Why use an SO2 sensor?

Why use an SO2 sensor?

Sulfur Dioxide gas (SO2) is a toxic gas with a strong irritating smell. It is present at very low concentrations in the atmosphere and is naturally emitted during volcanic eruptions. Inhaling sulfur dioxide has been associated with respiratory disease and difficulty breathing. It is also a precursor to acid rain and atmospheric particulates. Sulfur dioxide gas can be an active component or a waste product of several different industrial processes.

Atmospheric Sulfur Dioxide

Fossil fuel combustion at power plants is the largest emission source of sulfur dioxide into the atmosphere. Other sources include extracting metal from ore and the burning of high sulfur containing fuels by ships, trains and machinery. Perimeter monitoring at industrial sites is common to measure the concentration of sulfur dioxide being emitted into the atmosphere. isweek offer both fixed and portable monitors with an SO2 sensor suitable for long term outdoor perimeter monitoring as well as shorter term human exposure studies.

Industrial Uses of Sulfur Dioxide

Sulfur dioxide is an intermediate component in the formation of sulfuric acid. Sulfuric acid is a very important commodity chemical used in several industrial processes including the removal of oxidation and rust from metal sheeting. Sulfur dioxide gas is also used directly in many industries. It acts as a preservative for dried fruits due to its antimicrobial properties and is used in wine making to protect the wine from spoilage. isweek can provide a range of instruments for industrial monitoring of sulfur dioxide.

isweek SO2-B4 Sulfur Dioxide Sensor SO2 Sensor 
Alphasense Sulfur Dioxide gas sensors operate using proven fuel cell technology.

Sensors are available in the following sizes:
A: 20mm diameter, the industry standard size for portable gas detectors
B: 32mm diameter package, the best choice for fixed site applications
D: miniature, with proven long-term performance. Sensors designed for the next generation of portable gas detectors.

The SO2 range provides OEMs with reliable sensors for use in a variety of applications. Strong signal levels combined with low zero current allows resolution below 1ppm and an operating range for safety applications up to 2,000ppm. The sensors are designed for use in both fixed site and portable instrumentation.

The SO2 sensors offer our electrolyte leak-free guarantee and reliable long-term detection performance. The leakproof housing is moulded with a colour coded top for ease of identification.

Things to Consider When Buying Carbon Monoxide Sensors

Things to Consider When Buying Carbon Monoxide Sensors

Before you buy, it’s good to break down exactly what to look for in a carbon monoxide Sensor. We’ll highlight several key factors that were part of our decision-making process to help you become a more informed consumer, but if you’d like to skip to the details on our recommended models, you can do that here.

What Are the Symptoms of Carbon Monoxide Poisoning?

Carbon Monoxide doesn’t have a smell or taste, so you might not know right away that you’re being poisoned, but your body will. If you have carbon monoxide poisoning, you may feel dizzy, become nauseous, throw up, develop a headache, get confused, or pass out. It’s often been said that the signs of CO poisoning might resemble the flu.
Every year, 400 Americans die from accidental carbon monoxide poisoning (from fuel burning, not fires), and 20,000 are admitted to the emergency room.1 If you become unconscious while carbon monoxide is filling your home, it can be life threatening. That's where carbon monoxide Sensors come into play. Once installed, they can alert you about high levels of carbon monoxide in your home, which will give you more time to get to safety.

Who Is Most Susceptible to CO Poisoning?

Everyone is susceptible to carbon monoxide poisoning. But, according to the Centers for Disease Control and Prevention (CDC), children, older adults, people who are physically ill, and pets are more likely to be affected by CO.2 The Mayo Clinic adds that unborn babies’ blood cells take in more CO than adult blood cells, which makes them more susceptible to poisoning.3 Older adults who experience high levels of CO could be more likely to incur brain damage.
When it comes down to it, a CO Sensor can help save your life and the lives of the people you love.

What to Do If You Suspect High Levels of Carbon Monoxide

If you or your family members experience carbon monoxide poisoning symptoms, quickly walk outside for fresh air and call 911. Even if you start to feel better, you can still have toxic levels of CO in your system and might require medical help. In this situation, it’s a good idea to have your whole family checked for poisoning, including your pets. Signs of carbon monoxide poisoning don’t always happen right away—it can happen over the period of days and possibly even weeks, depending on the levels of CO in your home.

