Liquid Level Sensors Advantages in Level Measurement and Differences to Liquid Level Switches

As science and technology rapidly develop, various methods to measure liquid level have been invented, from rulers used in ancient time, to photoelectric, ultrasonic and radar gauges used by now. Liquid level sensor is a kind of pressure sensor measuring liquid level, which is suitable for level measurement in industries like petrochemical engineering, metallurgy, electricity, pharmacy, water supply and sewage, environmental protection and so on. For that the domestic market of magnetic flap level sensors developing continuously, the level sensor industry enjoys a bright future.
The reason for the wide application of level sensors attributes to the principle and features of the sensor.
Level sensors (static pressure liquid gauge / level transmitter / liquid level sensor / water level sensor) is a kind of pressure sensor that measures liquid level. Inputting type of static pressure level transmitter (liquid level gauge) adopts advanced isolated diffused-silicon sensitive elements or ceramic capacitor pressure-sensitive sensors from abroad. Based on the principle that the static pressure of tested liquid is in proportion to liquid level, the sensor transfers static pressure into electric signal, and convert it to standard electric signal (commonly 4~20mA/1~5VDC) by temperature compensation and linear modification.
Level sensors can transfer the variations of material level parameters into standard current signal, and remotely transmit to operation controlling room for centralized display, alarming or automatic control of secondary meters or computers. With its favorable structure and installation methods, the sensor is ideal for continuous measurement of liquid and material level  in special conditions like high temperature, high pressure, strong erosion, easy crystallization, blockage-proof, non-condensation and powdery or granular materials. Therefore this sensor can be applied for measurement and control in many industrial processes.
Level sensors and level switches are two kinds of most frequently used liquid or material level measurement devices, but few people understand the relation and difference between them, which is important for device selection. Now please allow we ISWeek to demonstrate the relationship between level sensors and level switches.
Difference between level sensors and level switches
Level switch is a kind of controller which opens inlet or outlet water valve according to signal output by level sensors to keep a constant water level. In other words, a level switch outputs a switch signal after confirming level height, and then level sensor transfers this signal into electric signal and output.
The electrical signal can be processed, such as connect to PLC data collector or professional display device to output liquid level. Although sharing the same working principle, a level switch is a switch controlling circuit, while a level sensor is a circuit component for voltage and current transformation.
For liquid level measurement, we ISWeek would like to recommend two kinds of products: photoelectric level sensor and level switch sensor.
What is a photoelectric level sensor?
Photoelectric level sensors is a new contact-type of level measurement and control device. It works with the principle of light reflection and refraction when going through an interface between two different mediums. For that it is featured with simple structure, high positional accuracy, no mechanical components, high sensitivity, corrosion resistance, and compact size, the sensor is gradually accepted by the market.

  1. despite of other parameters like temperature, pressure, density and electricity, level output is only related to whether the probe touches the liquid level.  Thus this sensor is featured with high detection accuracy, high repeatability, fast response and precise level control. This sensor needs no calibration and can be installed and use directly.
  2. with a relatively compact size, the photoelectric level sensing probe can be divided an installed in limited space, which means that it is suitable for use in spacial tanks. Also, several photoelectric sensors can be installed in a single object to form a multipoint level sensor or transforming controller.
  3. Since that inside the sensor,all elements are encapsulated with resin, and that there are no movable parts, this photoelectric liquid level sensor can be highly reliable, long-lasting without maintenance.

British SST low-cost Liquid Level SsensorsLLC200A3SH

Optomax Basic Series Liquid Level Sensors

LLC low-cost series liquid level sensors are used for single point. For mass OEM client, there is a special design containing an infrared emitter and a detector which are precisely located and installed to ensure that they can achieve perfect optical coupling in the air. When the conical end touches the liquid, IR light will transmit out of the conical surface, so that strength of the light reaches the detector will be weakened.
Features of low-cost photoelectric level sensor LLC200A3SH
(1)fast response,
(2)10mA driving current, photoelectric transistor switch output.
(3)working temperature:-20~85℃,M12 thread.
(4)lead: 250mm 24AWG,8mm, tin-plating.
Typical applications of low-cost photoelectric level sensor LLC200A3SH:
spring pool, leakage detection, automatic beverage dispenser, medical treatment, compressor, printer, water pump, household appliances, oil level monitor, HVAC, machine tool, high=low level switch, water level control, automotive electronics.
Electrical parameters of low-cost photoelectric level sensor LLC200A3SH

Supply voltage (Vs) At will
Supply current Nominal 10mA
Type of output Photoelectric tube (digital)
Output signal
Operating temperature 25 ~ 80°C
Storage temperature -30 °C ~ 85 °C

Ultrasonic Water Level Sensors Provide Real-time Flood Warnings in Iowa

To create the world’s most sophisticated flood monitoring and forecasting system, the Iowa Flood Center (IFC) uses more than 200 Senix ToughSonic 30 and ToughSonic 50 ultrasonic sensors to measure water levels in streams across the state. Data collected from the sensors are automatically sent to the Iowa Flood Information System (IFIS), where the real time monitoring information is integrated into an advanced hydrological model. System data and river stage hydrographs are shared with the public and emergency management officials.

