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Gas detectors are widely used in petrochemical, environmental protection, gasoline, coal mining and other industries. For all kinds of different safety production occasions and testing requirements, the selection of a suitable gas detector must be very important for every person engaged in safety and health work.
First of all, confirm the type and concentration range of the gas to be tested. The type of gas encountered in each production department is different. All possible situations should be considered when selecting a gas detector.
Then, choose differet types of gas detector based on industrial environment - fixed gas detector and portable gas detector.

For some Microcontrollers, the resistance of sensor connected must be less than 10kΩ when carrying out the A/D transformation. For example, the resistance of Analog Devices's analog acceleration sensor is 32kΩ. It can’t work normally on the PIC and AVR control board. So it’s suggested to read the controller manual carefully before purchasing the sensor, so as to ensure that the sensor can work normally.

The load cell has a certain overload capacity, but it shall still be prevented from overloading in installation. It should be notified that even a short-term overload can still cause permanent damage to the sensor. During the installation, a pad with the same height of the sensor could be firstly used instead if necessary, then replace the pad with the sensor. In normal operation, the sensor should generally be equipped with mechanical structure for overload protection. If the sensor is fixed with screws, the screw should have a certain fastening torque and screwing thread depth. Generally, high strength screws should be used.

Measurement method of a safety relay's DC resistance with a digital multiemter is similar to that with a pointer multimeter. According to the nominal DC resistance of safety relay, place the multimeter in an appropriate resistor and connect two test pens to the leading wire of the relay coil, then measure the resistance. Comparing the measurement result with the nominal resistance, if the error is within ±l0%, it's normal. If the resistance is obviously smaller, partial short-circuit fault exists in the coil; If the resistance is zero, the coil is short circuited; If the multiemter shows "1", the coil breaks.

Measure coil resistance, resistance of a power relay coil can be measured with the R×10Ω band, thus judging whether the coil has open circuit. Measure actuation voltage and actuation current, with an adjustable stabilized voltage supply and ammeter, the power relay can be input with a voltage while the ammeter can be connected in series to monitor. Slowly increase the power supply. Voltage and record the actuation voltage and actuation current when the power relay is attracted. For accuracy, more operations can be repeated to get the average value. Measure release voltage and release current, connect wires as the test above. When the power relay is attracted, reduce the power supply voltage slowly and record the voltage and current as hearing the relay to release again. More operations can be repeated to get the average value.

Oil leakage is a common problem for gear motor, and the problem may be caused by box quality, lubricating oil quality, oil seal quality and air pressure outside and inside the box. Meanwhile, excessive lubricating oil will also lead to oil leakage. Once the oil leakage occurs in the gear motor, corresponding measures should be taken, and this paper ATO will introduce the solutions for stopping gear motor oil leakage.

Gear motor is widely used in the metallurgy, mine, light industry, chemical industry, steel industry, cement, printing, sugaring, food industry, construction, lifting transportation and fan industry. Working environment of these industry may be damp, and damp environment will directly affect the operation of gear motor. How to keep your gear motor dry when works in such a damp environment?

The infrared thermometer is used for measuring the surface temperature of the object. ATO infrared thermometer is non-contact, handheld and easy to operate, especially suitable for measuring the temperature of various hot, hazardous or hard-to-reach objects. This infrared thermometer consists of Optics, temperature sensors, signal amplifier, processing circuit and LCD display. The Optics collects the infrared energy emitted by the object and focus it to the sensor. Then the sensor transforms the energy into an electricity signal. The signal will be turned into a digital number shown on the LCD after the signal amplifier and processing circuit.

Voltage stabilizer is a kind of power supply equipment which can automatically adjust the output voltage. Its function is to stabilize the power supply voltage which fluctuates greatly and cannot reach the requirement of electrical equipment within its set value range, so that various circuits or electrical equipment can work normally under rated working voltage. With the increasing number of household electrical equipment, the use of voltage stabilizer is more and more extensive. Domestic voltage stabilizer is mainly used to stabilize the voltage of TV, refrigerator, air conditioner, etc. Next, ATO will show you how to install a voltage stabilizer for home.

Load cell is based on the principle that resistance changes when the resistance strain gauge pasting on the surface of elastomer is forced deformation. Load cell converts the change of resistance to mV signal so as to complete the process of converting external force into electrical signal. According to its principle and structure, the fault of strain gauge load cell is often caused by some human or natural factors.

Connect the positive and negative electrode of a 1.5～3V battery with the primary coil L1 and L2 of the transformer respectively, connect the transformer’s secondary side K1, K2 respectively with the positive and negative electrode of a milliammeter. After the loop is well connected, the indicator of milliammeter turns clockwise while connecting K, and turns anticlockwise while disconnecting K, that means the transformer's terminal connecting with the positive electrode of the battery has the same polarity with the terminal connecting with the positive end of the milliammeter, namely L1 and K1 have a same polarity and the transformer is a subtractive polarity. If the indicator turns conversely to the above, the transformer is an additive polarity.

Cause of current transformer burning up

•  Secondary open circuit of the current transformer produces high voltage to burn out the current transformer.
• Long-term use of the current transformer makes the insulation aging, local breakdown or discharge occurs and overvoltage is thereof produced, thus burning out the current transformer.
• The aluminum contact surface of current transformer’s primary connection is seriously oxidized, which results in large contact resistance. The contact resistance gives out heats and burns out the current transformer
• Long-term overload operation makes the current transformer to give out heat, it is thereof burned out.

