A brief description of the method for measuring the level of strong acid and alkali with the magnetic flap level gauge and magnetostrictive meter

In the industrial field, on the level measurement of concentrated acid and concentrated alkali, the currently used measuring instruments include a contact-type anti-corrosion liquid level detection device, a magnetic flap level gauge, an ultrasonic liquid level detector, and the like. According to the investigation of the Yangcheng Power Plant in Shanxi Province by technicians, there are more than 20 acid-alkali tanks of different sizes in the production plant area. For the detection of the acid-alkali level in these tanks, ultrasonic level gauges and magnetic flap level gauges are mostly used. The combined approach. Specifically, the ultrasonic level gauge transmits the information of the acid-base level to the computer through the line for real-time observation.

However, in the ditch with the technicians at the production site, it has been learned that the use of an ultrasonic level gauge has a fatal disadvantage. The ultrasonic probe mounted on the top of the can is easily covered with acid mist or alkaline fog, which seriously affects the measurement accuracy and requires work. The personnel regularly cleaned the ultrasonic probe. The magnetic flap level gauge has no automatic data transmission function, requiring the staff to regularly observe the liquid level scale. In order to ensure the reliability of the acid-base level data, the plant technician proposed to add a set of liquid level detection device requirements, and can achieve automatic data transmission. To this end, the author uses a combination of a magnetostrictive sensor and a magnetic flap, based on the working principle of a magnetostrictive liquid level sensor and a magnetic flap liquid level detection device, to combine a magnetostrictive sensor and a magnetic flap level gauge. Through experiments, the magnetostrictive and magnetic flap devices share a magnetic float, and combined with MCU easing GSM technology to achieve a magnetostrictive-magnetic flap integrated liquid level detection device for strong acid, strong alkali and alkali liquid level Non-contact measurement. Realize the wireless transmission of magnetostrictive liquid level signals.

1 Measurement principle of magnetostrictive liquid level sensor and magnetic flap level gauge 1.1 Principle of magnetostrictive liquid level sensor Magnetostrictive linear liquid level sensor adopts non-magnetic stainless steel tube (rod), magnetostrictive Lines (waveguides), floats (containing magnetic rings) that can move with the liquid surface or interface, and electronic components (see Figure 1). The working principle is that the pulse generator generates current pulses that can be converted by electronic components. A waveguide pulse (starting pulse) that propagates along a waveguide (Waveguide); its magnetic field is added to the magnetic field of the magnetic ring in the float to form a spiral magnetic field, which produces an instantaneous torque that twists the waveguide and generates a stress pulse (Strainpulse) . This pulse is transmitted back along the waveguide at a fixed speed, and a sensed current pulse (termination pulse) is generated across the inductive coil of the electronic component. By measuring the time period between the start and end pulses and multiplying this fixed speed, the displacement or level of the measured object can be accurately determined. The entire measurement process is continuous, so whenever the float (magnet) is moved, the new position will be sensed quickly.

1.2 The working principle of the magnetic flip liquid level sensor The magnetic flip liquid level gauge is a buoyancy type liquid level gauge, the float is magnetic, the float rises or falls with the change of the liquid level, see Fig. 2. The flipper mounted next to the float is made of thin magnetically conductive metal sheets (some are cylindrical), painted on both sides in different colors. When the magnetic float raises and lowers, the flap is rotated around the shaft, the flap above the float is a color (such as white), the flap below the float is another color (such as red), and the liquid level can be known by observing the outside color. High-low magnetostrictive sensor and magnetic float level gauge principle Figure 2 Design of magnetostrictive-magnetic integrated integrated flap level measuring device 2.1 Magnetostrictive-magnetic flap common magnetic float experiment To avoid magnetostrictive liquid level The contact between the sensor and the strong acid and alkali, we combined the magnetostrictive sensor with the magnetic flap level gauge, and adopted the design idea that the magnetic flap level gauge and the magnetostrictive sensor share a magnetic float. We measured the magnetic field on the magnetic float in the magnetic flap and the magnetic loop on the magnetostrictive rod. The magnetic float in the magnetic flip level gauge uses a horizontally placed ferrite magnet disc. The magnetic field is shown in Fig. 3. The strongest magnetic field is in the center of the wafer, about 150 T. The magnetic field around the disc is tight. With an intensity of about 80T, the magnetic field decreases in the radial direction. The magnetostrictive sensor is generally provided with a floating ferrite ring as a magnetic float on the sensor bar. The magnetic field is shown in Figure 4, and the magnetic field at the center of the magnetic ring is the strongest, about 60T.

In order to remove the magnetic ring on the magnetostrictive rod, the magnetic field around the magnetic floater of the magnetic flap is used to replace the magnetic field of the magnetic ring; that is, the magnetostrictive rod is erected vertically beside the magnetic flap to form a magnetostrictive-magnetic flap An integrated liquid level measuring device is shown in Fig. 5 for its experimental device. When the liquid level in the liquid pipe of the magnetic flap changes, the magnetic float floats up and down, the small cylinder-shaped magnetic stick of the magnetic flip liquid level gauge flips, the color changes, and the liquid level in the tank can be observed by using a scale on the side. Variety. At the same time, the magnetostrictive rod also generates a pulse signal due to the floating of the magnetic float and the induction is a change of the displacement, thereby detecting the change of the liquid level in the tube.

2.2 magnetostrictive - magnetic flap level meter combination detection device strong acid and alkali tank level detection system shown in Figure 6, due to the old magnetic level gauges do not have automatic data recording and storage functions, we put the magnetic The telescopic rod can be installed at the position next to the magnetic flap for level measurement. The standard liquid level signal generated by magnetostriction is measured and stored by a single chip microcomputer. And set to real-time measurement mode, the measurement frequency can be set according to the needs of the site once per minute. In order to achieve the staff's understanding of the liquid level situation at any time and reduce the wiring, the system adopts the data wireless transmission method based on MCU and GSM (mobile short message transmission) [4]. When working, the staff’s mobile phone number is set as the GSM short message transmission number. The staff only needs to send a recall command to GSM, and GSM can send the liquid level data to the staff’s mobile phone in the form of a short message.

Magnetostrictive - magnetic flap combination detection device strong acid and alkali tank level detection system Figure 3 experiments and conclusions We integrated the detection device shown in Figure 5 for the water level test experiment, the test results and the actual water level value in the table 1.

The detection accuracy of the integrated detection device The actual water level value in Table 1 is the measurement value of the ruler with an accuracy of 1 mm. The magnetostrictive sensor measurement value is the value read by the SCM measurement and control device. The measurement value of the magnetic flap level gauge is passed. The value shown on the liquid column was read manually. It can be seen that the reading accuracy of the liquid level of the magnetostrictive sensor is 1%, and the accuracy is high; the measurement accuracy of the magnetic flap is 1cm, but the measurement result is consistent with the actual value. We controlled the magnetostrictive sensor's measured value by wireless remote transmission through the single-chip microcomputer, realizing the real-time monitoring of the liquid level of the acid-alkali tank. Therefore, the magnetostrictive-magnetic flap level gauge integrated combination device is feasible for the detection of the level of the acid-alkali tank. (This article was published by Runzhong Instrument Technology Co., Ltd.)

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