Dual output RTD options

[BrewdyQuah]

Looking for some advice here..... I have a custom electric brew panel which will be home to a new EZBoil (DSPR120) regulator. The system leverages RTD PT100 temp sensors.

I'd like to record temps throughout the brew process through a charting system (something like Grafana or Thingspeak). However I don't believe there is a way for me to pull data from the EZBoil, so my thoughts were to try and get the temperature element output sent to 2 endpoints (The EZBoil, and another ESP32 based gateway).

I understand that RTD was not built to support simple serial/parallel wiring schematics to support multiple endpoints natively. It seems like there are a few options out there (dual element RTDs, signal multipliers, PIDs that support aux output, etc.)

Before I go down the expensive rabbit hole of experimentation, I was curious if anyone has already figured out the best solution here. Appreciate the insight here.

 

[doug293cz]

Not sure it's possible to hook an RTD up to multiple temp measuring devices. Resistance measuring devices work by forcing a precise current thru the resistor under test, and then measure the voltage drop across the resistor. Two measuring devices, both trying to push precise currents thru the same resistor are just going to get in each other's way.

When controlling the heat input to maintain a mash temp, you usually want the heat controlling temp probe located as close as possible to the heating element in order to prevent local overheating (and possible scorching) of the wort. But, the bulk of the mash, which is the temperature that you actually want to maintain, and log, is usually a few degrees cooler than the wort near the heating element (thermodynamics requires this.) So, you are better off adding a second temp probe that is positioned near the center of mass of the mash, in order to measure and log accurate mash temps.

Adding a second probe gives you the option to use a different type of probe for each task, and in your case using a one-wire probe in the bulk of the mash might be easier to interface with your electronics.

Brew on

 

[Bobby_M]

I have a 4 channel temp logger with very inexpensive K thermocouples that I just shove or clip where I want them. I know it's a drag to potentially make another hole in your kettle, but that's probably the cheaper, more accurate way to go.

 

[Indian_villager]

Multiple Element RTDs are a thing where you have multiple measuring elements in the same probe that can be hooked up to different devices if you want to go that route. But in my opinion the cheaper option would just be to introduce a second probe running a DS18B20 so that whatever you have running your data recording does not need additional amplification circuits or a stable ADC. You could realistically get away with the digital sensor and an ESP32.
https://blog.lesman.com/2012/11/28/how-do-i-get-an-rtd-signal-to-two-different-devices/

 

[BrewdyQuah]

Thanks all.... Definitely confirms my suspicions. Appreciate the wisdom and experience of the board.

 

[matt_m]

I'd be interested in what you figure out as I'd like to do the exact same thing but not enough to mess with adding a probe.