Instrument grounding issue
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Experts, devices such as level gauges, pressure transmitters, or thermal resistors are all explosion-proof. When the interior wiring is exposed after opening the device, there is a grounding screw – is it necessary to connect this wire? There is also a grounding point on the outside of the enclosure. I checked the petrochemical standards and found that grounding is not required when the voltage is below 36V; then why do all instruments have such a grounding point? For safety reasons, is it possible not to ground it internally? Thank you!
This post was last edited by 275340019 on 2019-7-22 at 18:43. In explosive hazard environments, the instrument enclosure needs to be connected
The work site connection is done; is it still necessary to connect the shield wire? There seems to be some repetition in the sensory functions. I’m a beginner with instruments; please give me some guidance. Thank you!
Shield grounding is a type of working ground.
Grounding on the inside of the watch and on its case is not necessary in most cases. 1. The shield wire is grounded at one point in the control room ； 2. The case must be grounded. But it can be achieved by grounding through a lapping device. That is, as long as it is installed on metal equipment or the mounting bracket connection device is grounded, no special wiring is usually required. Note: At this point, the watch case and the wire shielding layer should be insulated from each other. 3. The enclosure only requires a dedicated grounding connection when the instrument is installed on a non-conductive device. Generally, it is done by connecting to the device’s ground wire, trying to avoid grounding through the shielding of the connection wires ； 4. Instrument circuits, signal wires, and control wires are not grounded in principle. However, in the presence of extremely strong interference, grounding near the source of interference can be considered. For example, in the case of a transmitter installed on a high-frequency heating furnace that is not functioning properly, consider trying to connect the internal ground wire to the furnace body.
If it is flameproof, internal grounding and external grounding are required, two separate circuits!
The expert has already provided a very comprehensive answer; I’ll give a brief explanation: Unless it’s in an environment where there is a high risk of fire or explosion, grounding of the enclosure and internal components of instruments rated at 24V or lower is not necessary； In explosion-proof areas, 220V instruments should be grounded; the grounding bolt on the enclosure and the internal grounding bolt are connected to each other, so either one can be used for grounding (it’s not a problem if they aren’t connected, as the instrument is connected to pipes that are already grounded) ； In locations where there is a risk of fire or explosion, the grounding bolt on the 24V instrument enclosure can be connected to ground; it can be connected to the equipment or to a separate grounding point (the grounding of the 24V instrument enclosure is not necessarily connected to the internal grounding), and the internal grounding does not need to be connected. Under no circumstances is it recommended to ground the instrument shielding wire on the instrument side; instead, it is advisable to ground the shielding layer of the instrument cables at the instrument junction box or at the DCS cabinet. The instrument cable is grounded at one end to prevent a potential difference from developing in the shielding layer, which could otherwise create feedback circuits and affect signal transmission.
Single-ended grounding is sufficient; the control room side is connected
Don’t meddle, don’t create problems; don’t connect the cable shielding to the casing of low-voltage instruments. If it’s important, say it three times. Whoever doesn’t obey – may electricity kill them, roast them to death, turn them into dried meat strips or spicy snacks.................... :P
Does the housing of a flammable toxic gas detector need to be grounded in an explosion-proof area? There is a shielded wire inside ( )