[Discussion] Let’s talk about the usefulness of thermoresistors and thermocouples in installing temperature transmitters within control system cabinets
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Let’s discuss the usefulness of thermoresistors and thermocouples in installing temperature transmitters within control system cabinets I often communicate with the people in the factory, and they usually require that before the thermoresistors enter the control system cards, they be converted to 4-20mA by a temperature transmitter before being fed into the AI cards. Is it simply because 4-20mA is more stable than the Pt100 signal? Does it still have any meaning? To prevent interference with the signal of the cable running from the Pt100 to the control system cabinet, I think it would be better to use a thermal resistor equipped with a temperature transmitter on-site. It seems pointless to heat it up before entering the control system cabinet.
Since it has already been brought to the control cabinet, adding a transmitter is unnecessary; it only creates an additional point of failure.
Do we need to add a transmitter at the control cabinet as well? Only by installing the transmitter on-site can accuracy be improved (after all, wires also have internal resistance); it’s completely pointless to place the transmitter in the control room. Is the 4~20mA specific resistance signal stable? It’s impossible… There is only one possibility: this AI card does not accept direct input of Pt100 signals, so it needs to be converted into 4–20mA signals for input. But with technology being so advanced these days, safety barriers can even be used as transmitters – so why is heating still necessary? What to do if the thread end comes off? What to do if you’re bitten by a rat? What to do if you get stepped on? It’s so messy; what should I do if I remove something by mistake during maintenance? I don’t understand at all……
1. Increase detection errors. 2. Improve lightning protection performance. 3. Standardize the card components. 4. Increase investment, which is beneficial for some people. 5. Expand the floor space required by the equipment. 6. Raise power consumption. 7. Increase heat generation within the cabinet area. 8. Slightly increase the complexity of maintenance tasks. 9. Some people prefer such an increase
This post was last edited by jlszhoujidai on 2016-6-28 at 15:57. I agree with the comment above: unless the site conditions are poor and make it unsuitable to install temperature sensors, they should be installed on-site as much as possible...
Check what signal type is used for the input of the card being ordered; some people opt for 4-20mA input cards due to cost considerations or ease of maintenance. In such cases, a temperature sensor is still required
The estimation module does not support thermistor signals; it can only convert to 4-20mA
It depends on the situation. In the case of older factories, temperature control is usually installed in the cabinet room. If the location is in an explosion-proof area, it is also beneficial to place the temperature sensor inside the cabinet. Sparks can be generated when the components are powered on, and it is very dangerous if the temperature control measures do not meet the explosion-proof requirements. Additionally, the natural environment plays a role as well; if the area experiences extremely high or low temperatures, placing the temperature sensor in that location can lead to errors, whereas the temperature inside the cabinet remains more constant. Some poorly manufactured temperature sensors are affected by ambient temperature, which can lead to errors or prevent them from functioning properly in extreme conditions; in such cases, these sensors should be placed inside a cabinet. In the northern regions, the lowest winter temperatures can drop below minus 30 degrees, while peak temperatures can reach around 40 degrees. Such conditions require high precision in terms of temperature control; if the device is placed inside a cabinet, the error margin will be relatively smaller. The above are my personal views; please don’t take them too seriously.
1. It is generally installed nearby; otherwise, wire resistance will affect the results； 2. Modules that support RT100 should be more expensive than ordinary analog input modules, right? ；
Does DCS need to acquire its analog curve view? It seems that in our unit, we go straight to the platinum resistors in the PLC control cabinet, with transmitters added as well