With easy online access to the water level data from the sensors, Iowa residents and state agencies can now get the reliable, real-time information they need to manage flooding in their locales.

Ultrasonic sensors chosen for ruggedness and reliability

ToughSonic REMOTE 50 Ultrasonic Water Level Sensor

ToughSonic 50 Rear Mount water level sensor

The IFC needed a reliable and cost-effective way to get accurate, real-time stream-level readings. Project Engineer Daniel Ceynar decided to try Senix ultrasonic sensors because they had been used for years for water level measurement in the hydrology research labs at IIHR Hydroscience & Engineering at The University of Iowa. The University of Iowa has long been a world leader in hydrological research.

Senix ultrasonic sensors were selected because they are designed to easily integrate with other equipment; in this case with the system’s cellular modems, solar panels, on-board clock, and other equipment. Senix sensors also were also chosen for their ruggedness, programmability, and the reputation of Senix for excellent engineering support. “Senix sensors and the Senix technical team have been pivotal to the success of this project,” Ceynar said, noting that the IFC and Senix worked closely to design a special threaded collar for the ToughSonic 50 so it could be mounted to the IFC Stream Gauge enclosure using the same threading as the ToughSonic 30. That ToughSonic 50 Rear Mount model has since become a standard product for Senix.

The sensors are programmed for a measurement interval of between five minutes and an hour, using a boxcar average of a preset number of individual measurements. The system sleeps until it’s commanded to wake up to take measurement data and send it to the IFIS. Sensor data is provided using RS-485 serial data communications.

The entire IFIS flood warning system depends on the ruggedness and reliability of the Senix ToughSonic sensors and the IFC system. The Senix sensors are potted in water tight stainless steel housings and operate in 0-100% humidity over a temperature range of -40 to +70°C.

After assembly in the IFC lab, each stream gauge is submerged for three days to verify that it is water tight. This testing has proven useful. In the field numerous sensors have been submerged by flash flooding and once the flood waters subsided the sensors resumed sending correct stream level data without requiring any repairs.

“Once installed, the IFC stream gauges are practically 100% maintenance free,” Ceynar said. “Most stream gauge sites have not been re-visited since they were installed, 4+ years ago.”

Real-time water levels facilitate disaster management.

The Senix ToughSonic sensors have provided the IFC and the people of Iowa with critically important data for forecasting floods and managing the situation after flooding has begun. “The system—stream gauges and other Hydromet data—is routed through the IFIS where it is regularly used by all levels of government, law enforcement and the general public,” Ceynar said. “We’ve had first-hand experience working with our local emergency management coordinator during floods in 2013 and 2014 where we participated in the daily briefings using IFIS.” The stream gauges identify where the crest of the flood is located and track the crest as it approaches sensitive roads, bridges and towns.

Before the system was in place, it was common for emergency personnel to be dispatched to assess the flooding in threatened locations. But with the stream gauges collecting the data in real-time, emergency responders can focus on helping people instead of tracking flood waters.

See a video of a Stream Stage Sensor in action:

Iowa Flood Center a model for the world

Ceynar and his colleagues have been contacted by officials from other states, and from countries as far away as Australia. The stream gauges are also being evaluated by the Washington State Department of Transportation.

The State of Iowa is clearly on the forefront of flood control monitoring systems that allow everybody from private landowners to emergency personnel to make informed decisions during a flood event. “The IFC is the only flood center in the US, and IFIS is the only system of its kind that we are aware of,” Ceynar said. “We continue our efforts to create a National Flood Center.”

Senix is proud to work with innovative research and educational institutions like the University of Iowa both in the lab and in the field.

