I am looking to add temp sensors in my refrigerator & possibly a sensor reading supply air from my AC. What types of sensors do I need?
asked
Temp sensors for Cerbo GX
Hi @DFraizer,
you'll need the temperature sensor for Quattro, MultiPlus and Venus GX, which is also good for the Cerbo GX. See: https://www.victronenergy.com/accessories/temperature%20sensor%20qua%20pmp%20venus%20gx?_ga=2.10551028.1933131784.1590438491-1969333987.1588075539
I appreciate the answer, but the temp sensor for the multiples does not seem appropriate for a refrigerator. Will a 2 wire sensor work?
The sensor for the MultiPlus is exactly designed for such things. The big cable lug is electrically isolated as is the rest of the sensor.
So can I use the temp sensor that came with my Multiplus 12/3000 and hook it to my Cerbo and simply expose the lug to the outdoors and get a reading from that?
hello
use LM335 TO-92 sensor.
permawatt
hello
inexact, le capteur d'un M+ est une sonde LM 335Z dont la plage d'utilisation habituelle est de
- 40/+120°C ... donc parfaitement utilisable pour un frigo.
2 fils = no adjust possibilities, 3 fils= adjust possibilities 
benoit Permawatt
I made myself these.
See my post in this thread.
https://community.victronenergy.com/questions/63811/temperature-sensor-for-water.html?childToView=63865#comment-63865
These are attached to my Rpi 3B+ but they should work on a real GX device.
Hi
Yes i use those on my raspi systems and they work perfectly. I fit them into a stainless steel tube enclosure, as per photo.
Looks good, Rob. Where did you find the stainless tubing?
Nick Hardy
You an buy it anywhere on line, i do carry a stock of these tubes.
Regards
Rob D
NZ
https://www.amazon.com/50PCS-LM335Z-LM335-TO92-Original/dp/B07KPMT161
https://www.distrelec.de/en/temperature-sensor-to-92-lm335-texas-instruments-lm335z-nopb/p/17327679
https://www.walmart.com/ip/5pcs-LM335Z-TO-92-LM335-TO92-335Z-IC/2527734771?wmlspartner=wlpa&selectedSellerId=101249795
Here's another source for the component: https://www.digikey.com/en/products/detail/stmicroelectronics/LM335Z/591686
The datasheet: https://www.st.com/content/ccc/resource/technical/document/datasheet/04/fa/9d/16/39/87/44/8d/CD00000459.pdf/files/CD00000459.pdf/jcr:content/translations/en.CD00000459.pdf
One problem with the LM335Z is the absolute accuracy, from the specification data sheet the uncalibrated figure is 6C max. Not the most useful these days, you could be lucky but my experience with my sensors I've been closer to the max. I needed to add the calibrating circuit on the adjust pin and calibrate to +/- 0.5C from a known reference. Works well, the down side is extra components and where to mount. The adjust circuit is found in the LM335 Ti specification data sheet.
I would mount the calibration potentiometer right at the 335 and enclose the entire assembly in heat shrink tubing. They make heat shrink tubing with a sealant inside that would waterproof the circuitry inside. I've even done this with a long pieces of regular heat shrink and pinch the sensor end while still hot to seal it. The tubing is long enough to take the other end to an area that doesn't need to be waterproof.
To make a smaller temperature probe, you could calibrate the 335 then remove the potentiometer and replace with fixed resistor values.
There is also a way to calibrate the sensor in the GX device.
I can highly recommend RuuviTag bluetooth sensors. I have 12 of them in my house and some of them also connected to my Cerbo GX in parallel. RuuviTags can also been placed inside a fridge. Just make sure they are in range of the Cerbo.
