What are the terms of combustible gas detectors
"Parts Per Million" (PPM) concentration measurement unit, generally used in the field of gas detection. For example: 1PPM hydrogen sulfide in the mixed air means that there is one unit volume of hydrogen sulfide in every million unit volumes of gas.
Flammable limits are divided into Lower Explosive Level and Upper Explosive Level. The unit of LEL and UEL is usually a percentage, which refers to the percentage of a certain gas contained in air (or oxidant). In the environment below the LEL, there is too little combustible gas to burn. When the concentration of combustible gas in the environment is higher than the UEL, it will not burn due to too much gas. The LEL and UEL values of various combustible gases can be obtained in relevant materials.
Threshold Limit Values (TLV) TLV means that when the content of a certain gas in the air is less than this threshold, the health of workers who are fully and continuously exposed to the environment will not be damaged. When referring to this value, the standard promulgated by the state must prevail, and the latest correction value should be used. TVL consists of the following two parts:
TLV-TWA This value represents the time-weighted average concentration value in the environment. The vast majority of workers will have no health problems working in this environment on an 8-hour-a-day, 40-hour-a-week schedule.
TLV-STEL This parameter is defined as a 15-minute weighted average. At any time of a working day, the concentration of a certain harmful gas in the workplace must not exceed its specified threshold, even if the total weighted average of the day The average threshold is reached. The number of times that the average threshold value is exceeded and the instantaneous threshold value is lower than 4 times in a day, and the duration of each time must be less than 15 minutes.
IDLH If the worker does not wear a gas mask or is inexperienced in escaping, and the gas concentration in the working environment reaches a dangerous concentration, a 30-minute stay can cause permanent damage to the human body or impair the health of the human body (such as reduced vision).
The RS485 serial bus specifies the double-ended electrical interface form, and its standard is the double-ended line transmission signal. If one of the lines is in a logic 1 state, the other is a logic 0. Because the voltage loop is bidirectional and differential, it can suppress the common-mode interference in the transmission loop and greatly improve the communication performance.
Explosion range In the mixture of combustible gas and air, the concentration range between the lower explosion limit and the upper explosion limit of combustible gas is called the explosion range.