Application of Fluorescent Oxygen Sensors in Diffusion Type Oxygen Supply

High altitude anoxia has severe influence on people’s ability of thinking. At elevation of 1500m, the thinking ability starts to be affected, presented as restriction on new acquisition of complex intellectual activity. At 3000m, people’s thinking ability comprehensively decreases, especially in judgment. At 4000m, people would write clumsy handwriting in weird grammar. At elevation of over 5000m, people cannot concentrate on something like they usually do.
While the altitude increases, the atmosphere becomes thinner and the barometric pressure decreases accordingly, lowering the oxygen molecular number. (Please note that the above is talking about number of oxygen molecular, but not oxygen concentration.) Consequently, natural reactions of human body are intensified, leading to heart rate accelerates, reaction slows down, get emotional and immunity decreases, and causing symptoms like headache, ventosity, baldness, dyspnea, doldrums, lower sleep quality and hypomnesis. Being on plateau for long may induce high altitude heart disease, high altitude hypertension, or even acute lung or brain edema, which can possibly be lethal.
Under standard atmospheric pressure, the oxygen content in ambient atmosphere is about 21%(the percentage under standard conditions is 20.9%), and this is also the normal oxygen concentration for human beings who evolve for long and live on plain areas. The oxygen concentration keeps at about 21% from sea level to upper air over altitude of 10000 meters.

What is it for?
That People get oxygen deficit on plateau where oxygen concentration is 21%?
It’s for that at different altitudes,
The oxygen partial pressure differs greatly.
On plateau, the air is thinner (total air pressure is relatively low), so although the oxygen concentration is the same, the partial pressure is lower than that in plain area. That’s why people get anoxia on highland. Most of us think only about oxygen concentration of oxygen(% vol). Now after understanding the difference and linkage between oxygen partial pressure and concentration, we can touch the truth of plateau anoxia.
Then, how can people adapt to the plateau oxygen-deficient environment? In this case oxygen fraction indoor shall be increased to improve the oxygen volume fraction in the air.
In recent years, the concept of diffusion type oxygen supply has been raised, and has been realized indoor by pressure swing absorbtion oxygenerator or liquid oxygen evaporator, as a solution for plateau oxygen-deficient problem. By installing indoor control systems, the oxygen concentration can be automatically adjusted.
When interior oxygen concentration reaches the upper limit (26%), oxygen supply system is automatically shut off; when oxygen enrichment is lower than the lower limit, the system is automatically started.
Therefore, it will be very important to monitor interior oxygen enrichment (which is based on oxygen partial pressure). For now most diffusion oxygen generating systems and oxygen enrichment systems are based on electro-chemical principles. However, the lifespan of electro-chemical oxygen sensors are relatively short, and the output of these sensors will attenuate with time goes by. This is a severe drawback that limits the development of such technology.
The oxygen sensor for diffusion oxygen generating system is required for high accuracy, high repeatability, long lifespan and no pressure dependence. It should also be easy to use and needs few maintenance and calibration. To meet these demands, SST company in Britain has developed oxygen sensor Lox – 02, which is based on principle of fluorescence quenching.

LuminOx Fluorescence Optical Oxygen Sensor (O2 Sensor)
The fluorescent oxygen sensor is designed based on principle of fluorescence quenching. Oxygen absorbs the blue part of spectrum in ray of light. Fluorescence of the special ruthenium compound stimulated by oxygen gets quenched, so that the strength of light is changed in relation to oxygen enrichment. Detection based on principle of optic oxygen, such sensors has no effects on ambient gas to be detected, and consumes no oxygen, which is greatly different from conventional oxygen sensors which consumes oxygen and change the proportion of ingredients of tested gas. Accurate value of oxygen partial pressure can be obtained by demarcating the time that strength of light is changed, and this value will not be influenced by pressure change. During demarcating the oxygen concentration, the sensor is completely inert and has no consumption on oxygen to be detected, while, the implanted pressure chip and software has calculated the concentration value. To read the value of oxygen partial pressure, barometric pressure and oxygen concentration, only a command is needed.

The Operating Principle & Application prospect of Hydrogen Fuel Cell

On March 5th, the first session of the 13th NPC was held in Beijing. In the government work report, the prime minister clearly mentioned that preferential policies for vehicle purchase tax of new-energy vehicles would be prolonged for three years, and restriction policies on second-hand vehicle migration would be comprehensively canceled. Undoubtedly, the development of new-energy vehicle has become an important trend of future automobile industry, but whether electric vehicle or hydrogen cell vehicle will take up the mainstream is still under discussion. Today let’s talk about one of the future development directions of new energy resources — hydrogen fuel cell.

