Water Level Sensors

In the case of coffee machines with a permanent water connection, the same sensor approach applies except for the fact that there is no indicator light, but a water-switching valve is added instead. Generally speaking, this approach works well for all such fluid level applications. 

---

The rising water level is checked by the water level sensor. This is a pressure sensor. The pressure of the air in the plastic tube rises as it is compressed by the rising water. The pressure sensor keeps the control unit informed as to the pressure reached and the control unit uses the information to decide when to close the water inlet valves. 

A low pressure UV lamp (11W, Amax = 253.7 mn) was positioned vertically inside the quartz glass cylinder in the middle of the photocatalytic zone. Air was supplied from a porous titanium plate directly below the membrane module. The purpose of the aeration was to provide dissolved oxygen for photoreaction, to fluidize the IIO2 particles and to create sufficient turbulence along the membrane surface. The reaction temperature was controlled by using cooling water. Permeate was withdrawn from the system with the help of a suction pump. A water level sensor was used to maintain a constant level of solution in the reactor. Additionally, the exterior wall of the reactor was covered with a reflecting aluminum foil to improve the efficiency of UV utilization. 

Goebel R., Krska R., Kellner R., Katzir A., Development of Protective Polymer-Coatings for Silver-Halide Fibers and Their Application as Threshold Level Sensors for Chlorinated Hydrocarbons in Sea-Water, Fresenius J. Anal. Chem. 1994 348 780-781. 

The use of pressure sensors for water level switches, or in a more sophisticated form also for foam content surveillance in washing machines and dryers. 

Modem washing machines work with this type of pressure sensors with analogue output In such machines the software can be used to set any desired water level. 

Commercial laundry dryers can not be easily vented to the outside in the same way that home laundry dryers are. Because of this fact, the moist air is passed through a condenser where the water will accumulate. If there is no direct water drain, the water is directed to a holding tank. The water level is monitored using a magnetic float. When the water rises to the full level, the reed sensor is activated and shuts down the dryer. Once the water is removed, the reed sensor is deactivated, enabling the dryer to operate. 

However, very economical measurement of acceleration is possible when the washing machine is equipped with a high-resolution analog pressure sensor with microprocessor control. These pressure sensors come as a separate part or are integrated directly on to the PCB of the washing machine control. They work as differential pressure sensors and measure the static pressure via a hose in the lower part of the suds container, thus measuring the water level in the suds container (Fig. 5.57). 

This component consists of a housing with two fittings for the hose connections to the pressure sensor and to the lower suds container. The inner volume of the component is divided by an elastic membrane with a weight in the middle. A bore in the weight allows for the exchange of air between the chambers. Measuring of the water level is not affected because the bore always allows for pressure compensation. 

In order to measure the acceleration, the membrane mass is increased by an additional mass. In this way it is possible for this sensor to detect both the water level and the acceleration of the suds container. 

To run it under automated conditions, the bioreactor was equipped with two temperature sensors, two pH electrodes, a water level detector, a manometer and a computer-controlled electric valve. Control of key parameters (pH, temperature, dilution rates) has allowed to define the culture conditions producing maximal amounts of molecular hydrogen. 

The sample probe s vertical stroke can be as long as 100 mm and this, with the in built hquid level sensor, allows a wide range of primary tubes and centrifuge tubes to be held on the trays. Sample racks are automatically transported in the front section of the analyser, which in turn simpHfies maintenance should the nozzle become blocked or if mechanical problems arise. The AUSOOO Series provides precise sample dispensing capabihty. Each of the two sample probes aspirates a volume sufficient for a maximum of four chemistries per sample and dispenses it into eight cuvettes on the twin reactor Hnes. The probes are constructed from water-resistant plastic which minimizes any dilution from wash solution or contamination. The built-in level sensor Hmits the immersion of the probe in the sample. The inside and outside of the probe as well as the level sensor are rinsed after each use to further prevent contamination. 

