Some issues with seismic pressure gauges?
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1. Why does the pressure gauge become inaccurate sometimes if the plug on it isn’t loosened? 2. Are there any requirements regarding the oil level of seismic pressure gauges?
There will be pressure inside the gauge due to thermal expansion and contraction; the Panasonic plug ensures that the gauge is in contact with the atmosphere, and 2/3 or 3/4 of the oil level is sufficient under normal conditions
There may be residual air pressure, so it needs to be vented to reset. The normal oil level at the time of leaving the factory is around three-quarters full, or about 75%. There are two types of oils that can be used: one is glycerin, which serves primarily to provide shock resistance; the other is silicone oil, which also provides shock resistance. However, silicone oil can withstand lower temperatures better than glycerin – at -20°C outside, glycerin will crystallize, while silicone oil still allows the instruments to function properly.