In this note, we are going to know about Vector Impedance Meter and also the Block Diagram of Vector Impedance Meter. Welcome to Poly Notes Hub, a leading destination for engineering notes.
Author Name: Arun Paul.
What is Vector Impedance Meter?
A Vector Impedance Meter is an electrical device that measures the impedance of a circuit or component across a variety of frequencies. Unlike traditional impedance meters, it gives magnitude and phase information, enabling for a thorough assessment of impedance in complex circuits.
📌 Specifications of Vector Impedance Meter
- The frequency ranges from Hz to GHz.
- The impedance ranges from milliohms to megaohms.
- The accuracy is ±0.1% to ±1% depending on the model.
- It has the digital display which shows the correct data.
- The interface is USB, GPIB, or Ethernet for remote control and data logging.
Block Diagram of Vector Impedance Meter
Here is the vector impedance meter block diagram and the description of each section of the meter –
The block diagram of the Vector Impedance Meter consists of various components that help in measuring impedance (both magnitude and phase angle) of an unknown impedance Zx. Here’s a step-by-step explanation of how it works:
- AC Supply & Transformer: An AC supply is used as the input excitation. A transformer is employed to isolate and step up/down the AC signal.
- Series Resistor (Rs) and Unknown Impedance (Zx): The unknown impedance Zx is placed in series with a known resistor Rs. This configuration helps in measuring the voltage drop across Zx and Rs, which is crucial in impedance calculation.
- Balanced Isolating Amplifiers: Two balanced isolating amplifiers are used to ensure proper signal conditioning. These amplifiers isolate different circuit sections while maintaining signal integrity.
- Resistor Network (R1,R2,R3,R4): The resistors in the circuit form a balanced bridge to facilitate impedance measurement. They help in maintaining signal symmetry and ensuring accurate voltage comparison.
- Balanced Rectifier: The rectifier converts the AC signal into a DC signal for further processing. This enables easier measurement of impedance parameters.
- Indicating Meter: The final processed signal is displayed on an indicating meter. The meter shows the impedance magnitude and phase angle, allowing for easy interpretation.
The AC signal passes through the circuit, encountering the unknown impedance Zx. The balanced amplifiers process the signals from different points. The rectifier converts the AC signal into DC. The final reading is displayed on the indicating meter, giving information about the magnitude and phase of Zx.
Vector Impedance Meter Working Principle
A Vector Impedance Meter works by applying an AC test signal to the device under test (DUT) and measuring its impedance. Using an oscillator, the instrument initially generates a sinusoidal signal with a known frequency. This signal is then divided into two paths: one as a reference signal and the other for application to the DUT. The measuring bridge or network compares the applied voltage to the current flowing through the DUT, recording magnitude and phase information.
A detector circuit detects voltage and current signals, which are then processed by a phase detector to determine the phase difference between them. The impedance (Z) is computed by the formula –
where;
- V = Voltage across the DUT
- I = Current flowing rate
- R = Resistance
- X = Reactance
An analog-to-digital converter (ADC) converts the measured data into digital representation, which is subsequently processed by a microcontroller or processor. Finally, the impedance magnitude, phase angle, and other characteristics are displayed on the screen to the user.
Applications of Vector Impedance Meter
Here are the list of application of vector impedance meter –
- Used in RF and microwave applications to measure impedance and phase response.
- Used to characterizes inductors, capacitors, and resistors over a frequency range.
- Used to ensures correct impedance matching in communication circuits.
- Used for bio-impedance measurements in medical diagnostics.
- Used for measuring impedance in transformers, motors, and power circuits.