Sonic (up to 9,500 Hz) and ultrasonic (10-70 kHz) level sensors operate either by the absorption (attenuation) of acoustic energy as it travels from source to receiver, or by generating an ultrasonic pulse and measuring the time it takes for the echo to return. If the transmitter is mounted at the top of the tank, the pulse travels in the vapor space above the tank contents, and if it is mounted on the bottom, the time of travel reflects the depth of liquid in the tank. In water, at ambient temperature, the ultrasonic pulse travels at 1,505 m/s (4,936 ft/s). 

The auxiliary treated-oil tank (T-2A) holds 2840 L (18 bbl). The inlet, which can accept flow from the DPET and the HOE or the larger T-2 tank, is equipped with an in-line BS W meter to monitor the water content of the treated-oil-bitumen stream. If the water content is not sufficiently low, the product may be recycled back to the HOE treater. This tank also has a heater and a level sensor to act as a low-level alarm to turn off the heater. 

Basically the system is fed electrolyte or distilled water from a reservoir via a pump that can be manually and level sensor activated. The reservoir will supply water or electrolyte to the electrolyzer and a pressure tank with a sight glass. The sight glass on the pressure tank shows the fill level in the pressure tank and the electrolyzer, and when a predetermined level is reached, the pump is switched off, either manually or automatically with sensor switches. When the electrolyte reaches the fill level, the power to the electrolyzer is switched on manually or automatically, and the electrolyzer begins to disassociate hydrogen from oxygen in the electrolyte. 

When the water level is at the full position neither sensor activates. When the water/KOH level falls below the detection range of the normally closed sensor the pump is turned on and begins to fill the tank and electrolyzer. When the water/KOH line reaches the detection range of the normally open sensor the pump is turned off. This arrangement, as shown in the illustration on the previous page, works quite well. 

Hydrological monitoring is based on data collected from 1000 gauging stations in rivers, lakes and water reservoirs. Information on the water levels is supplied in 10 minute cycles. Water level gauges used by hydrological stations are either electric sensors for hydrostatic pressure or optical sensors. The hydrological monitoring system is of key importance for flood risk evaluation and for prevention of flood effects. 

Keeping the anodes wet and supplied with water is crucial. As pore water moves away from the anode by electroosmosis, makeup water must be available to prevent soil drying and burned-out anodes. Horizontal wells were installed along toe tops of the electrodes along with the steel bus bars. The cathode trench sloped toward a common sump at the east end of toe cathode. The sump also had lateral lines running to the north and south anodes. The anode trenches sloped from east to west and were constructed 6-in. deeper than the cathode trench. Hydraulically conductive wick drains were installed with the steel plate electrodes to allow free movement of water in or out of the electrodes as needed. The sump contained a level sensor to monitor the water level. The electroosmotic water flows from the cathode to the sump and then to each anode as needed by gravity. 

Industrial products Sensors for hydrauUcs, paint spray, agricultural sprays, refrigeration systems, air conditioning, water level... 

The CORIE observation network consists of multiple estuarine stations and one offshore station, each with a variable number of sensors. Most stations measure water levels, temperature, and salinity several stations measure velocity profiles and a few measure wind. Sampling intervals are in the 1- to 15-min range, with a sample consisting of the average over a short period (e.g., 30 sec) of measurements made at several Hertz. Most stations have telemetry, typically based on spread-spectrum radio. Selected stations have field computers, enabhng local storage and facilitating two-way communication. 

Typical safety-related systems employ pressure and level sensors which use small bore instrumentation lines. Most operating plants contain safety-related equipment and systems, parts of which are exposed to the ambient environment. These lines generally contain liquid (e.g., borated water) which is susceptible to freezing. Where systems or components and their associated instrumentation are exposed to sub-freezing temperatures, heat tracing and /or insulation is used to minimize the effects of cold temperatures. 

In summary, the ultrasonic level sensor is a simple device that is wall-mounted inside the IRWST, above the maximum water level. By adding this narrow range instrumentation, much of the error is eliminated, which allows the normal water level in the IRWST to be raised while maintaining the previous operating margin. This allows for increased water volume capacity, and thus, increased flood-up level post LOCA. 

---