The difference between oil filled and non oil filled bimetallic thermometers is mainly the difference between their use occasions。The oil bimetal thermometer is mainly used in the place of environmental vibration, while the non oil filled bimetal thermometer, i.e. ordinary bimetal thermometer, is mainly used in the ordinary place.
The main purpose of oil filling of bimetal thermometer is to reduce the interference of external vibration environment on the pointer and to ensure the sensitivity of thermometer.Is this "oil" optional? The answer is No. This "oil" is mainly glycerin and silicone oil. The functions of the two kinds of oil are also different. Glycerin mainly plays an anti-seismic role; silicone oil can also play an anti-seismic role, but silicone oil is more resistant to low temperature than glycerin. If the outdoor temperature reaches - 20C, glycerin will crystallize, but silicone oil can make the instrument work normally.
Both glycerin and silicone oil can be used,but at least two points should be taken into account when making specific choices: 1、The coefficient of thermal expansion, the smaller the coefficient, the better, which is mainly affected by the temperature; 2、Occasion of useing. Neither oil can be used in the food industry. In case of diaphragm damage, the oil will pollute the food. It is also not recommended to use the place where strong oxidant is measured, otherwise it will cause explosion.