Gas-Actuated Thermometer

The gas-actuated thermometer is the choice when a bimetal thermometer cannot reach: the range is too high or too low, the reading is needed some distance from the measuring point, or the dial has to sit on a panel. Bulb, capillary and Bourdon-type measuring element form a sealed system filled with inert gas; the gas pressure follows the bulb temperature and moves the pointer through the movement. The response is fast and linear, and the system is unaffected by vibration and ambient temperature changes along the capillary.

Ranges span −200 to +700 °C, from cryogenic service to exhaust and furnace duty, with class 1 accuracy to EN 13190 and the tolerance depending on the selected range. The 316 stainless steel bulb mounts through a ½" or ¾" thread, a union nut or a compression fitting, directly with an adjustable stem and dial, or remotely on a capillary of up to 60 m. Surface-contact bulbs measure pipe and vessel walls. Accessories include mounting brackets and panel flanges.

Applications are remote indication on tanks, pipelines, machinery and control panels, and any harsh or high-vibration environment where a direct-mounted instrument would suffer. Users are chemical, petrochemical, oil and gas, power, water and wastewater, food and beverage and general industry.