The basic principle of hydrogen fuel cell is that: by the reverse reaction of water electrolysis, hydrogen and oxygen are respectively served to the anode and cathode. Hydrogen out diffuse from anode and react with electrolyte, and then released electrodes reach cathode through external load. The hydrogen fuel cell is a power generating device which transfers the chemical energy in fuel and oxidizing agent into electric energy. Outwardly, with anode, cathode and electrolyte, it seems like an accumulator, but substantially a hydrogen cell needs no recharging, but only hydrogenation. For instance, the battery of a simple electric vehicle is like a power preservation station, while a hydrogen cell is like a power generating station.

Operating principle of hydrogen fuel cell

By far, vehicle manufacturers are strongly promoting their electric vehicles, but there are two main problems faced by all-electric cars:

  1. Long waiting time. The electric vehicle needs to be charged before starting. Even by rapid charge, it takes at least 20 minutes waiting, which is hard to bear for most drivers.
  2. Lifespan and recycle of batteries. Commonly the lifespan of a lithium-ion battery is about 20 years, but due to the particularity of new-energy vehicles, when the battery capacity fades by 80%, the vehicle’s endurance mileage will significantly decrease. It means that in about 5 years, the batteries must be replaced. Whereas the recycle of batteries, requires high cost and tough technological problems, which urgently needs to be resolved. According to the prediction made by China Automotive Technology & Research Center, considering factors like car scrappage term and power battery life, between 2018 to 2020, the accumulative number of scrapped power batteries nationwide will reach a scale of 350 thousand tons.

On Feb. 26th, 2018, seven ministries including Ministry of Industry and Information Technology and Ministry of Science and Technology have jointly issued Interim Procedures of Power Storage Batteries Recycling Management of New-energy Automobiles. The involvement of policies will make positive contribution to the regulation of development of this industry, the integrated utilization of resources and the protection of the environment and human health, so as to push forward the sustainable and healthy development of new-energy vehicle industry.

A vehicle powered by hydrogen fuel cell is featured with high energy conversion efficiency, long lifespan, smooth performance, while its greatest advantage is that it has no pollution emission. Hydrogenation time for such vehicles in mass production now are within 3-7 minutes, which is the same as that for oil-fueled automobiles.

Hydrogen leakage may occur inside the hydrogen fuel cell during use. When the concentration of hydrogen reaches a certain point, it will cause explosion and lead to safety accidents. To avoid such things from happening, it is advisable to implant a hydrogen module in the cell, which can measure hydrogen concentration in real-time and give an alarm when the concentration reaches the safety range to warn the car driver.

We ISweek supply hydrogen module FSM-10H-01 (semi-conductive principle) with our profession. The features of this module are as follows.

  1. Small in size
  2. Low cost
  3. Factory calibrated
  4. Conform to requirements of RoHS
  5. RS485 output of digital signal in proportion to gas concentration
Pre-calibrated Combustible Gas Sensor Module


The Application of Combustible Gas Sensor in Urban Gas System


In this rapidly developing era, the demand of natural gas is driving the prosperity of whole gas meter industry. From the prospective of end-users, the popularity of urban gas is improving with the growth of urbanization and urban population, and thus the demand of natural gas for industrial use and domestic use will significantly increase. From the prospective of market opportunity, the increasing demand of domestic and industrial used natural gas is boosting the demand of gas meter. The huge market space has become a powerful driving force on gas meter industry.
Among 600 cities nationwide, only about 300 cities have laid natural gas pipeline. From now on, with the planning and construction of line three and line four of west-east gas pipeline project, the construction of regional and urban pipeline will develop in a rapid speed.
In order to ensure the safety of living, production, fabrication, transport and using, it’s very important to detect and monitor gas leakage and anti-explosion on each process. Meanwhile, relevant government bureaus have formulated standards of monitoring, and have entrusted Shenyang Fire Research Station in Ministry of Public Security to implement of publicizing, acceptance inspection and check of the corresponding standards.
For now, detection methods toward gas industry are:
Household use combustible gas is detected mainly by semi-conductor and planar semi-conductor elements, which primarily detects in the range of 0-10000ppm. The mainstream market is taken up by domestic products. Municipal administrative gas company majorly adopts catalysis elements which mainly detects in the range of 100%LEL. These elements are predominantly used on the storage, transportation and pipeline safety polling of gas, etc. Since 2007, IR gas sensors with proprietary brands start to appear in domestic market, thus IR gas sensors are gradually adopted as high-end gas detection products in gas industry. They are able to detect 100%LEL and 100%VOL. Especially, laser correlation technology can be applied in long distance polling in gas industry.
We ISWeek are glad to supply the semi-conductive sensor TGS2611 and its module FSM-T-01, the features of these products are as follows:

Features of TGS2611:

  1. Quick response
  2. High sensitivity
  3. Strong resistance against interference
  4. Long lifespan of 5 years
日本figaro 可燃气体传感器

Features of Pre-calibrated Methane Gas Sensor Module FSM-T-01:

  1. Adapt for sensor TGS2611
  2. Factory calibrated and temperature compensated
  3. Programmable setting alarm point output
  4. Gas concentration is quantitatively output in RS485 digital signal
  5. Compact size and low cost
Pre-calibrated Methane Gas Sensor Module

Which is Better? Submersible Galvanic Dissolved Oxygen Sensor VS Yuasa Dissolved Oxygen Sensor!

