List of top Instrumentation and Process Control Questions on Measurement of process variables asked in GATE CH

Consider the surge drum in the figure. Initially, the system is at steady state with a hold-up \( V = 5 \) m³, which is 50% of the full tank capacity, \( V_{\text{full}} \), and volumetric flow rates \( \vec{F}_{\text{in}} = \vec{F}_{\text{out}} = 1 \) m³/h. The high hold-up alarm limit \( V_{\text{high}} = 0.8 V_{\text{full}} \) while the low hold-up alarm limit \( V_{\text{low}} = 0.2 V_{\text{full}} \). A proportional (P-only) controller manipulates the outflow to regulate the hold-up \( V \) as \( \vec{F}_{\text{out}} = K_c (V - \vec{V}) + \vec{F}_{\text{out}} \). At \( t = 0 \), \( \vec{F}_{\text{in}} \) increases as a step from 1 m³/h to 2 m³/h. Assume linear control valves and instantaneous valve dynamics. Let \( K_c^{\text{min}} \) be the minimum controller gain that ensures \( V \) never exceeds \( V_{\text{high}} \). The value of \( K_c^{\text{min}} \), in h\(^{-1}\), rounded off to 2 decimal places, is _____.

A PD controller with transfer function \( G_c \) is used to stabilize an open-loop unstable process with transfer function \( G_p \), where \( G_c = K_c \frac{(T_D s + 1)}{(\frac{T_D}{20})s + 1} \) and \( G_p = \frac{1}{(s - 1)(10s + 1)} \), and time is in minutes. From the necessary conditions for closed-loop stability, the maximum feasible value of \( T_D \), in minutes, rounded off to 1 decimal place, is _____.

Consider the block diagram in the figure with control input u, disturbance d and output y. For the feedforward controller, the ordered pair (K, a/ẞ) is

Which of the following is NOT a standard to transmit measurement and control signals?