Technical characteristics of combustible gas detector Introduction
Combustible gas detector is an instrument used to detect the concentration of combustible gas, which is widely used in petroleum, chemical industry, coal mine and other industries. The use of flammable gas detectors can effectively ensure the safety of staff and avoid fire and explosion accidents caused by flammable gas leakage. So what are the technical characteristics of combustible gas detectors?
Technical characteristics of combustible gas detector:
Interference-free packaging:
The detector is encapsulated in an explosion-proof metal casing. A cover with glass is screwed onto the case. A magnetic programming button located on the transmitter faceplate allows it to be operated with a hand-held magnetic programming tool, allowing for non-intrusive operation of the sensor interface. All calibration and on-site debugging can be carried out without opening the cover and keeping the original state on site.
Easy Calibration:
Calibration prompts are displayed on the LCD display with backlight, which greatly simplifies the calibration steps. A technician can simply start the calibration procedure with a magnetic programming tool. Once the calibration procedure is started, the detector will display the calibration menu, which provides two choices of zero calibration and initial calibration. Select ZERO to start the automatic zero function. When calibration is complete the display will return to the calibration menu. Selecting SPAN will start the automatic initial state calibration, and the display screen will ask for the gas and its concentration that the detector is set to. As soon as gas is supplied, the detector begins an automatic initial calibration. When the signal stabilizes, the detector will record the initial data and prompt the operator to disconnect the gas source. Once the gas concentration returns to zero, the detector will automatically resume its normal operation. If for any reason the detector is unable to perform the calibration procedure, the detector will display an error message. The procedure takes less than three minutes and is virtually error-free.
Signal output:
The infrared gas sensor has two signal outputs: analog 4~20mA output and RS-485 data bus output. The 500 type only has a 4~20mA output. The output signal is a 4~20mA linear analog signal related to the detection range. This signal is compatible with Series 10 and Series 12 multi-module controllers, programmable logic controllers, and other standard data acquisition devices. The analog output has two other functions. One, when entering the calibration menu, the 4~20mA signal will drop to 2mA. This low current is maintained until the sensor returns to normal operation. Second, once an error occurs, the 4~20mA signal will drop to 0mA, and this situation will remain until the error state returns to normal. Changes in these output signals can be used by external equipment to identify and record the working status of the sensor.
RS-485 data communication uses Modbus RTU protocol, which is compatible with almost all programmable logic controllers, man-machine interface software and other control systems. Because the Modbus RTU protocol is a standard. The following information is available from the RS-485 communication interface: detector readings, detector alarm points, calibration mode, detector errors, status of both alarms, and calibration procedure errors. The address of RS-485 can be changed by the dual in-line package switch. Communication is two-wire, half-duplex, with a detector as its servo. Theoretically, the main controller can simultaneously control 256 different detectors at a distance of 4000 feet.
Alert Features:
The infrared gas detector has three relays, two for alarm and one for fault self-test. There is no relay. These three alarms can be adjusted to the following working states through jumpers: contact state (normally open or normally closed can be selected), and the relay can also be adjusted to be continuously energized or continuously de-energized. In addition, the siren can also be adjusted to a silent state. The alarm point can be adjusted through the menu. The self-test alarm can also be muted through the menu and responds to the following conditions: zero drift below -10 percent of the measurement range, microprocessor error, infrared light source error, signal parameter error or any other obstacle to normal operation The status of the calibration. The relay contacts are rated at 5 amps at 250 VAC; 5 amps at 30 VAC.
Programming status:
The programming status function enables the user to use the magnetic programming tool to set the sensor's alarm point, RS~485 identification number, detection gas and measurement range in the menu "VIEW PROGRAMMING STATUS". Once in the program, the display will automatically flip through all the commissioning steps. When finished, the sensor returns to normal operation.
Over range:
When the gas concentration measured by the detector exceeds 100LEL of the measuring range, the display will flash and show a higher value. When the gas concentration returns to the measurement range, the display will return to the normal working state.
