RTD sensor question

[Peam]

I've bought a 9 pin on/on switch for my RTD sensors to add on to my panel, but will the added resistance in the wire I add plus the switch mess up the readings of the sensor?

 

[Maylar]

Not if you solder everything or use really secure crimps. Are they 2,3, or 4-wire sensors?

 

[Peam]

They're 3 wire.
I found some k type sensors of the same awg so I was planning to cut them back to run from the switch to pid

 

[BrunDog]

The point of 3 or 4 wire sensors is to measure out the resistance of those third/fourth wires to isolate the resistance across the RTD platinum element. So as long as you use 3 or 4 wire, and all your connections impart similar additional resistance, it's ok to add connectors, switches, and additional wires. All wires should be the same length, too.

FYI K type sensors are thermocouples. The RTDs are much more accurate.

 

[Peam]

The K type I'm using is for the wire only not the sensor. I wired it up last night but unfortunately the readings are out. I've determined it's the switch itself that's the issue, or possibly the grounding of it to the box? The reading goes way up or down when you touch the switch at all, yet along actually switching. When left alone, for the most part it was reading 10°F lower than the actual temperature. I do have another switch on hand to replace that one if needed

 

[BrunDog]

RTD amplifiers are super sensitive to resistance changes. That's the price of accuracy! Your switch regime has to induce comparable resistance to both the reading and sampling wire.

 

[Maylar]

The K type I'm using is for the wire only not the sensor. I wired it up last night but unfortunately the readings are out. I've determined it's the switch itself that's the issue, or possibly the grounding of it to the box? The reading goes way up or down when you touch the switch at all, yet along actually switching. When left alone, for the most part it was reading 10°F lower than the actual temperature. I do have another switch on hand to replace that one if needed

K type is a thermocouple wire, as mentioned. You can't use it as extension wiring. Each connection will create a thermocouple junction that will throw off the RTD's readings. Use copper wire.