What Is a Carbon Monoxide Sensor?

Carbon monoxide Sensors are a lot like smoke Sensors, but instead of looking for signs of fire, they detect levels of carbon monoxide. Depending on the brand, Sensors operate in one of three ways: with a biomimetic sensor, metal oxide semiconductor, or electrochemical sensor.
Biomimetic Sensors use gels that change color after absorbing a certain amount of carbon monoxide—and then a sensor sounds an alarm. Metal oxide semiconductors have silica chips that detect CO and send electrical signals to trigger an alarm. Electrochemical sensors are considered to be the best in the industry. They use electrodes in chemical solutions that sense changes in electrical currents when carbon monoxide is present, and they sound an alarm.
If you have a professionally monitored security system installed, it should come with a CO Sensor.

Where to Install Carbon Monoxide Sensors

The Consumer Product Safety Commission recommends putting a carbon monoxide Sensor outside every separate sleeping area in your home.4 You might also want to add a carbon monoxide Sensor in your kitchen and basement for added safety. Also, make sure you install Sensors close to bedrooms so alarms will wake you up if you're sleeping.
If you have an attached garage, you’ll want to place a CO Sensor by the entranceway. A vehicle that’s been left running in a closed space is a common cause for CO poisoning. In the grand scheme of things, it’s better to be overly cautious by placing CO Sensors in every room, floor, and hallway than suffering CO poisoning.

How to Maintain a Carbon Monoxide Sensor

Most carbon monoxide Sensors last an average of five years. Although the product’s lifetime will vary depending on your make and model, you can still get the most out of your Sensor by wiping it down weekly to keep it clean from dust and debris.
It’s also a good idea to test your CO Sensor monthly. Start by pressing the “test” button to ensure the siren works. If your Sensor is older, you can purchase a carbon monoxide test kit to ensure that it’s fully functional. If the Sensor doesn’t go off when you test it, it’s probably time to buy a new one.

How Liquid Level Sensors Work

Level sensors are used to monitor and regulate levels of a particular free-flowing substance within a contained space. These substances are usually liquid, however level sensors can also be used to monitor some solids such as powdered substances. Level sensors are widely used industrially. Cars use liquid level sensors to monitor a variety of liquids, including fuel, oil and occasionally also specialist fluids such as power steering fluid. They can also be found in industrial storage tanks, for slurries, and in household appliances such as coffee machines. Basic level sensors can be used to identify the point at which a liquid falls below a minimum or rises above a maximum level. Many sensors can detail the specific amount of liquid in a container relative to the minimum/maximum levels, to provide a continuous measurement of volume.
There are a number of different types of liquid level sensor used to detect the point level of a liquid. Some types use a magnetic float, which rise and fall with the liquid in the container. Once the liquid, and by extension, the magnet, reach a certain level, a reed magnetic switch is activated. Commonly, there is a switch towards the top and the bottom of the container, allowing detection of minimum and maximum levels of liquid. Many sensors also include a protective shield to protect the magnet from turbulence or interference from direct contact with the liquid.
Another common type of level sensor is known as a Conductive sensor. Only liquids which conduct electricity can be used in this sensor. This type of sensor includes a source of power, usually of a fairly low voltage. At least two electrodes are placed within the container. When a conductive liquid reaches a certain point, it will come into contact with both a longer and a shorter electrode, and thus complete a circuit and activate an internal switch.
Pneumatic sensors are also a fairly common occurrence with particularly hazardous liquids, or in systems where the use of electricity is not viable or possible. This is because the sensor itself does not come into direct contact with the liquid at all. The sensor detects the level of air between the liquid and the pneumatic sensor, then uses this to calculate the amount of liquid used to fill the remainder of the container. These types of sensors are also relatively cost-effective.
There are also other types of level sensors which offer continuous measurement of liquids. Magnetostrictive sensors are similar in design to regular magnetic float sensors, yet the magnet level is measured using a magnetostrictive wire, which will react when its magnetic field is interrupted by the presence of the magnet. The exact point at which this interruption occurs can be determined by the distance between the bottom of the wire and the point of interference. Alternatives to this design include a magnetoresistive sensor, whereby an additional magnet is inserted onto the arm of the float, allowing accurate triangulation of the exact position of the magnets. This type of sensor is commonly used in conjunction with computer programs due to its accuracy.
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  Optomax Industrial Glass Series Liquid Level Switches - LLG810D3-003

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  LLG210D3L24-00x Optomax Industrial Glass Series Liquid Level Switches that can detect almost any liquid type; oil or water based.
  

