DLUN,
At the risk of not knowing what application you are using for monitoring the 30 thermocouples, or why it is important to check them every second, I would like to add my 1 1/2 cents worth.
As you probably know, thermocouples are subject to what is known as "thermal inertia" meaning it takes time for the thermocouple to react to a change in temperature. Especially when a thermocouple is cooling down. Heat goes to cold. Whether cold is room temperature, or any other reference point, it dictates how fast a thermocouple reacts to a cooling change, as opposed to a heating change. I.E. it takes longer for a thermocouple to cool, because the change to warmer takes energy, whereas the cooling process takes no energy. Cold can be defined as an infinite heat sink (Earth, Factory, test environ or Space) and heat as a localized event, in terms of a Delta T, ambient vs. desired process variable (fish sticks cook better at 400 F than at ambient) in respect to the limitations, (Earth, Factory, test environ or Space).
To add to the equation, the distance of the heating (or cooling)
body or element, from the thermocouple's aspect, is inversely proportional to the square of the distance from said body or element. The placement and location of the thermocouple needs to be taken into consideration when evaluating raw data.
In short, it may be beneficial to extend the sample times, of the thermocouples, to 2 1/2 to 5 seconds. It might result in a more representive temperature change during the measured process and it will make the asssociated PID loops ( if used) easier to manage. And, it will reduce the load on the communication network (RS-485).
I hope I have not wasted anybody's time reading this......
Dave