Successive Approximation Type DVM Block Diagram | Working | New Topic

In this note, we are going to know about Successive Approximation Type DVM Block Diagram and Its Working Principle. Welcome to Poly Notes Hub, a leading destination for electrical engineering notes.

Author Name: Arun Paul.

What is Successive Approximation Type DVM?

A Successive Approximation Type Digital Voltmeter (DVM) is a precise and efficient voltage measurement instrument that converts an analog voltage signal into a digital output using the Successive Approximation Register (SAR) ADC technology.

Specifications of Successive Approximation Type DVM

• The measurement range is typically from millivolts to several volts.
• The resolution is high from 16 to 24 bits.
• The accuracy is also high (around ±0.005% to ±0.01%)
• Power consumption is low as compare to Ramp Type DVM.
• The input impedance is usually very high to avoid loading effects.

Successive Approximation Type DVM Block Diagram

Here is the block diagram of Successive Approximation Type DVM –

• Input Attenuator: This component decreases the amplitude of the input voltage to within the DVM’s detectable range. It prevents high voltage signals from damaging the internal circuitry.
• Sample and Hold Circuit: This circuit catches and maintains the input voltage at a steady level throughout the conversion process, eliminating fluctuations and assuring reliable measurements.
• Comparator: It compares the input voltage (Vin) to the output voltage (Vout) of the Digital-to-Analog Converter (DAC). If Vin exceeds Vout, the comparator produces a high signal; otherwise, it remains low.
• Digital to Analog Converter: This portion translates the control register’s digital output to an equivalent analog voltage, which is then compared to the input voltage.
• Reference Voltage: Provides a constant reference voltage to the DAC, allowing for accurate digital-to-analog conversion.
• Control Register: This register stores the digital value obtained by the successive approximation procedure. It adjusts the binary output to match the input voltage using comparator feedback.
• Gate: Acts as a controller, allowing or blocking signals between sections and ensuring that actions are performed sequentially.
• Ring Counter: Creates clock pulses that drive the control register and govern the step-by-step approximation process.
• Start and Stop Mechanism: This section begins and ends the conversion process. When the start signal is delivered, the measurement begins, and the procedure ends when the digital output is received.
• Delay Circuit: Introduces essential timing delays to guarantee that processes are performed in the correct order, preventing voltage measurement mistakes.
• Digital Output: This is the conversion’s final result, presented in binary or decimal format, and represents the measured voltage.

Example: Conversion of 5.2V (Analog Input) using a 4-bit SAR ADC (Reference Voltage = 10V)

Here is an example of an Output Table for a Successive Approximation Type DVM, demonstrating the step-by-step approximation method for converting an analog input voltage to a digital output.

Final Digital Output: 010100 (Equivalent to 5.125V in decimal form)

This table demonstrates the operation of the Successive Approximation Register (SAR) ADC, in which the comparator continually checks and changes the digital output until it nearly matches the input voltage.

Successive Approximation Type DVM Working Principle

Below we have describe the working of Successive Approximation Type DVM –

The Successive Approximation Register (SAR) ADC technology is used in Successive Approximation Type Digital Voltmeters (DVMs). The process begins by comparing the input analog signal to a reference voltage using a comparator. A Successive Approximation Register (SAR) sets the Most Significant Bit (MSB) to 1, which is then transformed into an equivalent analog voltage by a Digital-to-Analog Converter (DAC). The comparator then determines if the DAC output is higher or lower than the input voltage. If the DAC output is less than or equal to the input voltage, the bit remains at one; otherwise, it is reset to zero.

This technique is repeated for each bit, from MSB to Least Significant Bit (LSB), until the digital equivalent of the input voltage is calculated. The resulting binary value is then translated to numerical format and shown on the DVM screen. This approach enables rapid and precise digital voltage measurement, making successive approximation DVMs popular in digital multimeters, automatic test equipment, industrial control systems, and medical instruments. Their fast speed, accuracy, and low power consumption make them an excellent choice for applications that require precise voltage readings.

Successive Approximation Type DVM Advantages

Here we have listed some advantages of successive approximation type DVM –

• This instrument faster than Ramp Type DVM and Integrating Type DVM.
• It is provides precise measurements with low error. So, have high accuracy.
• This device consumes low power than other voltmeters.
• It requires fewer components, making it suitable for portable devices.
• This device can measures both AC and DC voltages accurately.

Successive Approximation Type DVM Applications

Here we have listed some applications of successive approximation type DVM –

• Used in digital multimeters (DMM) for high accuracy voltage measurements.
• Used in automatic test equipment for electronic circuit testing.
• Used in oscilloscopes and data acquisition systems.
• Used in medical devices, such as ECG and EEG monitors.
• Also used in industrial process control systems for monitoring voltage variations.