LuminOx Fluorescence Optical Oxygen Sensor With Evaluation Interface Board

LuminOx Fluorescence Optical Oxygen Sensor (O2 Sensor) - LOX-02

LOX-02 LuminOx Fluorescence Optical Oxygen Sensor (O2 Sensor) description
The LuminOx Family is a range of factory calibrated optical sensors which measure ambient O2 levels using the principle of fluorescence quenching by oxygen.
Our unique patented process allows us to produce an oxygen sensor that benefits from low power, traditionally associated with electrochemical sensing devices, while providing a much longer lifetime due to the non-depleting sensing principle.
LuminOx unlike other sensor technologies is stable and robust, it is RoHS compliant as it does not contain lead or any other hazardous materials and has negligible cross sensitivity.
LuminOx can be purchased as a single optical sensor, or as part as an evaluation kit which includes the LuminOx Sensor Evaluation Interface Board, which was designed to allow customers to easily evaluate the sensor with minimum effort or design work. 


LOX-02 LuminOx Fluorescence Optical Oxygen Sensor (O2 Sensor) BENEFITS
• Low power
• Can also measure O 2 % & barometric pressure
• Suitable for battery power use
• Long life
• High accuracy
• Small & compact
• Low cost
• Maintenance free
• Contains no hazardous materials
• Connects directly to microcontroller without any additional circuitry.
• Factory Calibrated

LOX-02 LuminOx Fluorescence Optical Oxygen Sensor (O2 Sensor) APPLICATIONS
• Oxygen Detection
• Portable Equipment
• Breathing Apparatus
• Inerting
• Medical
• Lab Equipment
• Agriculture
• Incubation
• Fire Prevention
• Flue Gas in Condensing Boilers

LuminOx Optical Oxygen Sensor Evaluation Interface Board - LOX-EVB

LOX-EVB LuminOx Optical Oxygen Sensor Evaluation Interface Board GENERAL DESCRIPTION
The LuminOx Sensor family is a range of factory calibrated oxygen sensors which measure ambient ppO₂ levels using the principle of fluorescence quenching by oxygen.
The LuminOx Evaluation interface Board has been designed to allow customers to quickly and easily evaluate the sensor with the minimum of effort or design work
The LuminOx Evaluation Kit simultaneously provides three outputs;
• RS232 (serial interface voltage levels)
• RS485 (Modbus RTU) port allows multiple sensors to be addressed on a bus
• 0-5V Analogue output for basic measurements of oxygen only

LOX-EVB LuminOx Optical Oxygen Sensor Evaluation Interface Board BENEFITS
• Converts the LuminOx TTL level
• RS232 output into 3 standard industrial outputs
• Auto detects ppO2 or O2% variants of LuminOx Sensor.

LOX-EVB LuminOx Optical Oxygen Sensor Evaluation Interface Board APPLICATIONS 
• Oxygen Detection
• Portable Equipment
• Breathing Apparatus
• Inerting
• Medical
• Lab Equipment
• Agriculture
• Incubation
• Fire Prevention
• Flue Gas in Condensing Boilers

LOX-EVB LuminOx Evaluation Interface Board ELECTRICAL AND ENVIRONMENTAL SPECIFICATION

Supply Voltage (Vs)	4.75-5.25 Vdc
Supply Current (Is)	<50mA
Output Types	RS232, RS485 and 0-5V
Operating Temperature	0°C to +50°C
Storage Temperature	0°C to +60°C

LOX-EVB LuminOx Evaluation Interface Board PERFORMANCE SPECIFICATION

LuminOx Sensor Compatibilit	0-25% (O2 % version) 0-300mbar (ppO2 version)
Resolution	0.01% / 0.1mbar (Digital Outputs) 0.01V (0-5V Analogue Output)

LOX-EVB LuminOx Optical Oxygen Sensor Evaluation Interface Board MECHANICAL

Connection	9 Screw terminals
PCB Dimensions	75x55mm max

The LuminOx range has been designed as an alternative to electrochemical sensors but with the benefits of RoHS compliance, long life and complete environmental compensation built-in.

