Measuring water level in a tank

Using copper cable from a junction box to the card instead of TC cables it in effect produces a second thermocouple at the terminals (dis- similar metals).
This even happens when the TC cable is run directly to the card as the print/internal wires to the components is usually copper that is why there is a compensation RTD normally fitted at the card.
Mas01 has proved this by wiring the RTD compensation terminals through to the junction box and moving the RTD cold Junction compensator to the box, this has removed the error he was getting.
The pic shows the typical advantages/disadvantages, there is also a cost parameter. However, As far as I'm aware the temperatures he is measuring do not appear to be critical (well the ones he is adding) so not a problem but in saying that, this is a test rig for something that cannot be shown due to company policy so it is more than likely that there could be that the many other sensors are used for critical measurement, As I said before, I have seen some of the code and it is my impression that this rig has been designed with cost in mind rather than accuracy there are some fudges that have been implemented that I find a little disturbing and poor programming, in saying that this rig has been upgraded by a later version of PLC and perhaps may be not by the original designer.