Expert Answer: How to connect to HART devices MCS-XV
The new MCS-XV from Presys has three versions.
The NH version is the most basic of the three. It does not come with HART communication.
However, the CH version does comes with HART Calibrator. In the CH version, you have limited access for HART communication. For example, you have the basic and universal commands for HART such as zero, span, trim mA, etc. This will allow you to adjust the range of the instrument, monitor primary variable, adjust the current and so on.
The last and most complete version is the FH. This version comes with the Device Description (DD) library from the FieldComm group. Which means it can basically work as a handheld. Simply set specific parameters of each of your instruments and you are good to go!
The MCS-XV has an internal 250 Ohms resistance built-in. You can choose to enable it or not. With this, we have also three connection options. The mA input + HART using the internal power supply (TPS), mA input + HART using an external power supply, or also the HART ONLY option. Let’s see how we can connect in each one of these options.
mA INPUT + HART with TPS
In this set up we are going to use the option to have the transmitter powered by the calibrator itself (TPS). In this connection, you will need to connect the negative terminal of the transmitter to the mA HART input on the MCS-XV. The positive terminal of the transmitter should be connected to the TPS (+) input of the calibrator. And for the power supply, you will need a jumper that connects the TPS (-) input from the calibrator to the GND. You can check it out on the diagram below. Remember that if you choose to disable the internal resistor you will need an external resistor of at least 150 Ohms in series with the mA HART input.
mA INPUT + HART with External Power Supply
If you choose to use an external power supply, you will have to change up the connection a little bit. The negative terminal of the transmitter still connects to the mA HART input. However, instead of connecting the positive terminal to the TPS (+) input, you should connect it to the positive terminal of the power supply. Now forget about the jumper! Since you have an external power supply, connect the negative terminal of it to the GND input in the MCS-XV. Again, this is considering the internal resistance enabled. If you choose to disable it remember to use an external one. Below you can check the connection diagram.
ONLY HART (Including Network)
In this connection before you connect the calibrator to the transmitter it is important to make sure that the mA Input is NOT selected in the MCS-XV. Instead, you can choose CH-1 Input or none.
In this mode, you won’t have the internal resistor. Therefore you must have an external resistor of at least 250 Ohms in series with the power source and the transmitter. The connection is pretty straight forward from here. First, connect the positive terminal of the power supply to the positive of the transmitter as well as the mA HART input in the calibrator. In series with the resistor, connect the negative from the power supply to the negative of the transmitter. In the same fashion connect the negative from the power supply to the GND input of the MCS-XV.