Maimaitar Zoginka Tsawon Tsuru

Impedance, wanda ya fi amfani da haka da yawan gaba da tushen jiki, ana iya zama mai muhimmanci ga tsarin kudin kudin a cikin tsakirin AC tare da voltage.

An samar da Vector Impedance Meter don bincike da tsari da kuma tushen jiki na impedance (Z).

Babban lokaci, a wasu hanyoyin bincike da impedance, an samar da asashe na resistance da reactance a cikin rectangular form. Yana nufin

Amma a nan, za a iya samun impedance a cikin polar form. Yana nufin |Z| da kuma tushen jiki (θ) na impedance za a iya samun shi daga wannan meter. A cikin wannan takarda.

An samar da biyu na resistors da masu resistance sama. An samar da voltage drop a cikin RAB ita ce EAB da kuma RBC ita ce EBC. Duk asashe suna duka sama da kuma ita ce na farko da input voltage (EAC).

An samar da variable standard resistance (RST) a cikin series da impedance (ZX) wanda za a iya samun shi.

An samar da equal deflection method don binciken tsarin unknown impedance.

Wannan yana nufin da ake magance voltage drops sama a cikin variable resistor da kuma impedance (EAD = ECD) da kuma evaluating the calibrated standard resistor (here it is RST) wanda take da buƙata don magance shi.

Tushen jiki na impedance (θ) za a iya samun shi daga taking the voltage reading across BD. Wanda ita ce EBD.

Meter deflection zai canza saboda Q factor (quality factor) na connected unknown impedance.

Vacuum Tube Voltmeter (VTVM) tafiya ta yi AC voltage wanda yake canza daga 0V zuwa maximum value. Idan voltage reading ya zama zero, za a iya samun Q zero da kuma tushen jiki ya zama 0o.

Idan voltage reading ya zama maximum value, za a iya samun Q infinite da kuma tushen jiki ya zama 90o.

Angle between EAB and EAD zai zama equal to θ/2 (half of the phase angle of the unknown impedance). Wannan yana nufin saboda EAD = EDC.

Muna son sanin cewa voltage across A and B (EAB) zai zama equal to half of the voltage across A and C (EAC which is the input voltage). Reading of voltmeter, EDB can be thus obtained in terms of θ/2. Hence, θ (phase angle) can be determined. The vector diagram is shown below.

For obtaining the first approximation of the magnitude and phase angle of the impedance, this method is preferred. For achieving more accuracy in measurement the commercial vector impedance meter is preferred.

Commercial Vector Impedance Meter

Impedance can be straight away measured by using a commercial vector impedance meter in polar form. Only a single balancing control is used in this for getting both the phase angle and magnitude of the impedance.

This method can be used to determine any combination of resistance (R), Capacitance (C), and Inductance (L). In addition to this, it can measure complex impedances rather than pure elements (C, L, or R).

The main disadvantage in conventional bridge circuits like too many consecutive adjustments is eliminated here. The range of measurements of impedance is 0.5 to 100,000Ω over the range of frequency 30 Hz to 40 kHz when an external oscillator is used for giving the supply.

The frequencies generated internally are 1 kHz or 400 Hz or 60 Hz and externally up to 20 kHz. The accuracy in readings of the magnitude of the impedance is ± 1% and for the phase angle, it will be ± 2%.

The circuit for the measurement of the magnitude of the impedance is shown below.

Here, for the magnitude measurement, RX is the variable resistor and it can be altered with calibrating impedance dial.

The voltage drops of both the variable resistor and the unknown impedance (ZX) are made equal by adjusting this dial. Every voltage drop is made amplified by using the two modules of balanced amplifiers.

This is then given to the section of the connected dual rectifier. In this, the arithmetical sum of the outputs of the rectifier can be obtained as zero and this is shown as the null reading in the indicating meter. Thus, the unknown impedance can be obtained directly from the dial of the variable resistor.

Next, we can see how the phase angle is obtained in this meter. First, the switch is set in the calibration position and the voltage injected is calibrated.

This is done by setting it for getting the full-scale deflection in the VTVM or indicating meter.

After that, the function switch is kept in phase position. In this condition, the function switch will make the output of the balanced amplifier parallel before going to rectification.

Now, the sum total of the AC voltages which is from the amplifiers is definitely a function of the vector difference among the AC voltages on the amplifiers.

The voltage that is rectified as a result of this vector difference is indicated in the indicating meter or DC VTVM. This is actually the measure of the phase angle between the voltage drop across the unknown impedance and variable resistor.

These voltage drops will be the same in magnitude but the phase is different. Hence, the phase angle is obtained by direct reading from this instrument.

The quality factor and dissipation factor can also be calculated from this phase angle if needed.

The circuit diagram for the measurement of phase angle (θ) is shown below.

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