With the development of science and IT technology, the society is being covered by the Internet of Things in a rapid manner. Sensors, as one of the most important element in this IoT society, are playing an essential role in interconnection. Being an indispensable type, dissolved oxygen sensors are applied quite widely.
Now we ISweek would like to make a detailed comparison between two types of DO sensors by the following two models for reference: Submersible galvanic dissolved oxygen sensor DO6400 and Yuasa dissolved oxygen Sensor KDS-25B.

Submersible Galvanic Dissolved Oxygen Sensor


The DO6400 & 7400 series dissolved oxygen sensors feature a large capacity electrolyte holder, positive fit, easy to replace membrane and dependable galvanic cell technology for long term deployment. The body design ensures a good grip when wet. Ideal for Aquaculture and waste-water monitoring applications, these sensors require minimal maintenance. PTFE or High-Density Polyethylene (HDPE) membranes are available. 2 Replacement membranes, installation tool and electrolyte are included. Additional maintenance parts are in convenient kits (see ordering information). Sensors with mV output as well as built-in 4-20mA output in 0-100% and 0-200% saturation range are available.
Specifications of DO6400:

O2 Measuring Range DO6400, DO6400TC (0.5-20ppm), DO6441(0-100%),
DO6442(0-200%), DO7400, DO7400TC (0.03-20ppm),
DO7441(0-100%), DO7442(0-200%)
Body Material Noryl
Cathode Silver
Anode Zinc (DO6400 Series), Lead (DO7400 Series)
Maximum Temperature 50 Degrees C
Power Requirement 12-36V DC (for models DO6441, DO6442, DO7441 and DO7442 only )
Temperature Sensor (User specified temperature elements) Connect to your controller or PLC for temperature output
Cable length 3 meters, tinned leads
Minimum Flow rate 3 cm per second

The GS Yuasa Dissolved Oxygen Sensor KDS-25B is a unique galvanic cell type sensor which was developed for water quality control. Its most notable features are long life expectancy and no influence by CO2.
DO sensor KDS-25B uses special acid electrode. Its cathode adopts inert metal gold, and its anode is of metallic lead. Oxygen diffuse and pass through fluororesin film to take part in redox reaction. In this way an oxygen lead accumulator is constituted. The current generated in the redox is transferred into voltage output by internal resistance. In this process, the current generated is directly proportional to the concentration of dissolved oxygen, or strictly speaking, to oxygen pressure. (the higher the content of dissolve oxygen is, the more oxygen molecules getting through the film and taking part in redox reaction are). KDS-25B is a favorable choice for environmental monitoring and water quality detection.
Specifications of KDS-25B DO sensor:

These two types of DO sensors are both of excellent performance, making them ideal choice for industries like aquaculture, environmental monitoring and sewage detection and treatment. Both of these DO sensors have their merits in function, offering users with more options in line with their practical demands.

The Application of Water Quality Sensor in Aquaculture

Sensor is a kind of common detection device which is able to transfer the signal of detected object into electric signal in a certain rule for output, storage or logging. Sensors can be applied in a wide range including industry, chemical engineering, electric power, electronics, machine tool and agriculture. Water quality sensors, or say water quality probes, are commonly used in aquaculture and are playing important roles.

Aquaculture farms can be seen almost everywhere in coastal cities. Only in an environment that suits yield, can people get good harvest of various aqua organisms including fishes, mussels and other aquatic species. Water quality, as one of the most important factors that influence aquatic yield, can be monitored by sensors.
There are quite a lot of elements to be detected for water quality, among which most important ones are the temperature, oxygen content and noxious gas content of the water. In the past, farmers can estimate these factors with their experience, but with the rapid development of sensing technology, now they can use sensors to monitor water quality. For instance, water temperature can be measured by temperature sensors, PH value can be measured by PH meters, oxygen content in the water can be measured by dissolved oxygen sensors, and the content of noxious gas can be measured by some other sensors.
As science and technology develop, more and more sensors are applied for aquaculture. There are antiviral sensors to detect whether water is poisoned and aquatic product density sensors to ensure the healthy growth by proper methods.
Different types of sensors can be applied for different aquatic species according to their requirements on water quality. For those that have high demand on temperature, temperature sensors must be applied. For those that are demanding on dissolved oxygen, DO sensors must be used to monitor oxygen content in the water. The effect of geographic position shall also be considered. In a word, to guarantee the good aquatic harvest, optimal design shall be applied.

