Mid-West Instrument”s Model 121 indicating differential-pressure switch is a heavy–duty version of the Model 120, featuring the same rugged, field-proven piston/housing design. In addition, the switch has a heavy-duty, industrial-type terminal strip for either one or two switches. Wiring can be performed with 1/2” NPT conduit interface and a removable cover. A variety of switching configurations is available with one or two hermetically sealed switches in SPST, SPDT configuration with 240 V, three W, or 60 W ratings. The switch is available in aluminum or 316 SS pressure housing with 316 SS and ceramic internal parts. Safe working pressure is 6,000 PSIG (zero to 400 bar). Differential pressure ranges from zero to five PSID (zero to .3 bar) to zero to 110 PSID (zero to 7 bar) with +/- 2 percent accuracy. The weather-resistant gauge front is of reinforced engineered plastic for corrosion resistance.