1、Absolute Pressure Transmitter
First of all, we all know that the absolute pressure transmitter is a kind of pressure transmitter. This is undoubted. According to the principle and name, it is natural to assume that the absolute pressure transmitter can measure the negative pressure (vacuum degree).
Absolute pressure transmitter is a pressure signal measured at the reference end of atmospheric pressure (or vacuum) with only one port connected to the process pipe.
So what is absolute pressure?
In simple terms, absolute pressure is a type of pressure that is measured and measured. The zero point of the starting pressure is absolute vacuum. It is equal to the sum of gauge pressure and atmospheric pressure. This is a conceptual distinction between the two
Structurally, the low pressure side diaphragm of the absolute pressure transmitter is vacuumed, while the low pressure side diaphragm of the pressure transmitter that measures the gauge pressure is in direct contact with the atmosphere. This is a structural distinction between the two.
Now I have extended from the conceptual point of view, the absolute scale of the absolute pressure transmitter and the pressure transmitter is not the same. The zero point of the ordinary pressure transmitter is the pressure in the atmosphere. The capsule is at standard atmospheric pressure, and the absolute pressure transmitter's zero point is the absolute vacuum. It seems to display the atmospheric pressure, but the corresponding zero point of 4mA shows the true value is zero, which is absolute pressure zero.
2、working principle of Absolute Pressure Transmitter
Its working principle is that when the silicon monocrystalline material is subjected to the action of external force to produce extremely small strain, the electronic energy level state of its internal atomic structure will change, resulting in the drastic change of its resistivity. This physical effect is called piezoresistive effect. Based on piezoresistive effect principle, an integrated process technology is adopted to make strain resistance along the characteristic crystal direction of monocrystalline silicon wafer after doping and diffusion, forming the Wheatstone bridge, and then a diffused silicon sensor integrating force sensitivity and force-electricity conversion detection is made.
When the pressure directly or indirectly ACTS on the surface of the silicon wafer and causes the diaphragm to produce tiny deformation, the high-precision circuit measuring the deformation of the silicon wafer transforms the tiny deformation into a voltage signal proportional to the pressure. After temperature and pressure compensation, this voltage signal is converted into industrial standard 4-20ma current signal or 1-5v voltage signal using a dedicated chip.
Since the measuring diaphragm detecting circuit uses an integrated circuit and contains a linear and temperature compensating circuit internally, high precision and high stability can be achieved, and it is convenient for use in various complicated industrial environments.