The automatic IoT aquaculture monitoring system includes sorts of water quality probes and sensors which can monitor water temperature, salt content, pH value, dissolved oxygen and other parameters needed for aquatic farming. Also, fixed underwater camera can be installed in cultivation areas to monitor the cultivation conditions. With videos the system can send out early warnings for any emergency, so as to lower labor cost significantly, and thus realize front-to-end automation of aquaculture.

Dissolved oxygen sensor recommended by isweek:

Comprehensive monitoring system for modern aquaculture

With the advance of economy level, people’s living standard has also been increased, the demand for aquatic products is becoming greater and greater, more and more people are engaged in aquaculture business and the scale of this industry keeps showing an rising trend, meanwhile the types of aquatic products have also become very diversified.

So generally the traditional breeding method for aquaculture is to judge whether there is enough oxygen in water by observing the floating heads condition of fishes and shrimps, to decide the contents of ammonia nitrogen according to the turbidity of water, to judge the pH value and temperature of the water based on experience, so as to start the aeration device manually. However, with the development of consumer market and the extension of the scale of aquaculture, more and more issues arise from this traditional breeding way of aquaculture. The key factors that affecting the environment of aquaculture are temperature, light, dissolved oxygen, ammonia nitrogen, sulfides, nitrites, pH value and so on. Such factors are intangible so it is difficult to accurately control them, and if only by depending on experience to judge, the error would be quite significant. Besides, as the scale of aquaculture is becoming larger and larger, purely relying on this traditional method seems to be more and more powerless; any carelessness would possibly lead to heavy losses.


For the above reason the writer hereby would like to introduce to you a large distributive type remote and comprehensive monitoring & management system for aquaculture. So the system is based on computer hardware with software processing being its core part, it has multiple sensors’ signal acquisition systems, automatically controlled aeration system, field video acquisition system, sound and light alarm system, SMS warning notice system as auxiliary parts, collecting multiple parameters for computer processing, fixing issues when abnormal conditions appear. For example, the aeration system would be initiated if there is a lack of oxygen; the heating system would be started if the water temperature is too low; you would be warned with SMS to adjust the alkalinity and acidity if water’s pH value deviates. Even that when alarm sounds the video of the field where the problem occurs could prompt out; you would be able to observe the condition in the field, so as to take efficient counter measures. For all these situations, you don’t really have to be present on the field, but will be able to master them clearly. Through the Internet you can control them at home or elsewhere remotely; such kind of system is very suitable for monitoring and management of large aquaculture.

The major functions and characteristics of the system are as follows, you can choose whatever functions based on your requirements. In order to save costs, you don’t have to configure all of them:

1) Field video function: using IP cameras to gather the situation of different pools (two types of camera, namely above water and under water cameras can be used), enabling all weather video recording;

2) Water temperature control function: collecting and processing water temperature signals of every pool, automatically start heating system once the water shows low temperature;

3) Function of controlling oxygen in water: the scientific name of oxygen in water is dissolved oxygen, by using the dissolved oxygen sensor the concentration signals of dissolved oxygen could be captured and treated, when the level of this parameter goes down to the lower limit the aeration system would be initiated;

4) Function of automatic control of liquid level: when the liquid level in the pool is less than the lower limit, the pumping equipment would be activated; once the pool is filled with enough water the equipment would stop automatically. The liquid level of the pond can be shown at any time, when the level surpasses the higher limit, the alarm would also be triggered, so as to prevent the damage caused by floods or other disasters.

5) Function of automatic monitoring of flow: to monitor the water flow of the pond at any time, when the flow rate becomes too small to meet the needs, alarm would be triggered or pumping equipment would be initiated, which is very suitable for ponds which need constant injection of water.

6) Depending on relevant sensors such as water quality sensor, water pH sensor etc chosen, the signals of light, ammonia nitrogen, sulfide, nitrite and pH value can be collected and processed.

7) Infrared radiation function: once there is a suspicious person entering the field, the video would record this and the alarm would be triggered, so as to prevent the happenings of unidentified people stealing fishes, turtles and other precious species, criminals poisoning the ponds or children intruding the spot and falling into the ponds and other undesirable phenomena.

