Generally speaking, __Hydraulic Oil Flow flow meter____ __is mainly divided into thermal mass flowmeter, differential pressure mass flow meter and Coriolis mass flow meter. The working principle of different kinds of hydraulic flow meter is different. The working principle of hydraulic flow meter is based on King's law. The external heat source is used to heat the measured gas in the pipeline. The heat energy flows with the gas. The mass flow of the gas is calculated by measuring the heat change caused by the gas flow in the pipeline, that is, the temperature change before and after the gas passes through the pipeline. Another method is to calculate the mass flow rate of gas by measuring the relationship between the energy required for the gas temperature to rise to a certain point and the gas mass.

**How Does Hydraulic Oil Flow Meter Work**

The sensor in hydraulic flow meter is usually composed of two reference thermal resistors, one is the speed sensor, the other is the temperature sensor to measure the gas temperature change. When the two thermistors are placed in the gas to be measured in the pipeline, the velocity sensor is heated and the other temperature sensor is used to measure the temperature of the gas. With the increase of gas flow, the heat taken away will rise, and the temperature of the temperature sensor itself will drop.

The temperature change before and after the temperature sensor is in linear proportion to the mass flow of the gas passing through the pipeline, so the mass flow of the gas can be calculated from the working principle. Calculation formula: P / △ t = a + B (QM) k, where p is the consumed power, △ t is the temperature difference before and after the gas passes through the pipeline, a and B are the physical constants of the reaction gas properties, QM is the mass flow rate, and K is the exponential coefficient.

In addition, the working principle of hydraulic flow meter is divided into constant temperature difference measurement method and the constant power measurement method. The working principle of constant power measurement method of thermal mass flow meter: Contrary to the above, it is to calculate the mass flow by measuring the temperature difference before and after the gas passes through the pipeline while keeping the heating power unchanged.

The working principle of constant temperature difference measurement method of hydraulic flow meter: as the name suggests, it is to calculate the mass flow of gas by measuring the change of heating power while keeping the temperature difference unchanged. Compared with the constant power measurement method, this method has the advantages of fast response speed and good linearity, up to 100:1.

**Working principle of differential **hydraulic flow meter

The differential hydraulic flow meter adopts Roseville's law. By measuring the pressure difference before and after the gas passes through a certain section of pipeline, that is, the pressure loss, the volume flow of gas is calculated, and then converted to the mass flow under standard working conditions. Formula: Q= Δ P ×π× r4/(8 η 50) Where: q is the volume flow rate of gas, Δ P is the pressure difference, i.e. pressure loss, R is the pipe radius, l is the pipe length, η For the sake of gas viscosity, there is a premise for the hydraulic flow meter based on Poiseuille's law, that is, the gas to be measured must move in laminar flow. This is about the state of gas flow. The flow state of gas is divided into the turbulent flow and laminar flow. Turbulence: gas makes irregular motion, which is produced by the partial velocity perpendicular to the direction of the pipe. This kind of motion is called turbulence

The hydraulic flow meter based on laminar differential pressure type works by letting the gas pass through a laminar flow sheet. The gap between the laminar flow sheets is absolutely invisible to the naked eye, but the gas can pass through the laminar flow sheet and keep the laminar flow movement between the laminar flow sheets. Then, according to the above-mentioned working principle based on Pineville's law, as long as the pressure difference between the two ends of the laminar flow sheet is measured, The flow rate of the gas in this section can be calculated.

Compared with the hydraulic flow meter based on the principle of measuring temperature difference, the differential hydraulic flow meter for measuring pressure difference has higher accuracy. I heard that this kind of measurement method seems to have a patent. The working principle of the hydraulic flow meter.

Coriolis mass flow meter, also known as Coriolis force mass flowmeter, its working principle is to make the bending part of the lower end of two side-by-side U-tubes vibrate slightly, so as to drive the straight tube to vibrate, and the two tubes are separated or closed at the same time, that is, the vibration is synchronous. At this time, if there is gas flowing through, the pipeline will force the flowing gas or liquid to vibrate together. In order to resist this forced vibration, the gas or liquid will exert a reaction force on the pipeline in its flow direction, which is called Coriolis force.

Under the action of Coriolis force, the vibration of the two pipes is not synchronous, and there is a difference. The difference can be detected by the circuit, and the difference is proportional to the mass flow of the gas passing through the pipe. Coriolis mass flowmeter is a kind of mass flowmeter which can measure gas flow based on this working principle. Coriolis mass flowmeter directly measures the mass flow of gas, and the measurement accuracy is relatively high.