Should temperature transmitters be installed centrally in the control room, or should integrated local temperature transmitters be used?
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This post was last edited by jacob451 on 2010-5-18 at 13:33. If 4-20mA is used to transmit temperature signals, should P+F or MTL safety-rated temperature transmitters be installed centrally in the control room, or should integrated temperature transmitters (such as Rosemount 248) be installed on-site? Please share your opinions
This post was last edited by jopenro on 2010-4-9 at 11:40. Integrated temperature control installation is the simplest option – it requires low investment, is easy to debug, and reduces the number of potential failure points
It depends on individual habits; it’s hard to say
Barrier-type temperature sensors are inexpensive, while integrated temperature sensors are more costly; in addition, an isolation barrier is required to access the control room. For temperature points that are far apart and require high precision, an integrated temperature sensor could be considered.
It’s better when the temperature changes are consistent, and the signals are uniform
Regarding temperature input into the DCS, if the DCS manufacturer does not provide a temperature module, or if a temperature sensor is needed to improve accuracy, it is better to choose an integrated temperature sensor. As for whether to use a safety barrier, it depends first on whether it is an explosion-proof area; if so, it is advisable to use an explosion-proof integrated temperature transmitter. In non-explosion-proof areas, a regular integrated temperature transmitter will suffice. If a safety barrier must be used, for applications such as signal distribution (one input, two outputs), an intrinsically safe primary instrument can be used, which is cheaper. In terms of price, well-known brands tend to be more expensive – for example, E+H temperature sensors cost around 1000 RMB, while integrated ones cost about 2000 RMB. Rosemount sensors are even more expensive, but they come with HART communication, which makes parameter setting much easier when there are many points to monitor. Other products without communication features can be obtained for less than 1000 RMB
If winter temperatures in the region are very low, will the integrated temperature sensor experience zero drift? Integrated temperature control is not recommended for devices operating in harsh conditions. Furthermore, in explosion-proof areas, an integrated temperature sensor requires an isolation safety barrier; in such cases, it is better to use a safety barrier with temperature sensing capabilities that is installed in the control room, thereby combining the functions of transmission and isolation in one unit. There is one downside: if noble-metal thermocouples are used, the cost of the compensation wires increases, so it is not recommended to install them in this way.
Consider the transmission distance; if it is long, use a temperature-sensitive type； If the distance is short, it can be installed in the control room.
At present, a thermal resistor combined with a safety barrier remains the economical and practical choice； It seems that using integrated temperature control is the trend, and fieldbus FCS will eventually be necessary.