Question

Which of the following is a zero order instrument?

• A. Potentiometer
• B. LVDT
• C. Capacitive transducer
• D. Rota meter

Hint:

Ideal zero-order instruments don't exist in reality because every device has some mass or capacitance, but the potentiometer is the best theoretical approximation used in textbooks.

Answer 1

The Correct Option is A

In measurement systems, instruments are classified by their "order," which describes the mathematical relationship (differential equation) between the input and the output. 1. Zero-Order Instrument: A zero-order instrument is one where the output follows the input perfectly and instantaneously without any time lag or distortion. The relationship is simply $y = Kx$, where $K$ is the static sensitivity.

2. The Potentiometer: A resistance potentiometer is a classic example of a zero-order system. As the wiper moves along the resistive element, the output voltage changes instantly in linear proportion to the displacement. It has no inherent energy storage elements (like mass, springs, or capacitors) that would cause a delay or oscillation in its basic ideal form.

3. Comparison with others:

• LVDT and Capacitive Transducers: These involve inductive or capacitive properties and often require signal conditioning that introduces first or second-order dynamics.

• Rota meter: This involves the movement of a float in a fluid, which is a second-order system due to mass, fluid damping, and buoyancy forces.