At present, users have been feeding back some quality problems about SF6 gas density meter and density relay, here is a summary of some of the problems, and analysis and answers. The details are as follows.
First of all, the user's feedback of this situation is normal, because the product is not ordinary pressure gauge, which will change with the temperature and the pointer indication changes differently because of temperature compensation. When the ambient temperature is greater than 20 ℃, the pointer will be low; when the ambient temperature is less than 20 ℃, the pointer will be high. How much deviation depends on the rated pressure of the meter: deviation value = rated pressure at the current temperature of the pressure minus rated pressure.
Most of the SF6 gas density meter and SF6 relay on the market are using bi-metal for temperature compensation principle. The bi-metal is set inside the case, sensing the ambient temperature, and bi-metal belongs to stamping processing parts, there is processing error, then there will also be a time error in temperature sensing, but the final compensation accuracy can meet the requirements. Therefore, it is because of the different sensing time of the bi-metal to the change of ambient temperature, which leads to the inconsistent reading of the density meter under the non-inflated state.
Because SF6 gas density meter and SF6 density relay are precision instruments, which are vulnerable to vibration and shock, in the transport links there will be quality problems for some meters. Users should know how to quickly determine whether the meter is good or bad, which is crucial. It is recommended that customers can refer to the factory inspection design of the product: the factory inspection of the product not only ensures the accuracy of each meter, but also ensures the consistency of the same batch of products. Twelve to twenty products can be installed on the same gas circuit at the same time, so that the accuracy of each meter can be ensured and the consistency inspection of the same batch of products can be achieved. In accordance with the relevant testing standards, the meter should be installed vertically when testing, where the concept of vertical installation is: the dial is facing the user, because if the meter is installed diagonally, or vertically, the reading will have errors.
Because the contact structure of most of the SF6 relays on the market is magnetic-assisted electric contact, and the contact is opened by pointer toggle, and is closed by magnetic adsorption, if the inflation pressure and contact value is very close, after tapping the case, there will be sucked contact, and then tap the case, contact is disconnected. So from the surface, we can see the pointer change is very large.