The vibration frequency of body is not in line with that of grading ring. Owing to the damping of transformer oil, grading ring has a low vibration frequency. And owing to single point welding and aluminum sheet welding, it has a poor mechanical strength. In the long-term operation, the vibration brought by the inconsistent vibration frequency of earth tag of line reactor (aluminum, welding) and grading ring causes metal fatigue and cracks. Solution: fix ascending flange base and body to reduce free-running vibration.

Displacement sensor, also called linear sensor, is a linear unit sensing metal. The function of sensor is to transform the tested physical quantity into electric quantity. The working principle of straight line displacement sensor is same as that of slide rheostat. It is used as voltage divider to present the actual position of tested position through relative output voltage. There are a few requirements for the work at the position:

Oil replacement and drying treatment of electric reactor: if the long idle time or operation time or other nature and human factors cause insulation deterioration of line reactor, water inflow or oil deterioration, oil replacement and drying treatment should be conducted to line reactor. Oil replacement of line reactor: lift the body of line reactor out, drain sump oil, wash oil tank, and wash the greasy dirt on the body of electric reactor if any. After drying, fill electric reactor with oil and replace all grease-proof rubber seals. Theline reactor can be operated only after passing the test.
Drying treatment of line reactor: its body has many drying methods. Users can adopt zero phase sequence drying method, eddy drying method, short circuit drying method and oven drying method when they dry line reactor by themselves.

Contact system maintenance

• Check whether the position of the movable and static contact points is aligned, whether the three-phase is closed at the same time; Adjust the contact spring in case of any problem.
• Check the wear degree of contact points, the wearing depth shall not be more than 1mm. In case of contact burning or welding falling, please replace timely; Slight burning will not affect the application. The sand paper can not be used to clean the contact, a shaping file is suitable.
• The resistance shall not be less than 10MΩ when measuring the interphase insulation resistance;
• Check whether the auxiliary contact acts flexibly, the contact travel should comply with the specified value. Check whether the contact is loosening, maintain or replace timely in case of any problem.

Gas flow sensor is mainly composed of a housing, a front guide frame, an impeller, a rear guide frame, a tightening ring and a magnetoelectric induction transducer with an amplifier. The new generation of high precision and high reliability gas flow sensor is designed in accordance with the advanced technology at home and abroad, and is independently developed based on the theories of gas dynamics, fluid mechanics and electromagnetics. It has excellent performance for low pressure and high pressure measurement, multiple signal output and low sensitivity to fluid disturbance, and has been widely used in the measurement of natural gas, coal gas, liquefied petroleum gas and light hydrocarbon gas.

Helical slit flexible coupling
Helical slit flexible couplings are usually called as integrated slit cutting coupling or flexible coupling, they often have good performance and cost economy, and are regarded as preferred products in many applications.
The integrated design of a complete aluminum alloy bar makes it to have advantages of zero backlash drive moment and no maintenance. The helical slit flexible couplings can be broadly divided into two basic series: single head helix slit and multi head helix slit. It has large flexibility but low additional bearing load. Such a slit design is particularly suitable for handling the angular deviation and axial deviation, but not suitable for parallel displacement deviation, because the single head helix slit would produce multiple directional bending when handling parallel deviation, which may result in the excessive stress concentration and earlier damage of the parts.
Multi head helix slit coupling reduces the slit length without losing the ability to rectify deviation, the multi head helix slits are intertwined to enhance the torsional rigidity of the coupling, thus ensuring that the coupling can still withstand considerable torque when it has great rectifying capability. This performance makes it suitable for light load applications, such as the connection between the servo motor and the screw. However, such a design also has its shortcomings. The additional bearing load will increase as the size increases. But in most cases, as the installation error is smaller, the bending moment is also very small, thus ensuring low additional bearing load.

After connecting the wires accurately according to the wiring diagram and powering on, the meter displays the thermocouple graduation firstly and then the range, measure the nixie tube on the lower part of the meter to display the setting temperature, and measure the nixie tube on the upper part of the meter to display the measuring temperature. If the upper nixie tube doesn’t display the temperature of the heating body but the other states such as “OVER”, “0000” or “000”, meaning that the output part of the meter goes wrong, following inspections shall be made:
Remove the thermocouple from the thermocouple output end of the instrument and then short circuit the thermocouple output end of the instrument with a wire. If the temperature showed on the upper nixie tube is close to the room temperature after powering on, meaning that exterior wire connection of the thermocouple disconnects, replace with a same thermocouple. If it keeps a same state as previous, meaning that the output end of the instrument is damaged in transportation, change an instrument please.

When a new system is used for the first time or the meter, sensor is replaced, calibration must be made before use.
There are two kinds of calibration in general, one is the physical calibration (in this mode, two points needs to be calibrated, namely the zero position and the range), and another is the digital calibration.

Physical calibration is applicable for most weighing systems, and digital calibration is used in the fields when the physical demarcation can't be used. However, digital calibration can't eliminate the errors, its accuracy is related with the sensor’s sensitivity, range and wiring system (four-wire or six-wire), the division value or maximum range setting, as well as the signal loss on the junction box and cable.
The scale division and maximum range shall be set before calibration.
Before calibration, the instrument shall be powered on for at least 15 minutes until the sensors and meters reach the thermal equilibrium state.