On-site wiring of bus-type gas detectors
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This post was last edited by wx_Wang81529 on 2024-7-9 at 14:29. Everyone, how are bus-type gas sensors installed in the field? Is one bus cable run to the site, a junction box is installed there, and then the probes are connected from that junction box? If no intermediate junction box is used and the wires are connected in parallel directly from inside the probe, isn’t that too unconventional? Moreover, it means that two four-core wires (four wires in total) have to be used at one electrical interface – is that even possible? Since one electrical interface is already occupied by the audible and visual alarm device, the two four-core wires can only be used through another electrical interface. How do people install fieldbus-based gas probes in practice?
Yes, when installing bus-type gas probes, they are usually connected to the site via a bus cable from the control room or monitoring center. One or more junction boxes are usually installed at the site; these junction boxes serve as nodes to connect the various probes. The power and signal wires for each probe converge in these junction boxes, from where the data is sent back to the Zhongye system via a bus system. It is very important to ensure that all wiring complies with relevant safety standards and technical specifications. .
Normally, it involves pulling multi-core cables to the on-site junction box and then splitting them out one by one for each meter. It’s definitely not possible to have one electrical interface split into two two-wire connections as you mentioned. Also, don’t you have an indoor controller? How do you set up this parallel connection?
This post was last edited by hanhaigang128 on 2024-7-9 at 17:49. The 4-wire cable of the gas sensor (2 wires for power supply and 2 wires for 485 communication) can be directly connected to the terminal blocks in the control cabinet located in the cabinet room for point-to-point 485 wiring; alternatively, an intermediate junction box can be installed on-site, with the terminal blocks of that box being used for such point-to-point 485 wiring. As for the audible and visual alarms, some of them are powered directly via plugs connected to the sensor’s circuit board (no additional power cable is needed). In cases where the audible and visual alarms are connected to the normally open relay output contacts of the circuit board, the 24VDC+ terminal of the 2-wire power supply cable from the gas sensor should be connected to the NO terminal of those relay contacts, while the COM terminal of the relay contacts should be connected to the red wire (+) of the audible and visual alarm, or to either the blue or green wire (-) of the same alarm, and then connected to the 24VDC- terminal of the power supply.
A 1-to-2 splitter can be used; the 4-core cable goes into this splitter, with one branch leading to the nearest gas sensor and the other branch leading to the next gas sensor. At that next gas sensor, another splitter is used to divide the cable further.
We used to connect the wires through junction boxes. There is a problem with installing junction boxes on-site: there are specific requirements regarding the length of the cables that run from the bus system to each point; if the cables are too long, faults occur frequently
Are you sure? The bus I understand to be is a communication bus. All probes are connected in series to the communication line, and data is read via addresses. This requires the probe transmitter to support some communication protocol for the bus. Or moudbus or FF, etc.