German Murr sensors, Murr models, Murr prices

Murr pressure sensors for liquid level measurement. Submersible static pressure level transmitters (level gauges) operate on the principle that the static pressure of the measured liquid is proportional to its height. They use advanced imported isolated diffused silicon sensitive elements or ceramic capacitive pressure sensitive sensors to convert static pressure into electrical signals. These signals undergo temperature compensation and linear correction to become standard electrical signals (typically 4 to 20mA/16VDC).

Murr sensor classification

Load cells are categorized by conversion method into 8 types, including photoelectric, hydraulic, electromagnetic force, capacitive, magnetic pole variation, vibratory, gyroscopic, and resistive strain gauge types, with resistive 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 object being weighed on the load-bearing platform rotates the dial shaft via a force transmission lever system, driving the moving grating to rotate and shift the Moiré fringes. Using a phototube, conversion circuit, and display instrument, the number of shifted Moiré fringes is calculated to determine the angle of grating rotation, thereby determining and reading the mass of the object. Code disk sensors: A 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 object on the load-bearing 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 digital value representing the measured mass on the display. Photoelectric sensors were previously mainly used in electromechanical combination scales. 2) Hydraulic type: Under the action of the gravitational force P of the measured object, the pressure of the hydraulic oil increases, with the increase proportional to P. Measuring the increased pressure value determines the mass of the object. Hydraulic sensors have a simple and robust structure and a large measuring range, but accuracy generally does not exceed 1/100. 3) Capacitive type: It operates based on the direct proportionality between the oscillation frequency f of the capacitor oscillator circuit and the distance d between the plates. There are two plates, one fixed and one movable. When the object is loaded onto the load-bearing platform, the leaf spring deflects, changing the distance between the two plates and consequently changing the oscillation frequency of the circuit. Measuring the frequency change allows calculation of the mass of the object on the load-bearing platform. Capacitive sensors consume little power, have low cost, and offer an accuracy of 1/200 to 1/501.

Murr sensor structural composition

1) Sensitive element: The component that directly senses the measured quantity (mass) and outputs another quantity with a definite relationship to the measured quantity. For example, the elastic body of a resistive strain gauge load cell converts the mass of the object into deformation; the elastic body of a capacitive load cell converts the measured mass into displacement. 2) Conversion element: Also known as the sensing element, it converts the output of the sensitive element into a signal suitable for measurement. For example, the resistive strain gauge (or strain foil) of a resistive strain gauge load cell converts the deformation of the elastic body into a change in resistance; the capacitor of a capacitive load cell converts the displacement of the elastic body into a change in capacitance. Sometimes certain components perform the functions of both sensitive and conversion elements. For example, the piezoelectric material in a voltage-type load cell outputs electrical charge while deforming under external load. 3) Measurement element: Converts the output of the conversion element into an electrical signal to facilitate further transmission, processing, display, recording, or control. Examples include the bridge circuit in resistive strain gauge load cells and the charge preamplifier in piezoelectric load cells. 4) Auxiliary power supply: Provides energy for the sensor's electrical signal output. Generally, load cells require an external power source to operate. Therefore, as a product, power supply requirements must be specified, although the power supply is not considered part of the load cell itself. Some sensors, such as magnetoelectric velocity sensors, do not require an auxiliary power supply to operate normally because they output significant energy. Thus, not all sensors require an auxiliary power supply.

Murr sensor installation precautions

1) Handle load cells with care, especially small-capacity sensors with aluminum alloy elastic bodies. 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 line of action of the loading force coincides with the force axis of the load cell to minimize the effects of inclined and eccentric loads. 3) Regarding level adjustment: If using a load cell, adjust the installation plane of its base with a spirit level until it is horizontal. If multiple sensors are used for simultaneous measurement, their base installation surfaces should be kept on the same horizontal plane as much as possible. This is primarily 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, apply Vaseline to the outer surface of the load cell during installation. Avoid direct sunlight and environments with drastic temperature changes. 6) Install bypasses made of copper braided wire at both ends of the load cell loading device. 7) Do not extend the cable yourself. If extension is absolutely necessary, solder the joints and apply moisture-proof sealant. 8) It is best to use baffles to cover the sensor around the load cell. This prevents debris from falling into the moving parts of the sensor, which could affect its measurement accuracy. 9) Keep the sensor cable away from high-power power lines or places with pulse waves. If avoidance is impossible, run the load cell cable separately through an iron pipe and shorten the connection distance 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 load cells have a certain overload capacity, avoid such situations during installation and use. Even short-term overloading may cause permanent damage to the sensor. 11) For high-precision applications, allow the load cell and instrument to warm up for 31 minutes before use.

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