German HOFMANN sensors HOFMANN models HOFMANN prices

HOFMANN sensors are devices that convert magnetic signals into electrical signals. By utilizing the transformation relationship between magnetic quantities and other physical quantities, with the magnetic field as a medium, they can also convert signals of other non-electrical physical quantities into electrical signals. There are two driving methods: one is driven by a permanent magnet, and the other is driven by an electromagnetic coil. The former is mostly used for detection; for example, if a moving part is made of a magnet, it will attract and emit a signal once it approaches the magnetic induction sensor. The latter is mostly used for control; if the electromagnetic coil is energized, the contacts will attract. Using magnetic induction sensors to replace limit switches that rely on collision contact can improve system reliability and service life; therefore, they are often used in programmable logic controllers (PLCs) as signaling devices for position arrival.

HOFMANN sensor classification

Load cells are divided into 8 categories based on conversion methods, including photoelectric, hydraulic, electromagnetic force, capacitive, magnetic pole variation, vibratory, gyroscope, and resistance strain gauge types, with resistance strain gauge being the most widely used. 1) Photoelectric type: Includes grating and code disk types. Grating sensors use Moiré fringes formed by gratings to convert angular displacement into photoelectric signals. There are two gratings: one fixed grating and one moving grating mounted on the dial shaft. The measured object placed on the weighing platform rotates the dial shaft through the force transmission lever system, driving the moving grating to rotate and causing the Moiré fringes to move. By using a phototube, conversion circuit, and display instrument, the number of moved Moiré fringes can be calculated to measure the angle of grating rotation, thereby determining and reading the mass of the measured object. Code disk sensor: The code disk (symbol plate) is a piece of transparent glass mounted on the dial shaft, featuring black and white codes arranged according to a specific encoding method. When the measured object on the weighing platform rotates the dial shaft via the force transmission lever, the code disk also rotates by a certain angle. A photocell receives the light signal passing through the code disk and converts it into an electrical signal, which is then digitally processed by the circuit, finally displaying the number representing the measured mass on the display. Photoelectric sensors were mainly used in electromechanical combination scales. 2) Hydraulic type: When subjected to the gravity P of the measured object, the pressure of the hydraulic oil increases, and the degree of increase is proportional to P. By measuring the increased pressure value, the mass of the measured object can be determined. Hydraulic sensors have a simple and robust structure and a large measurement range, but the accuracy generally does not exceed 1/100. 3) Capacitive type: It operates based on the proportional relationship between the oscillation frequency f of the capacitor oscillator circuit and the distance d between the plates. There are two plates, one fixed and the other movable. When the measured object is loaded onto the weighing platform, the leaf spring deflects, changing the distance between the two plates, and thus changing the oscillation frequency of the circuit. By measuring the change in frequency, the mass of the measured object on the weighing platform can be calculated. Capacitive sensors consume little power, have low cost, and have an accuracy of 1/200 to 1/500.

HOFMANN sensor features

Resistors, inductors, and capacitors are the three major types of passive components in electronics. A capacitive sensor is a sensor that converts changes in the measured quantity into changes in capacitance; it is essentially a capacitor with variable parameters. Capacitive sensors have the following advantages: high impedance, low power, requiring only very low input energy. They can obtain large change amounts, resulting in high signal-to-noise ratio and system stability. Fast dynamic response, with operating frequencies reaching several megahertz. Non-b contact measurement; the measured object can be a conductor or semiconductor. Simple structure, strong adaptability, capable of working in harsh environments such as high/low temperatures and strong radiation, with wide application. With the development of electronic technology and computer technology, the disadvantages of capacitive sensors, such as susceptibility to interference and distributed capacitance, have been continuously overcome. Additionally, capacitive grid displacement sensors and integrated capacitive sensors have been developed. Therefore, they are widely used in non-electrical quantity measurement and automatic detection, capable of measuring parameters such as pressure, displacement, speed, acceleration, A degree, thickness, liquid level, humidity, vibration, and component content. Capacitive sensors have good development prospects.

HOFMANN sensor installation precautions

1) Handle load cells with care, especially small-capacity sensors using aluminum alloy as the elastic body. Any impact or drop caused by vibration is likely to cause significant output errors. 2) When designing the loading device and during installation, ensure that the axis of the loading force coincides with the force-bearing axis of the load cell to minimize the effects of inclined and eccentric loads. 3) Regarding level adjustment. If a load cell is used, its base mounting plane must be adjusted with a spirit level until horizontal. If multiple sensors are used for simultaneous measurement, their base mounting surfaces should be kept on the same horizontal plane as much as possible. The main purpose of this is to ensure that the force borne by each sensor is basically consistent. 4) Determine the rated load of the sensor used based on the load cell capacity selection specified in its instructions. 5) To prevent chemical corrosion, it is advisable to coat the outer surface of the load cell with Vaseline during installation. Avoid use in places with direct sunlight exposure and drastic environmental temperature changes. 6) Connect bypasses made of copper braided wire to both ends of the load cell loading device. 7) Do not extend the cable yourself. If extension is absolutely necessary, solder the joints and add moisture-proof sealant. 8) It is best to use baffles to cover the sensor around the load cell. The purpose of this is to prevent debris from falling into the moving parts of the sensor, affecting its measurement accuracy. 9) The sensor cable should be kept away from high-power power lines or places with pulse waves. If avoidance is impossible, the load cell cable should be threaded separately into an iron pipe, and the connection distance should be shortened as much as possible. 10) Determine the rated load of the sensor used based on the load cell capacity selection specified in its instructions. Although the load cell itself has a certain overload capacity, such situations should be avoided during installation and use. Sometimes short-term overload may cause permanent damage to the sensor. 11) For high-precision applications, the load cell and instrument should be used after preheating for 30 minutes.

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