Question

A $3\frac{1}{2}$ digit multi meter has an accuracy specification of 0.5% of reading plus 5 counts. The value of an unknown resistance is read as $50.0\Omega$ on the $200\Omega$ scale of the meter, the value of the resistance is

• A. $50.0\pm 0.25\Omega$
• B. $50.0\pm 0.5\Omega$
• C. $50.0\pm 0.75\Omega$
• D. $50.0\pm 100\Omega$

Answer 1

The correct option is C $50.0\pm 0.75\Omega$

$50\Omega \text{will be displayed as;}$ $050.0$ $\Omega$

$error=\pm \left(0.5\%\text{of reading + 5 counts}\right)$

number of counts from 0 to 1999 are 2000

$\therefore \text{error}=\pm [(5\times \frac{0.5}{100})+50\times \frac{200}{2000}]\Omega$

$=\pm 0.75\Omega$