The sensor is available with and without a built-in barometric pressure sensor. LuminOx’s native measurement is partial oxygen p ressure (ppO2) in mbar. By incorporating a barometric pressure sensor, LuminOx is able to measure O2 vol. % in addition to ppO2

Unlike electrochemical sensors, LuminOx requires no additional signal conditioning circuitry and connects directly to the customers microcontroller via 3.3V-level RS232 link. This reduces costs and simplifies system design.

Rain Collector Sensor - Rainfall Sensor

Rain Collector Sensor Rainfall Sensor
This self-emptying, tipping bucket style rain collector utilizes an 8" diameter openning to meet NWS specifications for statistical accuracy. Rainfall is gathered in the collecting bucket and funnels through a small openning into a tipping mechanism. When the mechanism has 1/100th of an inch of water in it, it tips.  A count is then transmitted to an indicator and the water emptys from the tipping mechanism, through the bottom of the collector bucket to the outside.

Rain Collector Sensor Rainfall Sensor
Tipping bucket, self-emptying rain collector.  8" diameter openning meets NWS specifications for size and accuracy.
Dimensions: 8.63" O.D. x 7.88" Deep
Weight: 1.77 lbs.

The rainfall collector requires no manual emptying. Each tip of the bucket is equivalent to 1/100th of an inch of rain. It utilizes a normally open circuit that is momentarily closed each time it tips.  As such, it can be connected to any simple counting circuit, including Maximum's Rainwatch indicator.

Rain Collector Sensor Rainfall Sensor Features
Outside rainfall collector meets NWS specifications for size and accuracy, and is self-emptying for your convenience.
The collector bucket can remain outdoors year-round.  Freezing weather will not damage the collector, but readings of snow or freezing rain are not to be considered accurate readings of rainfall.
Ships complete with 60', 22 AWG, 2-wire, UV protected cable.

Rain Collector Sensor Rainfall Sensor Specifications 
* Type: Tipping bucket, self-emptying
* Dimensions: 8.63" O.D. x 7.88" Deep
* Weight: 1.77 lbs.
* Cable: 60', 22 AWG, 2-wire, UV protected
* Collector Diameter: 8.00"
* Collector Height: 8.00"
* Mounting Diameter: 9.60"
* Housing Materials: ABS Plastic
* Housing Color: Dark Green or Black
* Accuracy: +/- 1% at rates of rainfall up to 1" per hour if collector is properly maintained.
* Required Maintenance: Keep the collecting area and screen free of debris (leaves, branches, etc.). Glean the tipping bucket surfaces and the external surfaces of the collector occasionally with a mild detergent.
* Counting Mechanism: Self-draining, tipping bucket design. The mechanism is factory calibrated so that it automatically tips every 0.01" when installed on a level surface. As the bucket tips a magnet passes back and forth in front of a reed switch. The reed switch is activated as the magnet passes by causing a normally open circuit to be closed momentarily. Each time the circuit is closed the digital readout counts up 0.01".
* Electrical Characteristics :
     Switched current: max 500 mA
     Switched voltage: max 200 VDC
     Contact Resistance: max 100 mOhm
     Contact Capacitance: max 0,25 pF

OXY-Flex Oxygen Analyser

The OXY-Flex Oxygen Analyser is suitable for measuring in oxygen closed systems, such as ventilation pipes and boiler exhaust flues. 

The OXY-Flex Oxygen Analyser is designed to measure the oxygen concentration in air or gas mixtures with temperatures of -100 to 400⁰C. The oxygen analyser employs a well proven, small zirconium dioxide based element at its heart and due to its innovative design does not require a reference gas. The oxygen sensor element is mounted in the tip of the stainless steel probe and is protected by a sintered stainless steel cap. The IP65 waterproof die-cast aluminium housing accommodates the electronics and provides the interface for the customer to connect to.
The OXY-Flex Oxygen Analyser uses a unique closed loop measurement system. While the sensor continuously measures the oxygen level, a heartbeat signal is also generated providing an immediate warning of any failures.
The OXY-Flex can be configured to output measuring ranges of 0-25% O₂ or 0-100% O₂. The entire measurement range is linear in both cases. The outputs can be configured to either 4-20mA and 0-10Vdc outputs or an RS232 serial communications interface.
Typical applications include; combustion control of industrial boilers, burning oil, gas, coal or biomass; incubators; composting probes and welding equipment.

