All those aneroid YJ-type don't hold calibration. Even a Dwyer Magnahelic can get to the point it won't calibrate and it has a screw adj. The UEI is rugged and cheap and it works well right up until its death.
I find the manometer in my combustion analyzer unreliable (Bach. FRP125)
I always have a water manometer for incident investigations since they are lab accurate and I check my digitals against it periodically on both the high and low end.
For depressurization testing, I use a Energy Conservatory digital micromanometer that reads in tenths of one Pascal with time averaging and get it calibrated annually.
For draft testing, I put my old Backarach black box on the shelf and use the Dwyer 460, which is cheap, light, compact and accurate.
I use Dwyer tips for static pressure and a telescoping pitot tube. For testing pressure switches I have a variety of barbed hose fittings and adapters.
Measurement of Pressure with the Manometer
Pressure is defined as a force per unit area - and the most accurate way to measure low air pressure is to balance a column of liquid of known weight against it and measure the height of the liquid column so balanced. The units of measure commonly used are inches of mercury (in. Hg), using mercury as the fluid and inches of water (in. w.c.), using water or oil as the fluid.
Fig. 2-1. In its simplest form the manometer is a U-tube about half filled with liquid. With both ends of the tube open, the liquid is at the same height in each leg.