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Hi all, I am running a coffee roaster with two RTDs (PT100), connected to a Phiget 1046. The 1046 is connected via USB cable to a desktop PC. I was instructed to solder resistors to my RTD wire ends, before the connection to the 1046. It works, but due to haphazard connection, I find the wires are fraying and some copper has become exposed. (Please see attached photo.)

My question is, are these resistors the typical way of connecting the RTDs? Is there an off-the-shelf solution, or a better way to connect them? I am recording the temperature data from the RTDs on a software called Cropster. Any advice is much appreciated. Thanks!

As far as I can tell from Cropster's website, it looks like they support the use of the TMP1200, which connects directly to RTDs. This would be the cleanest way to wire up an RTD.

I can't see your picture, but in general the best way to handle external circuitry like resistors is to solder them to a protoboard, provide some strain relief to the wires soldered to the board, and then enclose the board. For simple situations, you can also just solder the resistors in-line and then use heat shrink tubing to protect the wires and provide strain relief.

Hi there, thank you for the reply! My apologies, please find the picture reattached.

My question is also, do I need the external resistors that are soldered to the PT 100, in order to use the RTDs? Could I simply connect the PT 100 ends directly to the Phiget 1046, without the use of the resistors?

In reference to Cropster, there is a page that seems to indicate that I simply need to connect the two wires to the 1046. There is no mention of any external resistors.

cropster
/rtd-type-temperature-sensors-roasting-intelligence-ri-setup

On the other hand, there seems to be the alternative method as mentioned by mparadis, which is to use a Vint hub setup. This seems to be described here by Cropster as well, in a beta testing phase. Can I assume that the resistors are not required in this manner?

cropster
/vint-hub-rtd-type-temperature-sensors-roasting-intelligence-ri-setup

Pardon the amateur questions, any help is greatly appreciated! Thanks!

I checked Cropster's documentation and it's definitely incorrect. While the RTD does respond somewhat to temperature changes when hooked up this way, without an excitation voltage your measurement will be very inaccurate.

You are correct that resistors are not needed when using the TMP1200 and VINT Hub.

I've contacted Cropster about their 1046 documentation so they can have it fixed.

Hi there,

Thanks for raising the issue.
Please let me shed some light onto this.
The Phidget1046 we send out comes with resistors built in and is ready to use for RTD sensors.

We have now modified the info in our manual as a result.

If you need any help connecting a roaster or if there any further questions you can always reach us via the "contact us" form on your website.