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I ask for confirmation of the connection of the Pt100 as indicated in the manual Mnl158b100, is it correct that the Pt100s are connected in series? Is it possible to have a 3-wire connection?
The resistance thermometers are temperature transducers, as the temperature varies they have a corresponding variation in resistance. The Pt100 are so named because a resistance of 0 Ohm corresponds to 100 degrees centigrade, while for the Pt1000 their resistance is 1000 Ohm. To detect the resistance value, a current is passed through it and the voltage drop is measured at its ends, by Ohm's law the resistance value is given by Resistance = Voltage / Current. From this it is clear that to acquire the correct resistance value it is necessary to have known the current value that passes through the resistance, which is why our analog acquisition module has an output current generator Iexc whose value is controlled by the input isense. It is therefore evident that if you wish to acquire more resistance thermometers, it is essential to connect them in series with each other so that they are all crossed by the same current value (As indicated by connection schemeTo accurately read the temperature, it is important that the current flowing through the transducer is as low as possible, high currents would heat the transducer and distort the reading. Consequently, very low currents cause a low voltage drop across the transducer and therefore the importance of acquiring the voltage value across the ends with great precision in order to have a reading resolution. Like all resistors, the Pt100 / Pt1000 also have 2 connection wires, but if there is a certain distance between the transducer (RTD) and the point where the signal is conditioned (Acquisition module), there is a risk that the resistance of the particularly long connection wires can affect that of the transducer thus distorting the readings. To compensate for the resistance of the connection line, two other wires are used connected in parallel to the connection pins of the thermoresistance (Here is the 4-wire connection diagram). Having the acquisition module a differential type input it is recommended to use a twisted cable for the two voltage reading wires at the ends of the transducer (As indicated in the diagram), in this way the effects of the disturbances induced on the cables are also limited, improving the reading.
I would add that on the market there are both 2, 3 and 4 wire heat resistances. The 3 or 4-wire resistance thermometers are nothing more than 2-wire thermoresistances to which two wires have been connected on one or both ends precisely to compensate for the resistance of the connection cable.
So it is clear that to transform 2 or 3-wire thermoresistances into 4-wire thermoresistances, just add additional wires for the connection.
I would like to know how to detect the temperature from a Pt1000 probe with SlimLine, and how one or more outputs are activated.
Just make a simple Ladder program where with the function block SysGetAnInp the Pt100 / 1000 input is acquired from a module mixed signal expansion (Maximum 2 Pt100 / 1000) or from one module analog I / O expansion (Maximum 10 Pt100 / 1000). The value returned by the function block is a REAL value which indicates the temperature in degrees centigrade, it will be sufficient to follow with logic branches where the value is compared with a reference value to activate / deactivate the desired logic outputs. I am attaching a simple test project, Press, source file.
Hello I would kindly need clarification on the connection of a single Pt100 to the module SlimLine mixed signal. I have a 100-wire Pt3 (2 red and 1 white) tell me if it is correct.
IEcx= Red thread, Ai00= Red thread Ai01= White wire and then how do I connect the other inputs?
As explained previously, to acquire the Pt100 value, a very low current generated by the board (Output on terminal IExc) is passed inside them and the voltage drop across it is acquired. Having said this, it is evident that the electrical circuit that causes the current to flow must be closed, therefore one end of the Pt100 must be brought to AGnd.
In your case we will have IExc= Red thread, Ai00= Red wire, the white wire you will have to connect it to Ai01 is Agnd. As the other acquisition channel remains free, I recommend connecting Ai02 ed Ai03 ad Agnd.
However, this type of connection does not compensate for the voltage drop between the Pt100 and the Ai01 input as the current flows through a single wire (White wire). If the distance is greater than a few meters and if you want to have a high reading accuracy, I recommend connecting two wires near the Pt100 on the white wire, one you will connect to the Ai01 input and the other to AGnd.
I would like to kindly understand what was written in the previous post, I too find myself connecting pt100 or better 100-wire RTD3 on a PCB126C130 module but from what I deduced from the connection diagram if I wanted to connect only one I would have to connect:
1st red thread to Iexc, 2nd red wire at AI00 +, 3rd white wire at AI00- and Isense, without connecting anything to Agnd , is that correct or am I missing something?
And in the case of another consecutive 100-wire pt3, how does it connect?
Another question if by hypothesis on the module in question I find myself having occupied all the inputs on side A from pt100 while on the inputs on side B I wanted to connect 2 thermocouples and 2 pt100, the connection can be made as per the "mixed acquisitions" manual, that is:
1a thermocouple on AI00 + and AI00-,
2a thermocouple on AI01 + and AI01-,
1st pt100 1st red wire on Iexc 2nd red wire on AI02 + white wire on AI02-
2nd pt100 1st red wire on AI02- 2nd red wire on AI03 + white wire on AI03- and Isense
Naturally, setting the jumpers correctly.You've described the wiring perfectly (better than I could). Unfortunately you get lost a bit between the colors of the wires and the signals, better to refer to a diagram rather than a description. But in general, the resistance thermometers must be placed in series and powered in current, which is why we exit from Iexc and closes the series on isense, this serves to guarantee a constant current in resistance thermometers.
The voltage at their ends is acquired in differential with inputs AIxx + and AIxx-, if the connection cable between the thermoresistance and the board is very long it is recommended to use a 4-wire connection (In practice, the two red wires are already connected to one end, a white thread must be added in parallel to the existing one). In this way the electrical “noise” is compensated thanks to the use of twisted cables and the resistance of the connection cables is compensated by separating the power cables from the voltage reading cables.
Remember that even just using a thermocouple input you lose the use of the xI04 + / xI04- input from the module where the thermocouple is acquired. The input is used internally for cold junction compensation. Therefore, in the case of several thermocouples, it is better to acquire them all from the same module (Side A or Side B).
I have a PCB126C130 analog expansion module with 10 pt1000 probes: if I don't connect one of them to make the others work I have to make the jumper in place of the missing probe, is there a way to avoid this?
As explained above, the circuit must always be closed between Iexc e isense, so if you remove a thermo-resistance you have to wire the series correctly, but this does not mean that you have to short-circuit the inputs of the module.
The inputs of the module remain available for any other type of acquisition.
I agree, I meant that the installer of the system in setting up the system must know that if he does not have one or more probes at the moment, he must make the jumper that he will then remove when they are reconnected.
Hi I'm trying to use modules SlimLine to control temperature and manage solar panels with differential probe and two panel sources on two pitches arranged differently.
Someone has already made a function block to activate pump and diverter valve with Pt100 or Pt1000 probes.
I don't know if it can serve you but I am attaching the FB OnOffRegulation that I have made to manage the adjustment of unit heaters in the company. The FB manages the temperature threshold with a dead band to avoid the pendulums on the command (Print, library).
In this topic find more information on a similar topic.
I have a CPU module SlimLine coupled with an expansion module for analog inputs, to which I connected a Pt1000 probe. Now I should connect an irradiation sensor, but I have to choose if its output is 0-10V or 4-20mA.
Will I have to put it in series with the probe? which one should I choose to be compatible with the acquisition of the probe?
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