TC90x maximun sensors wire lenght

[afecomt]

Good day

we are facing problems with TC903 thermostat (16 units) using a remote probes RS-03.

The TC903 were installed on a central electrical rack, and probes are distributed along the facility. The probes are about 50-100 m  away form the TC903 location.

The ambient temp.  varied so fast. 1 time per second, from  low to high values. please see the video.

We semi-solved  the issue earthing one end of the shield of the cable. Now temperature varies 0.5 ºc each minute. not as stable as desired but acceptable.

The width of the cables is 1,5 mm2, shielded.

Our question is: how long is the maximun of the cables to connect the sensor?

thanks in advance.