Comparison of on-site thermometers
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1. What are the differences between bimetallic thermometers and pressure-type thermometers, and what is the difference in accuracy? Capillary length limitation? What are their respective advantages and disadvantages? 2. Some thermometers with capillaries require batteries, while others do not; is there any difference between them? Can those with batteries meet the explosion-proof requirements?
In situations where there is vibration in the process pipelines and equipment, the medium is at low temperatures, the operating environment is hot, or remote indication is required, pressure-type thermometers equipped with capillaries are advisable. The temperature measurement range should be from -200°C to 700°C, and the accuracy across the full scale should not be lower than ±1.5%. The length of the capillary should not exceed 10m, it should have a shielding layer, and the material of the capillary should be stainless steel.
Bimetallic thermometers rely on the properties of bimetallic strips; they do not have a capillary. The bending of these bimetallic strips is used to directly or indirectly drive the pointer to move, with all connections being of the hard-tail type – no capillaries are involved. The manufacturing process is much easier than the pressure type.
Thermometers with capillaries are usually pressure-type and have a pointer for indication. No battery is required. Thermistor with battery, digital display thermometer. The explosion-proof requirements can be met whether a battery is used or not.