(7) With suitable connections made and the manometer adjusted, apply
pressure (or vacuum) to the manometer and the instrument being tested.
Gradually apply pressure, covering the entire instrument range, and
record comparative readings.
Should varying manometer readings be
obtained as you increase or decrease pressure, it may indicate a soiled
glass tube. CAUTION: The range of the instrument being tested--not the
manometer--determines the maximum pressure or vacuum that should be
(8) Depending on the liquid used, the meniscus may be concave or convex.
Always read the liquid level in the center of the tube (tangent to
meniscus surface) regardless of the form the liquid takes.
manometer scales are graduated for observed readings at 20 C. (68 F.)
If measurements are made at a temperature other than 20 C. (68 F), the
readings must be multiplied by a temperature correction factor.