Explain level sensor based on immersed resistor ?
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Level Sensors Information
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Level sensors are used to detect liquid or powder levels, or interfaces between liquids. They are an important part of a fluid system because the position and displacement of an object or media is critical to know in many applications. The substance to be measured could be inside a container or in its natural form such as a lake or river. A sensor is able to detect a change and communicate that change with a user. Level sensors are generally designed for a specific application, rather than general application.
There are two basic level-measurement types, point level and continuous level sensors. Below is a video which explains each measurement.
Point level sensors or multi-point sensors mark a specific level and communicate to the user if the media is above or below that level. They are used generally as a high alarm or switch. These level sensors can also be integrated in a single device to add a low alarm, or to serve as a stepped version of a continuous level.
Continuous level sensors measure liquid or dry material levels within a specified range and provide outputs which continuously indicate the level. They are more sophisticated devices than point level sensors because they measure over a range of levels instead of at one point to let the user know the exact amount of a substance. This produces an analog output that directly correlates to the fluid level in the container.
Level Sensor Devices
There are three major device classifications for level sensors:
Sensor-only devices provide outputs for processors, controllers, or data acquisition systems; however, they do not have a display or user interface. Typically, sensor-only devices are used in applications that require a switch.
Level sensor systems are simple instruments or gauges. These level sensors provide more capabilities than sensor-only (transducer) devices, and may include a display and/or user interface. Generally, level sensor systems are designed for applications that require a simple gauge, a locally-programmable (stand-alone) unit, or a controller/totalizer.
Sensor transmitters are designed to transmit data from the sensor via a two-wire current loop. The loop has an external power supply, and the transmitter acts as a variable resistor with respect to its input signal.
Product Selection
There are several important specifications to consider when selecting a level sensor. These include: the media you will be measuring, contact or non-contact measurement, type of level measurement technology, temperature and pressure ranges of the system, and output needs.
Contact or Non-contact
Level sensors measure using contact or non-contact methods. Contact methods involve physical contact between the device and the media, while non-contact methods measure without touching the media. Non-contact methods are the best choice for servicing corrosive media.
Media
Media is the material that the sensor needs to measure. Level sensors can be responsible for measuring a wide variety of media in fluid level systems in many industries. The two general media types include liquid and dry materials.