8) Function of locating field position: the video will show the positioning once abnormal situation occurred.

9) Function of alarm with sound and picture: when undesired phenomenon happens, the video and content of the incident would prompt out on the computers in the control room, meanwhile there would also be sound alarm.

10) Distributed sound and light alarm function: sound and light alarm can be installed at place where alarm reminding is needed, such as field alarm, so as to solve the issue in no time.

11) SMS warning function: when abnormal situation happens, the info would be sent to your mobile. Even you are not in the field, you could still have a knowledge of the condition at any time.

12) Internet function: when you are not present at the spot but want to know the condition there, the Internet function is needed, by using this function you could master all the sensors’ info and videos’ signals.

13) Customized functions in order to meet specific needs.

Speaking of computer hardware before, people tend to think it is a kind of high technology, with prohibitive price of several hundred thousand, several millions to tens of millions. However, with the advancement of technology, computers are no longer that mysterious, and they are applied in people’s daily life at any moment. Our company has developed this very system for aquaculture with reasonable price and flexible configuration options. There is no doubt that you can buy some of the hardware equipments in your local area, but they have to meet the system’s demands, by doing this the commissioning cost can be save and also the maintenance would be relatively convenient. Of course we could offer to purchase all the systems for you, it’s all up to you to decide. We will debug all the devices we provide in the field until they work as expected.

The Applications of CO Sensor in Fire Alarm

It is known to all that when a fire happens, the combustion products mainly are CO, CO2 and H2O. These products appear much earlier than burning smoke (scores of minutes to couple of hours). Unlike the smoke particles in fire smoke, gas needs much less heat driving to rise rapidly. Due to the influence of ambient humidity, commonly H2O is not considered as a fire detection parameter. CO is a special sign of fire appearing in very early stage. Normally the air contains very little CO. Even in places where contains more CO, such as kitchens, the content is still under 20ppm. However in a fire, the sufficient burning of almost every material will produce CO, especially in smoldering combustion. From the start of fire to violent flaming, CO is generated from none, accumulated, and gradually decrease in a regular manner. Moreover, the density of CO is lower than air, making it easier to floating to fire detector in the ceiling so as to get advanced warning. Generally, fake source of fire generates no or very little CO, thus CO is ideal indicator for advanced fire detection. It is very important for the arrangement of detectors and information capture of early stage of fire.
On the production of CO, there have been many researches worldwide. For example, in 1994 Jackson and Kobins experimentally measured the max production of CO in unit area of 6 kinds of EN fire: open fire of woods, wood pyrolysis, smolder fire of cotton, open fire of polyurethane plastic foam and normal heptane open fire.
Also, in his experiment in 1997, Pfister monitored the changing process of CO production in several standard fire. In the period after the fire happens, the concentration of CO arises, apparently higher than the ambient concentration before the fire.
In order to evaluate the adaptability to various kinds of fire of the pattern, British researchers implemented control experiment on 7 kinds of detectors, including CO sensors, temperature sensing detectors and light beam type smoke sensing detectors, with 6 sorts of EN fire. The experiment shows that CO sensor, among the seven, is the only detector that respond to all 6 kinds of test fire.
The British researchers did combustion tests in enclosed area (fire in sealed closet and waste-paper basket). At 25min before any smoke sensing detectors responded, the concentration of CO produced in the fire had reached 50 ppm, and thus CO sensor was able to respond.
Furthermore, real fire condition tests indicates that, in most cases, including those with forced ventilation, CO can be a favorable fire indicating gas. When fire appears in the form of smoldering, like those in residential area or offices, CO would be the best indicator, for that CO can reach valid concentration in hours before smoke can be detected.
Previously, the application of CO sensors was limited by people’s low awareness and its drawbacks of low sensitivity, high power consumption and high cost. In recent years, breakthroughs are made in CO sensing technology, for instance, its power consumption is significantly lowered, while sensitivity and lifespan is improved.
At present, we ISWeek are glad to supply two types of CO sensors, TGS5141 and TGS5042. The details are as follows:

日本FIGARO 纽扣式一氧化碳传感器(CO传感器)
Features of CO Sensor TGS5141:

  1. Ultra compact, similar to a cell battery in size
  2. Battery driven available
  3. High selectivity/ repeatability to CO
  4. High linear output feature to CO
  5. Easy calibration
  6. Long lifespan
  7. UL certified
  8. Conform to requirements in UL2034, EN50291 & EN54-31
日本figaro 民用电化学一氧化碳传感器

Features of CO Sensor TGS5042:

  1. Battery driven available
  2. High selectivity/ repeatability to CO
  3. High linear output feature to CO
  4. Easy calibration
  5. Long lifespan
  6. UL certified
  7. Conform to requirements in UL2034, EN50291 & RoHS.

