What is a Level Transmitter?


Your next project is well underway and you have decided that you need a level detector to measure level in a closed system. You know what a level detector can do, but with so many options on the market, you aren’t sure what your best option may be. Luckily, we are here to help.

A level transmitter is a physical device that translates fluid, gas, or bulk material level within a closed system into an electronic signal. This signal can then be used by a PLC (Programmable Logic Controller), uC (Micro-Controller), or a computer to routinely measure and control material levels within your next project. Although electronics may not be your forte, level transmitters are easy to use and provide an excellent way to automate your process.

There are numerous level detection devices on the market, such as level switches and level transmitters explains Semrad, however, many of them do not offer the same benefits as a continuous, Ultrasonic level detector. Why? Let’s find out.

Ultrasonic Level Detectors

Ultrasonic level detectors are non-invasive measurement device that operates on the principle of signal reflection. In other words, the device emits a signal of a particular frequency, often in the higher RF band, so that outsides sounds and impacts will not interfere with the measurement.

The signal emitted from the level detector travels within the enclosed system and bounces off the material that you are measuring. From this point, the signal will return upwards to register with the level detector. A simple, mathematical calculation utilizing the time difference between transmission and retrieval of the signal is performed to determine the level.

This process continues for as long as the level detector is given power, unlike many other level detectors that can only determine a high and low point.

Important Factors to Consider When Choosing an Ultrasonic Level Detector

Power Supply Requirements

All Ultrasonic Level Detectors require the use of an external power supply to function. For most ultrasonic detectors, a 12-36V power supply will be required. The voltage powering the device plays a vital role in determining the range of measurement that you get from the device.

In other words, if you need to measure a liquid at a distance of 5 meters from the level detector it will require less voltage than a liquid at 15 meters. However, applying the maximum voltage will allow the device’s maximum range to be achieved, even if you don’t need the entire distance measurement capabilities.

Level Detector Output Signal

All measurement devices, whether it be a level, humidity, or even acceleration detector, output one of two signals – Analog or Digital. Analog signals are the continuous type while Digital signals are quantized – their value will either be a 1 or a 0. Computers can only work with digital signals, so the problem of output signals is one that you need to consider before purchasing a level detector.

Ultrasonic level detectors that output a digital signal will work directly with your computing machine, i.e. ‘Plug-N-Play’. Analog output signals are a bit trickier and require the use of an Analog-to-Digital (A/D) converter. These converters do what their name implies – it converts the analog signal into a stream of bits (1’s or 0’s) that can be accepted by your computer.

Maximum Range Capabilities

The maximum range of a level detecting device is limited by manufacturing processes and material composition. Every device will have different range capabilities that entail different applications.

Not only do material selection and manufacturing processes play a crucial range in its range, but the voltage powering the detection device does as well. Ultrasonic level detectors generate a high-frequency signal to measure material levels, and these signals require power to be transmitted. A higher voltage given to the level detector will result in higher range capabilities.

Device Output Impedance

Output Impedance is a term used by Electrical Engineers and hobbyists alike to describe a device’s ability to oppose and conduct current. In layman’s terms, it is the resistance of an electronic device when said device is operating with Alternating-Current signals.

The output impedance is important to level detection devices because they output a low-current signal. From the laws of nature, resistance multiplied by current will give the resultant voltage – which is what your computer relies on for signal acquisition. If the output impedance is not an optimal value, the resultant voltage will either be too high or too low.

Output Impedance of your ultrasonic level detector plays a crucial role in the accuracy of your data. There are numerous resources and calculators out there that will assist you in selecting an optimal output impedance so that your device can perform accurately.

Wrapping Up…

Level transmitters are an indispensable tool for level acquisition for all of your automation needs. They are simple electronic devices that can plug directly into your computer to begin measuring material levels. Although there are many devices capable of performing level detection, the Ultrasonic Level Detector offers the best features in terms of ease of use, accuracy, and durability, all the while remaining non-invasive to the material you need to measure. 

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