Question

The temperature of a furnace is increasing at a rate of 1°C/min. If the temperature of the furnace is masured using first order instrument with a maximum error of 0.5°C . Then the maximum permissible time constant of this first order instrument is ___________ sec.

• A. 30
• B. 60
• C. 45
• D. 15

Answer 1

The correct option is A 30

$\therefore$ Temperature of furnace is increasing in a ramp manner
$\therefore$ maximum steady state error for a ramp signal applied to a first order ins
trument is given by

$e_{ss}=K_{\tau }$

maximum allowable time constant

$\tau =\frac{e_{ss}}{K}=\frac{{0.5}^{o}C}{1^{o}C/min}$

$=0.5min=30sec$