Some pressure gauges contains oil, but some do not. Is there any difference between them? The difference is there, but it is not a big difference, just the difference between the two application occasions. So what does the "oil" in the pressure gauge function as?
In fact, the resistance of oil filled pressure gauge increases after oil filling, so the pointer is relatively stable, which can prevent the needle from shaking. It is also the shock-resistant pressure gauge we often say. It is generally used in harsh environments (such as a noisy environment), or used in large pressure fluctuations in the system (such as a plunger pump) to make the pressure gauge reading accurate and prolong the service life.
Can this "oil" be chosen at will? The answer is definitely NO! This "oil" is mainly glycerin and silicone oil. The effects of the two oils are not the same. Glycerin mainly plays a role in shock resistance; silicone oil can also play a role in shock resistance, but silicone oil is more resistant to low temperatures than glycerin. If the outdoor temperature reaches minus 20°C, glycerin will crystallize. But silicone oil can also make the meter work properly.
Therefore, both glycerin and silicone oil can be used, but at least two points should be considered when making specific choices:
1. For the thermal expansion coefficient, the smaller the coefficient, the better, and this is mainly affected by temperature;
2. For the application field, neither of these two oils can be used in the food industry. In case the diaphragm is damaged, the oil will contaminate the food. It is also not recommended to measure strong oxidants, otherwise it will cause an explosion.