The SDB500 is a Direct Mounting Temperature Swichgage instrument used to monitor gas compressor temperatures or engine exhaust temperatures. It is an accurate direct-reading gauge with an adjustable limit switch to activate alarms and/or shutdown. A knob on the front of the instrument allows you to adjust the limit switch trip point. Pointer movement is actuated by a bi-metallic sensing element.

When the indicating pointer on the SDB500 touches the adjustable contact, a one-wire-to-ground circuit is completed to shut down the equipment and/or actuate audible or visible alarms. Proper relays or Tattletale annunciators (magnetic switches) must be incorporated into the system.

The SDB500 has a sand-cast aluminum case with a high-torque bi-metal sensing element in heliarc welded stainless steel bulb. This dual-scale instrument has a temperature range of 100-500°F (40-260°C), with a maximum unit temperature of 625°F (329°C). Use of a thermowell is recommended.

Murphy offers thermowells (separable sockets) to facilitate maintenance of a temperature Swichgage and to protect the temperature sensing bulb from extreme amounts of system pressure. Two thermowell options are available: 1/2 NPT and 3/4 NPT.