Splicing Thermocouple to PID and Phidget

#1: Post by **coolio** » April 23rd, 2019, 11:58 am

Hi All,

I'm currently using this thermocouple for BT:

https://www.amazon.com/gp/product/B008M ... UTF8&psc=1

It's connected to my PID, but I would also like to splice the wire and run another wire to my Phidget 1048 so that I can run Aritsan. Is there a way to do this without compromising the data quality to the 2 destinations?

Thanks!
Mark

#2: Post by **baldheadracing** » April 23rd, 2019, 1:09 pm

Short answer: no.
Longer answer: get a probe with two thermocouples inside it.
Even longer answer: I know that what you want to do works with an Amprobe TMD-56, but I don't know what protective/isolation/filtering circuitry the Amprobe has inside it. I do know the protection circuitry is pretty robust, as I've mistakenly zapped the Amprobe with line voltage with no ill effects. (The 1048 did not survive, LoL.)

#3: Post by **ballpencil** » April 23rd, 2019, 5:09 pm

I am doing exactly that, using one probe for both my PID (Autonics TX4S) and datalogger (Center 301). Just do it, both PID and datalogger device are usually high impedance inputs so they won't present a significant load to the probe, even if paraleled. Just remember to use same wire type for splicing (chromel-alumel for K-type thermocouple probes).

April 23rd, 2019, 7:25 pm

Should I just cutoff the end of the wire and use it to run to both devices? Also, what's the best way to connect the new sections?

Thanks!

April 23rd, 2019, 8:34 pm

Again...NO. You cannot use a single probe connected to two devices. You need to buy another probe with dual outputs.

April 23rd, 2019, 10:39 pm

I was responding to ballpencil since he said that it could be done.

I'm totally fine going the dual thermocouple route. I went onto the Omega site and wasn't sure which dual thermocouple to order that has the same dimensions as my current one.

Type : K
Temperature Range : 0-400 Celsius Degree
Thread Diameter : 7.6mm / 0.3"
Probe Diameter : 5mm/ 0.1"
Fork Terminal Spacing : 4mm / 0.16"
Probe Length : 200mm/ 7.8"
External Shielding : Metal Shield

#7: Post by **ballpencil** » April 24th, 2019, 6:12 am

coolio wrote:Should I just cutoff the end of the wire and use it to run to both devices? Also, what's the best way to connect the new sections?

Thanks!

In my case, my datalogger uses those yellow screw on connector like this: https://www.newark.com/newport-electron ... dp/20C3726

I need only combine the splicing wire and thermocouple wire to those screws.

It works, despite what others said here.

#8: Post by **baldheadracing** » April 24th, 2019, 8:56 am

ballpencil wrote:It works, despite what others said here.

Have you used a Phidget 1048 in this configuration? I have, and my experience was that the channel on the Phidget eventually failed (permanently showing wrong temps).

The setup can work with another device: an Amprobe in my case; in your case a Center. Neither experience implies that the setup will work with a 1048 ... never mind not taking into account how the various PID's could react.

#9: Post by **Almico** » April 24th, 2019, 9:21 am

ballpencil wrote:In my case, my datalogger uses those yellow screw on connector like this: https://www.newark.com/newport-electron ... dp/20C3726

I need only combine the splicing wire and thermocouple wire to those screws.

It works, despite what others said here.

If the input impedances are not exact on both devices, they will not work well. Even then, I would not bet the farm that the readings are not consistently accurate. If they are, you should play the lottery a lot. But it's irresponsible to go against all conventional advice and wisdom and recommend others follow in your fortunate footsteps.

#10: Post by **OldNuc** » April 24th, 2019, 9:33 am

A thermocouple junction is a current generator, wiring in parallel will produce unreliable results. Splicing thermocouple wiring tends to produce another junction in series with the primary junction which skews the final results in a random and unpredictable manner.