High precision, easy to use, and durable. The Dewell 250-AF series inclined air filter pressure gauge is very simple and reliable. It has no moving parts—no mechanical linkages—so there’s no wear and tear, and it won’t get damaged by interference or vibration. No calibration is needed. The inclined mirror-like scale allows technicians to easily and accurately read tiny changes in differential pressure across filters without parallax error. You just need to occasionally zero it. If cleaning is needed, use soap and water.

Construction

The Dewell DURABLOCK® 250 AF series is made with tightly machined 1" thick solid acrylic that won’t break or warp during use. The indicator liquid’s drilled holes have an error of only ±0.0002", ensuring long-term high accuracy. A glass bubble level is installed inside the housing and sealed to prevent damage or interference. The scale is made of chrome-plated mirror brass, and the reading can be taken without visual error by adjusting the reflection on the curved surface. A safety valve is installed internally to prevent fluid loss due to pressure spikes. Red and green signals clearly indicate whether the filter needs cleaning. The pressure gauge is best used in ambient temperatures from -20 to 150°F. Connection fittings are sealed with O-rings but are easy to remove for zeroing or refilling the indicator liquid. Comes with a complete instruction manual.

▲ The economical 451-AF and 452-AF are similar to the 250 series, except they don’t have built-in overpressure protection valves. Each gauge comes with two A-324 14" compression fittings, though they are not listed. The body is 5/8" thick acrylic, and the scale is an aluminum plate coated with mirror epoxy.

A differential pressure gauge made of fully transparent acrylic with precise machining, accuracy up to ±1% of full scale.  

Measures positive pressure, negative pressure, or differential pressure of gases; multiple ranges: from 0.1-0-1.0″wc to 0.2-0-3.0″wc / from 0-1.5″wc to 0-4″wc; accuracy: ±1% FS.