The wired gas alarm. Host is the front-end detection equipment switching signals directly connected to the host defense zone thus triggering the alarm host alarm, and these switching signals must be connected to the gas alarm host through two cables to the defense zone port, each wired gas detector needs to be connected to the signal line to the split-line host.
His structure is simple, the number of zones is relatively small, that is to say, there are as many gas detectors (zones) on how many pairs of cables are needed.
And the bus system alarm host is different, it is the front-end detector first switching signals connected to the address module (or called alarm module, defense zone expansion module) bus, when the detection equipment in a defense zone found that someone illegally entered, the detector sends out an alarm signal, by the address module (or called alarm module, defense zone expansion module) through the data bus to the alarm host.
Real-time alarm signals in this preventive area, the type of alarm is displayed to the alarm host keyboard, and triggers sound and light alarms, so that operators can timely and accurately grasp the alarm, timely mobilization of security personnel to deal with. The structure is more complex, but can accommodate a greater number of defense zones.
In this case, there is no need for a pair of gas detectors and then pull a pair of signal lines to the host, as long as the address module will be connected to the address module to the host of the distance can be up to 1,200 meters, and a pair of signal bus can be received up to 248 address module (or called alarm module, zone expansion module), the address module can be connected to the 8 defense zone.
If you have a larger number of defense zones, more defense zones, more complex, or a bus system gas alarm host
Expanded information:
Combustible Selection of standard gas for gas alarm calibration:
Combustible gas detection alarms are used in different environments, and the types of combustible gases detected are different. The alarm should be calibrated by selecting a suitable standard gas to ensure the accuracy of the transmission of the value, generally according to the following principles for the selection of standard gases:
(1) Select the same type of gas detected with the alarm standard gases, such as methane, hydrogen, propane and so on.
(2) Select the most important gas component of the gas measured by the alarm as the standard gas. There are working environments where there are multiple combustible gases, and the alarm detects combustible gas mixtures.
The catalytic combustion type alarm detects not the concentration of a gas, but all combustible gases in contact with oxygen in the air oxidation reaction, in the specific verification work does not have to match all the standard gases in the measured gas mixture, just choose the environment of the most important one of the gas components as the standard gas.
(3) the use of alternative gases for verification.
The catalytic combustion type alarm determines the gas concentration by detecting the heat of combustion of the combustible gas. Although the lower explosive limit of various gases are not the same, but the concentration of the gas and the heat of combustion of the gas there is a corresponding relationship between the lower explosive limit of most combustible gases concentration and its heat of combustion of the product approximately equivalent to the same constant, generally between 1050 ~ 1100, then the limit of the heat of combustion as a standard.
In the use of catalytic combustion-type alarms to measure the lower explosive limit concentration of most combustible gases are approximately equal to the lower explosive limit of the concentration of isobutane, so that isobutane can be used as a standard gas to calibrate the majority of catalytic combustion-type combustible gas alarms. But for a few combustible gases, such as hydrogen, carbon monoxide, hydrogen sulfide and so on.
Since the heat of combustion and the product of the lower explosive limit concentration and isobutane is a big difference, the calibration should use the same standard gas of these gases, and can not be replaced by isobutane.
(4) the use of alarm instructions given in the calibration gas, with calibration coefficients or correction curve to use.
Because of the different manufacturers of alarms, different production processes, the type of catalyst used in the sensor and the amount of difference, the same concentration of the same gas in the different manufacturers of the alarm sensor bridge on the heat of combustion will also be different.
This situation some production will be given in the manual with different gas calibration calibration coefficients or correction curve, with the standard value of the standard gas multiplied by the calibration coefficient that is the standard value of the measured alarm.
(5) The oxygen content in the standard gas must not be too low.
The catalytic combustion sensor needs oxygen to participate in the reaction, at least 8% of oxygen can be measured accurately, the oxygen content of the air is 20.9%, the standard gas used must be air as the gas, if you use nitrogen as the gas, the instrument can not correctly display the value