Question

Design a U-tube manometer that can measure gage pressures up to 69 kPa of air. You will want to choose a manometer fluid with good static sensitivity but will not result in an unreasonably tall manometer. Further, the manometer fluid should be mostly immiscible with the air. The two design parameters you should consider are manometer fluid (impacts manometer fluid density) as well as the manometer height.
Required:
Compute the static sensitivity, K, in mmHg/Pa

Answer 1

Answer:

The answer "K = 0.0075"

Explanation:

If we try to measure up to 69 kPa of air, find mercury or fluid for gauge.  

While mercury was its largest liquid with a density of 13600 kg / m3 at normal room temperature.  

Let's all measure for 69 kPa that height of the  mercury liquid column.

$\to P = 69 \ kPa$

       $= 69000 Pa$

$\to \rho = 13600 \ \ \frac{kg}{m^3} \\\\\\to g = 9.81 \ \ \frac{m}{s^2}$

Formula:

$\to P=\rho \ gh$

$\to 69000 = 13600\times9.81 \times h\\\\\to h= \frac{69000}{13600\times9.81} \\\\\to h= \frac{69000}{133416} \\\\\to h= 0.517179349 \\\\ \to h= 517 \ mm$

The right choice for pressure measurements up to 69 kPa is mercury.  

Atmospheric Mercury up to 69 kPa Air 517 mm  

The relationship of Hg to Pa is = 134.22 Pa 1 mm Hg  

Static sensitivity to Pa of mm hg = change of mercury height to Pa:

$= \frac{\Delta Hg }{ \Delta P }\\\\= \frac{1 }{ 133.3 }\\\\= 0.0075$