JPS63101712A - Electronic type differential flowmeter - Google Patents

Abstract

PURPOSE:To check any displacement from appearing in a differential output, by a method wherein pressures on high and low pressure sides are detected with respective pressure sensors and electrical differences therebetween are differentially amplified to determine the root of an output so that variations in the pressure in a piping, changes in the outside air temperature and changes due to hysteresis are cancelled therebetween. CONSTITUTION:As a fluid passes through a piping passage 1, a differential pressure is generated on both sides of an orifice 2. The pressure is introduced to lead paths 3a and 3b and drawn electrically with pressure sensors 4a and 4b to be fed to a control means 5, with which pressure sensor outputs on high and low pressure sides are inputted into amplifiers 6a and 6b and outputs thereof are processed with a differential amplifier 7 and a root circuit 8 to output. Thereafter, the resulting outputs are sent to a receiving display device or an electric transmission section as required. When a temperature drift occurs, an output as differential pressure P1-P2 is almost constant as drift rate of the respective pressure sensors on the high and low pressure sides are approximate to each other, thereby minimizing influence of temperature regardless of any drift.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electronic differential pressure flowmeter.

[Prior art] In a flow meter that generates and measures differential pressure, the flow rate Q is 1
It is expressed by the formula.

In equation (1), Pl is the high pressure side pressure, P2 is the low pressure side pressure, and the flow ff1Q is proportional to f--P2-.

The differential pressure PI-P2 can be measured with a manometer using a mercury column or a water column. However, it is inconvenient to use a mercury column or a water column manometer when transmitting on-site instructions, such as Airoha and Electrical Transmission, and various methods are currently used to detect differential pressure.

[Problems to be Solved by the Invention] Conventional differential pressure flowmeters are equipped with a differential pressure converter that converts the differential pressure into another physical layer and displays it. For example, there are various methods such as mechanical operation method, reactance method, inductance method, strain gauge method, etc., but they are structurally complex. or,
Even with the strain gauge method, metal diaphragms are installed on the front and back of the strain gauge in the pressure receiving part between high and low pressures.
As expected, it became complicated, and the output was directly influenced by pressure fluctuations, temperature changes, and hysteresis due to strain gauges and attached structures, and it was not possible to accurately measure the output depending on the amount of correction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a differential pressure flow meter that has a simple structure and can perform accurate measurements.

[Means for Solving the Problems] In order to achieve the above object, the present invention detects the pressures P+ and P2 on the high and low pressure sides with pressure sensors and electrically Before or after amplification, the electrical difference between Pl and P2 is differentially amplified, and the output is passed through a square root circuit to display a flow boat or to transmit electricity.

[Example 1] Figure 1 shows a cross-sectional view of the electronic differential pressure flowmeter of the present invention, where 1 is a piping flow path, 2 is an orifice, 3a13b is a pressure guide path on the high and low pressure side, 4a and 4b are pressure sensors, 5 is a control means.

When fluid passes through the piping channel 1, a pressure difference is generated on both sides of the orifice 2. This pressure is guided to pressure guiding paths 3a, 3b, electrically extracted at 4° by pressure sensors 4a, 4b, and sent to control means 5. The control means 5 inputs the high and low side pressure sensor outputs to amplifiers 6a and 6b, respectively, as shown in the block diagram of FIG.
The square root circuit 8 processes and outputs the signal, and thereafter sends it to a receiving display device or an electrical transmitter as required.

FIG. 3 is an output diagram when the pressure inside the pipe changes in the flowmeter. Differential pressure P+-P2 even if the pressure changes
is constant.

Moreover, FIG. 4 is an output diagram when the outside air temperature changes.

When a temperature drift occurs, the output of the differential pressure PI-P2 is almost constant because the drift rates of the pressure sensors on the high pressure side and the low pressure side are similar. In other words, even if there is drift, the influence of humidity is small.

[Effects of the Invention] According to the present invention, changes due to pressure fluctuations in piping, outside temperature changes, and hysteresis occur in the same way as the sensor outputs of high and low pressure side pressures P1 and P2, so they are canceled out and the displacement becomes a differential output. It is difficult to express.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the electronic differential pressure flowmeter of the present invention, Figure 2 is a block diagram of detected output, Figure 3 is an output diagram when the pressure changes, and Figure 4 is when the outside air temperature changes. It is an output diagram at the time. 1... Piping channel, 2... Orifice, 3a, 3b.
...Pressure path, 4a, 4b...Pressure sensor, 5...Control means.

Claims (1)

[Claims] A pressure sensor is installed to electrically detect the pressure on the high-pressure side and low-pressure side in the area where differential pressure is generated in the piping flow path, and the difference in the output of the pressure sensor is converted into flow rate, and control is performed to display or send electricity. An electronic differential pressure flowmeter characterized by being provided with means.