Issues with the range of PT100 thermistors
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I suddenly thought about a question: the measurement ranges for temperature points on the DCS are different, but all the sensors in the field are thermal resistors. Logically, thermal resistors with different measurement ranges should give the same resistance value at the same temperature, so what is the purpose of setting these measurement ranges? 2. Once the temperature exceeded the measurement range and could not be displayed, I increased the measurement range of the DCS, and then it was possible to show the values outside the original range, with accurate readings. 3. So I think the measurement ranges set for this DCS are meaningless; perhaps they should all be standardized to one single measurement range. 4. Or, just like with the flow measurement range, if accuracy can be ensured within that range, in some cases it is still possible to make measurements outside that range, but accuracy cannot be guaranteed. Have you ever wondered whether PT100 sensors with different measurement ranges can be used interchangeably on-site?
Regardless of the measurement range, Pt100 remains the same. A small measurement range can improve display accuracy.
If the resistance signal goes directly to the DCS’s resistance card, it makes no sense to set a measurement range； If the resistance is converted into a current (or voltage) signal through a safety barrier (or distributor) and fed into the current (or voltage) input card of the DCS, it is necessary to set the measurement range.
1. A smaller range results in a larger interval for the current values, which leads to smaller fluctuation errors. Currently
The PT100 output is originally an RTD signal; it is only when a transmitter is used that a 4-20mA signal is generated. The RTD output has no specific range
Similarly, on our end we use the 316 resistor card from DCS Zhejiang University Control System; therefore I don’t think it makes any sense to set a measurement range. I’m still a bit confused about why there is a measurement range option when selecting a thermometer – what’s the purpose of that?
Entering the IO card directly without going through a safety barrier or a temperature transmitter
As long as the PT100 lengths are the same, they can be interchanged; the calculations remain the same, and it only outputs the RTD signal