Hi guys

i am having some trouble with a PT100 link to sensor is http://ie.rs-online.com/web/p/plati...43D3439392D39333730267374613D3439393933373026

and it is being controlled by this controller http://ie.rs-online.com/web/p/pid-temperature-controllers/6119879/

The probe is only a week old and was working fine for the last week until power was turned off on the tank where the probe is for a day and when power was turned back on the controller is now constantly reading a flashing FFF which, according to the controller manual states that there is a burnout after occurring on the sensor. i have disconnected the cables (4 wires two wires each clamped under 2 terminals) and measured the resistance across the terminals and i am getting 111 ohms. Does this mean the probe has failed as i am not so sure, and if so i can only assume that there is some sort of spike on the line when the power was turned off and on again? But i can only guess this. The controller itself is also only new. Any advice would be muh appreciated.

 

Check the controller's input source function settings. If they are not set to the wrong type of input then
change sensors and see if the problem goes away. If not change controllers and test again.

 

...i have disconnected the cables (4 wires two wires each clamped under 2 terminals) and measured the resistance across the terminals and i am getting 111 ohms. Does this mean the probe has failed ...?

That value is very nearly what you would expect to see. So my guess is that the probe is fine and the problem is at the controller. Note that you can simulate the probe by substituting a fixed resistor in the 100-150Ω range. But again, it sounds to me like your probe is fine.

 

... the controller is now constantly reading a flashing FFF which, according to the controller manual states that there is a burnout after occurring on the sensor....

The manual says other things can also cause the flashing FFF. I think improper settings could cause it. You may just need to reprogram your controller.

 

Thanks Wayneh I agree with the probe being correct for when I put it in a tub of hot water the reading on multimeter went up to 125 ohms so it is registering. As far the controller goes I didn't know there was programming involved I thought it was a matter of setting the setpoint and that was it. I don't see how I can reprogramme it as the buttons on the display wI'll allow me to change the set point but that's all

 

Hello,

There are a couple of switches inside the controller.
See the attached datasheet for more info.

Bertus

 

Yeah I see that alright just don't know why I'd have to adjust them now all of a sudden after it working ok for almost a week