Level indicators utilize a mechanical device, such as a float, or a sensor with output signal to indicate the level within a tank. Level controllers are, essentially, indicators with
integrated control output which allows for functions such as on/off, alarms, etc.
Level Indicator Technology
Float
Float level instruments are mechanical devices that move in conjunction with the level of the liquid medium. The movement of the float indicates the level and can actuate a switch or create an
output signal. Float level instruments are an economical and practical solution.
Depth / Pressure
Pressure based level instruments use pressure sensors at the bottom of a tank to measure the force exerted per unit area. For level applications, that force is the weight of the medium to be
measured plus any pressure acting on the surface. By knowing the density of the medium and compensating for the effect of ambient pressure, the resulting value can be converted to a level
measurement. The output signal generated can be used to display the depth or to actuate control functions.
Ultrasonic
Ultrasonic level instruments use sound waves to determine the level of liquids, solids, and slurries. Consisting of two elements, a high efficiency transducer and an electronic transceiver,
these non-contact systems measure the time for an ultrasonic pulse and reflected echo make a complete round trip between the transducer and the sensed material level. Ultrasonic systems can
also measure open channel flow, volumetric output, and differential level.
While highly accurate, ultrasonic level instruments must compensate for temperature. Applications involving heavy dust, foam or surface turbulence are not advised as the ultrasonic pulse can
be absorbed or otherwise distorted affecting accuracy.
Conductive
Conductivity level indicators use a low-voltage, current-limited power source applied across separate electrodes to detect the medium's resistance when their electrodes are covered by the process
material. Normally used with water, wastewater, water-based liquids; conductive level probes are simple to install and use. They have the added benefit of being solid state.
Conductivity level indicators provide point level detection and are adept at switching functions for minimum, maximum or differential applications. If buildup insulates the probe from the medium,
it will stop working properly.
Points to consider when selecting level instruments:
- What is the material to be measured?
- Is the sensor to be placed inside or outside of the chamber?
- Do you need contact or non-contact measurement?
- What degree of accuracy is required?
- What are the pressure and temperature ranges needed?
- Is point monitoring or continuous measurement needed?
- What measurement range is needed?
- What type of output is needed?
- Is there any build-up of dust or foam to consider?
- What is the material of the tank?
If you have any questions regarding level instruments please don't hesitate to speak with one of our engineers by e-mailing us at sales@instrumart.com or calling 1-800-884-4967.
