UNOG (use no oil) gauges feature pressure scales with 2.5% full scale accuracy. They are available in 2 and 2 1 /2 in. sizes with polished brass housings and copper alloy wetted parts. They withstand ambient temperatures of -4° to 140° and maximum pressures from 30 to 4000 psi. A 1 /4 in. male NPT bottom connection is standard for indicating pressure of non-corrosive gases (as in accumulators), which would otherwise oxidize with oil-based compounds.
Dwyer Instruments Inc., (800) 872-9141, www.dwyer-inst.com