“Parts Per Million”(PPM) gas detectorConcentration measurement unit, usually used in the field of gas inspection. For example, 1 PPM of hydrogen sulfide in mixed air means one unit volume of hydrogen sulfide per million unit volume of gas. Flammable limits
PPM
It is 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 gas that is present in the air (or oxidizer). When the concentration of flammable gas in the environment is higher than UEL, it will not be incinerated due to too much gas. The LEL and UEL values of various flammable gases can be obtained from the relevant guesses. Threshold Limit Values (TLV)
LEL
TLV indicates that when the amount of a gas in the air is less than this threshold, the health of workers who are abundant and continue to be exposed to that environment is not harmed. When referring to this value, it is necessary to refer to the specifications published by the state, and the latest correction value should be selected. TVL consists of the following two parts: Uniformity Threshold (TLV-TWA)
This value indicates the time-weighted uniform concentration value in the environment. The vast majority of workers work in this environment on an 8-hour, 40-hour weekly basis without any health concerns. Instantaneous Threshold (TLV-STEL)
This parameter is defined as a weighted uniform value for 15 minutes, and the concentration of a hazardous gas must not exceed its specified threshold at any time of the working day, even if the total weighted uniformity value reaches the uniformity threshold during the day. The number of times the daily edge exceeds the uniform threshold and falls below the instantaneous threshold shall not be more than 4 times, and each continuation moment must be less than 15 minutes. Concentration of Risk (IDLH)
If workers are not wearing gas masks or lack escape experience, and the concentration of gases in the working environment reaches dangerous concentrations, then a 30-minute stay can cause permanent harm to the human body or impair the health of the human body (e.g., reduced vision). RS485 serial bus
The two-ended electrical interface method is regulated, and its specification is to transmit signals with double-ended wires. If one line is logical 1, the other is logical 0. Because the voltage loop is bidirectionally differentiated, it can suppress the common mode disturbance in the transmission loop and greatly improve the communication function. Explosion Range
flammable gasIn a mixture with air,flammable gasThe concentration scale between the lower blasting limit and the upper blasting limit is called the blast scale. Township gas
It usually contains natural gas, liquefied petroleum gas, and artificial gas.
Under experimental conditions, the moment from the time the inspector touches the gas to the time when the stability indicator is reached. Normally, the moment when the stable value reaches 90% is read as the echo moment.