Now that there is an integrated temperature transmitter, which signal is better and more stable to collect?
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To detect temperature, an integrated temperature transmitter can now be used, but its output remains: Pt100, 4~20mA, and other signals must exist for a reason, so which signal is more stable and accurate to be directly transmitted to the control room on site?
There are also many grades of integrated temperature changers. If it is a very important control point and chain point, you can use rosemount's 3144 temperature changer. Of course, the cost is very high (more expensive than differential pressure changers). If you go down a grade, you can use rosemount's 248 integrated temperature changer. Domestic integrated temperature changers are not recommended to participate in control and chaining. If it is a small system with few temperature points, just a few temperatures, and it is not important, you can use domestic integrated temperature changers, which can save temperature cards. Ordinary temperature points can be considered to be directly entered into the control system without using temperature changes.
If the distance from the site to the control room is relatively long, an integrated temperature changer is generally used, with a 4~20mA output. The main reason is that the current signal can be transmitted over long distances. Shielded wires are used, which have strong anti-interference ability and are not affected by line resistance.
The integrated temperature transmitter combines the thermocouple and compensation together, uses ordinary shielded wires for transmission, and outputs a signal of 4~20mA to the module. The two models mentioned above are really informative.
Pt100, 4~20mA or 1~5V can be used, which is the standard signal of type III meter. In fact, it is also possible to directly output the mv signal, and then use pt100 graduation sign to convert it to DCS.
The instrument does this to correspond to different DCS manufacturers. Some DCS manufacturers do not have direct PT100 access cards and need to be converted.； Some manufacturers have cards for direct access of PT100, but generally the wiring is 3-wire, so there is one more type of cable to use. By using an integrated temperature changer and a 4-20mA signal, you can remove the card that directly connects the PT100. The wiring is also done with a 2-wire shielded wire, which makes it easier to buy spare parts and maintain in the future.
The output current signal is the best. If stability is considered, it is best not to install an integrated temperature transmitter, because each additional temperature transmitter increases a fault point. From a maintenance perspective, on-site equipment should be minimized as much as possible, and the control system has Pt100.mV cards. Generally, the integrated temperature transmitter is used because the site is far away from the control room, and the current signal is suitable for remote transmission.