Classification and Operation Principle of Optic Fiber Temperature Sensors

Optic fiber temperature sensor is a sensing device that analyze the spectrum transmitted by the optical fiber to obtain real-time temperature. Its operation bases on that for some materials, spectrum absorbed changes with temperature. These sensors mainly includes optic fibers, spectrum analyzer and transparent crystals, etc., and can be divided into distributed type and fiber optic fluorescence type.

Distributed optic fiber:
This type is often used in a system that detects distribution of temperature in a room. Its operation principle was first raised in 1981, and was developed for years into the technology we adopt today. This development is based on three researches about sensors: Rayleigh scattering, Brillouin scattering, and Raman scattering. Great achievements have been made on research about Rayleigh scattering and Brillouin scattering (OTDR), so in the future, more attention will be paid on research about new distributed type of optic fiber sensors based on Raman scattering.
Optic fiber fluorescence:
At present, most heated research is about optic fiber fluorescence temperature sensors, which uses fluorescent material’s feature of luminescence to detect the temperature of light area. When being stimulated by IR or UV light, this material will give out light whose parameters have positive connection with temperature, thus the temperature can be measured by testing fluorescence intensity.
Optic fiber temperature sensors have macro-molecule temperature-sensitive material that matches the refractive index of optic fiber coated on two welded optic fiber. This enables the light to be input from a fiber and then be output from another. Since that the refractive index of this new temperature-sensitive material is affected by temperature, the output luminous power has functional relationship with temperature. The physical essence of the sensor is that characteristic parameters of light-wave transmitted by optic fibers, like amplitude, phase, polarization state, wavelength and mode, are sensitive towards ambient factors like temperature, pressure and radiation, etc. It’s a kind of non-contact temperature measurement.
The operation principle of optic fiber temperature sensor is: in low temperature zone(under 400 ℃) where radioactive signal is weak, the system enables light emitting diode(LED) and the fluorescence temperature measurement system starts to work. The excitation light from LED goes through collecting lens and get coupling to the branch end of Y type optical fiber, and then couples to the temperature sensing probe through optical fiber. Being triggered by excitation light, the top of optical fiber sensing probe emits fluorescence light. This fluorescence signal is derived by optic fiber, emitted from the other branch of the optical fiber coupler, and received by photoelectric detector. The optical signal output by the photoelectric detector is amplified and processed by fluorescence signal processing system to calculate fluorescent lifetime, so as to obtain the measured temperature. In high temperature zone(over 400 ℃) where radiation signal is strong enough, the radiation temperature measurement system start to work and luminous diode is off. The radiation signal passes through sapphire optic fiber and get output from Y type fiber, and then be transferred into electric signal. The system measures the strength of the radiation signal to calculate the detected temperature.

ISWeek, the famous online mall of all kinds of sensors, has imported three types of optic fiber temperature sensors from Canada, all of which are of excellent quality and performance. These imported sensors are: Type FOT-L-BA and Type FOT-L-SD, which are ideal for temperature measurement in extreme environment; and Type FOT-HERO, which is specially designed for temperature measurement in electronic explosive environment. These sensors can be applied in various industries.
The top of optical fiber’s sensing probe, whose length is 8 to10mm, is Cr3+ ion-doped, so as to realize fluorescence emission when getting light excitation. Meanwhile the external surface of the top of the fiber is plated with blackbody chamber for radiation temperature measurement. (To satisfy blackbody chamber’s requirement of constant apparent radiance, the ratio between the length of blackbody chamber and diameter of the optical fiber is larger than 10.) In order to assure the performance of the whole system, it’s essential to avoid or reduce the mutual interference between fluorescent emission part and thermal radiation part.
It can be found out that the interference can be mainly presented as:

  1. the background signal of fluorescent signal has influence on accuracy of fluorescence lifespan detection;
  2. Surface plating of optical fiber has influence on strength of fluorescence;

3) Cr3+ ion-doping in optical fiber has influence on thermal radiation signal of blackbody chamber.
Many colleges and universities worldwide have researches on such sensors. For example, Hansung University in Korea found out that for 10cm of double-doping optical fiber, temperature index corresponding to the fluorescent strength of reflection at its 915nm point is 20℃~290℃; Study in Tsinghua University uses semi-conducting GaAs material to absorb light. Based on the principle that light changes with temperature, the study has developed an optical fiber fluorescent temperature sensor whose temperature range is 0℃~160℃.