I have to read a Type K thermocouple from a distance of about 25 m away from the temperature controller. I am thinking of using a PVC /20 AWG, type K, extension cable. Anyone knows if everything will be Ok? or could arise a signal losses due to the cable length which could affect the measurement?

 

25 meters is quite OK. Provided your measuring instrument is high impedance (most are now-days) you can go several hundred meters.

Roy

 

No problem, if you use compensate cables for 25 meters.

 

probably you won't have signal loses but you may have EM noise coming from outside the cable, to prevent both you can use a temperature transmiter and a shielded twisted pair cable, but you will have to configure both the controller and the transmiter to accept current signal.

Mariano Olivera
control Industrial
www.controlindustrial.com.ar

 

Compensating i.e. Thermocouple extension cables have the same metals as used in a TC junction. Hence it is just like installing a TC having 25 mtr. length and you need not worry about temp errors if the temperature to be sensed is on higher side (more than 300-400 for K type). In fact we are using around 50 mtr length of such cables at our plant and we do not experience much diff. in the readings taken at TC head and at Control panel.

Regarding indicators, now a days the digital indicators are having universal input type and it doesnot matter if you connect a TC directly or feed a mA signal (obtained by installing a temperature transmitter). Only the terminals shall be different for a mA signal and a mV signal.