Meter / Bench meter (system meter) They have auto ranging so that range selection is not r equired. Normally 3 and half digit digital display is used.

14. Meter Applications Voltmeter Milliammeter or Ammeter Ohmmeter Power on in circuit Power on in circuit Power off in circuit Connect in parallel Connect in series Connect in parallel High internal R Low internal R Has internal battery Has internal series multipliers; higher R for higher ranges Has internal shunts; lower resistance for higher current ratings Higher battery voltage and more sensitive meter for higher ohms ranges

15. Comparison b/n Analog MM vs Digital MM Analog Multimeter Low cost / Portability/ Do not require outside source of supply. Wrong scales might be used or might be read incorrectly. Pointer attempts to deflects left when terminal polarity is incorrect. Damaged when dropped from bench levels. No such measurements Digital Multimeter Durability/Portability/Accuracy/Precision/Resolution Leaves no doubt about the measured quantity. Indicates negative quantity when terminal polarity is incorrect. No damage Meas. of freq., capacitance, conductance, dB, testing of diodes and transistors, true RMS values possible.

16. FUNCTION GENERATOR

17. Q-Meter Practical Circuit

18. Applications of Q meter Measurement of Effective Resistance Measurement of Inductance Measurement of Bandwidth Measurement of Q (practical) Measurement of Self (Distributed Capacitance )

19. A coil of resistance 10 Ω is connected to the Q meter circuit between terminals T1 and T2. Resonance occurs at a frequency of 1 MHz with the tuning capacitor set to 65 pF. Calculate the percentage error introduced in the calculated value of quality factor if the resistance of 0.02 Ω is used across the oscillator circuit.

20. In the set up for the determination of self capacitance of coil, the standard variable capacitor has a value of 460 pF at 2 MHz. and a value of 100 pF at 4 MHz what is coil’s self capacitance ?

21. Wave Analyzer Any complex waveform is made up of a fundamental and its harmonics . Wave analyzer is used to measure the amplitude of each harmonic or fundamental frequency individually. Wave analyzers are also referred to as frequency selective voltmeters, carrier frequency voltmeters, and selective level voltmeters. The instrument is tuned to the frequency of one component whose amplitude is measured. Some wave analyzers have the automatic frequency control which tunes to the signal automatically.

22. Basic Wave Analyzer

23. The analyzer consists of a primary detector, which is a simple LC circuit . The LC circuit is adjusted for resonance at the frequency of the particular harmonic component to be measured. It passes only the frequency to which it is tuned and provides a high attenuation to all other frequencies. The full wave rectifier is used to get the average value of the input signal. The indicating device is a simple dc voltmeter that is calibrated to read the peak value of the sinusoidal input voltage. Working process for wave analyzer

24. Applications Amplitude measurement of a single component of a complex waveform. Amplitude measurement in the presence of noise and interfering signals. Measurement of signal energy within a well-defined bandwidth. Industrially in the field of reduction of sound and vibrations generated by the rotating machinery. Used in Harmonic analysis.  

25. Spectrum Analyzer Spectrum Analysis is defined as the study of energy distribution across the frequency spectrum of a given electrical signal. The study gives valuable information about bandwidth, effects of different types of modulation and signal generation. Analysis of the spectrum of frequency domain of a signal is called spectrum analysis. They usually display raw, unprocessed signal information like voltage, power, period, waveshapes , sideband and frequency. Most common Spectrum Analyzer Measurements : Modulation, Noise, Distortion. Can easily measure low amplitudes and high frequency. Operating range : 0.02 Hz to 250 GHz.

26. Applications Finding intermodulation content, FM Deviation, pulse width and repetition rate. Measurement of frequency and its response. Analyzing modulated signals. Finding Bandwidth and studying harmonic components. Antenna Patterns, AF And RF Analysis.