Performance evaluation of ultra small volume temperature and humidity sensors HTU21D and SHT21

Performance evaluation of ultra small volume temperature and humidity sensors HTU21D and SHT21
Ultra small size of the temperature and humidity sensor with small volume, high accuracy, is widely used in mobile phone, HVAC, communications, medical, environmental monitoring, household appliances, control panels, editor recently from isweek ( http://www.isweek.com/ ) to get the market on the most commonly used HTU21 and SHT21 two of the sample product. These two kinds of products to do a detailed comparative evaluation, the evaluation focuses on the price, performance, power consumption and other aspects of analysis, for your reference.

HTU21d
1、HTU21D temperature and humidity sensor features
Humidity sensing elements made of high performance based on a new generation of HTU21D temperature and humidity sensors set new standards in size and intelligence: it embeds without pin DFN package for double row flat reflow, bottom 3x3mm, 1.1mm. height sensor output after calibration of the digital signal, the standard I2C format. The output mode of diversification the wide operating voltage range, with high accuracy and precision of temperature humidity.HTU21 series module designed for low-power small volume design, good quality, fast response speed, strong anti-interference ability, high price Dots, tiny volume (3x3mm), and extremely low power dissipation make the HTU21D the choice for all types of applications.
2、Comparison of important parameters of HTU21 and SHT21 sensors：

Module	HTU21D	SHT21
Supply Voltage	1.5-3.6V	2.1-3.6V
Humidity operating range	0-100%RH	0-100%RH
Tempertaure operating range	-40℃-125℃	-40℃-125℃
Maximum power consumption	2.7uW	3.2uW
Output	I2C	I2C
Relative Humidity Accuracy	±2%RH	±2%RH
Response Time	5S	8S

From the above comparison can be seen:
Although the HTU21D and SHT21 parameters are generally similar, but slightly HTU21D some advantages: wide supply voltage (1.5V - 3.6V), lower power consumption than the SHT21 (2.7uW), HTU21D + 2%RH with humidity accuracy is higher than SHT20 (+ 3.5%RH), equivalent to SHT21 (+ 2%RH), but the price is over SHT21 cheaper, 5S response time is faster.
3. HTU21D sensor size is as follows:
1) Sensor size：

Note: dimensions are mm, tolerance is + 0.1mm, has grounding sensor at the bottom.
2） The back electrode of the sensor and size

4、Comparison of appearance and pin aspects of HTU21D and SHT21
The appearance and size distribution and pin definition, HTU21D and SHT21 are exactly the same, can be directly implemented pin to pin replacement.
 
HTU21D                       SHT21
　　5、HTU21D and SHT21 software：
The HTU21D and SHT21 are both I2C interface digital outputs with the same timing of start and stop signals.
· Activating signal
Start the transmission, sending a data, including the DATA line in the SCK line during a high level to low level jump.

· Break alarm
The termination of transmission, stop sending data, including the DATA line in the SCK line of high level during a jump to a high level.

HTU21D and SHT21 have the same command list：
 
Both HTU21D and SHT21 are the actual use of the four pins, power supply and power supply, two port I2C communication. The output is digital quantity: 14 bit and 12 bit temperature humidity value, can also through the user registers to modify 12 temperature and 8 humidity.
Therefore, HTU21D and SHT20, fully compatible with SHT21 protocol software, can be replaced by each other.
6、HTU21D temperature and humidity sensor actual measurement effect display:
1）Using four bit temperature and humidity demonstration Demo test, and with the host computer software to implement data records:

Four bit temperature and humidity demonstrationDemo

PC recording software
As can be seen from the figure above, the consistency of the 4 HTU21D products is very good. From the graph, we can see that the recorded data curve has been flat, indicating that the HTU21D stability is good
2）Using homemade ribbon HTU21 with 1602LCD display, and high-precision handheld table data contrast
In order to facilitate customer testing, manufacturers introduced has been welded with small PCB board HTU21D PCBA:


Conclusion: HTU21D and SHT20, fully compatible with SHT21, hardware pins can achieve Pin to Pin, no need to modify the circuit board. The software program is basically the same, both can achieve a compatible replacement, do not need to make any changes. From the manufacturer's price, HTU21D SHT21 more than SHT20, the price advantage is good choice for manufacturers to reduce production cost.