Victron Energy Temperature sensor QUA/PMP/Venus GX - ASS000001000
If you have a Victron solar system, you probably have a Cerbo GX and if you do you might want to make use of some of the inputs that are on offer. I wanted to use the temperature inputs, however when I looked at the Victron sensor I was shocked by the price. Having done some research I found the component that the sensor is at a fraction of the cost. So much so I bought all the components for 10 for around the price of one genuine sensor.
The sensor is really straightforward to build, simply solder two wires to the LM355 and cover with a bit of heat shrink. You can just plug a LM335 directly into a Cerbo GX but you're only measuring the temp at that point. Adding a length of cable allows to mount the sensor at a remote location. You can have a reasonable length with little degradation to sensor accuracy, 22awg cable can be upto 600ft/200m before a 1°C drop in accuracy.
I started off with heat shrink protecting the cable device interface, this is fine for internal measurements. However I wanted to have a couple of external temperature readings, I thought it would be best to provide some better protection. I did toy with using a cable lug ala the Victron sensor, but went with a stainless steel tube as it has more mounting flexibility.
Temperature Sensor
Making a temperature sensor for the Victron cerbo GX is pretty straight forward. The sensor is a LM335 in a TO-92 package is a 3 pin device, although you only need two of them. The Adj pin can be ignored as it's optional you only need to connect plus / minus.
Instructions
- Identify the two pins that need to be connected
- Optional Trim the Adj pin
- Strip the ends of a length of cable (as long as you need it to be)
- Split a short section of the cable
- Slip some heat shrink on to each cable
- Solder the cable to the LM355
- Heat shrink over the solder joints and shrink
- Strip the other end of the cable and crimp on ferrules
- Test the sensor
- Cut a length of tube
- Slip the sensor in so that the end of the tube and the top of the sensor are level
- Fill the cable end of the tube with potting compound
- Slip heat shrink over the tube and cable and shrink
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Jimmy
Keep getting reverse polarity warning in the Victron Console when trying to do this. Any ideas?
Ian Carruthers
Other than checking it is connected up the correct way, did you try swapping the wires round?
Could it be that you have used the wrong pins on the component, maybe used the adj pin instead of the negative?
Mine have all worked first time so far, it could be a defective component, not sure what results a failed component would give though.
A Johnson
Thanks for the guide. I purchased LM335Z and connected to the cerbo but it’s 9 degrees to high. Any idea how I use the adjustment pin to correct this?
Ian Carruthers
I haven't done it and interestingly my multiplus with the Victron version reads 4 degrees under. I believe from the data sheet that you would put a potential divider from the positive to the negative with the centre point going to the adjustment pin. The circuit diagram for this is at the bottom right of the first page of the data sheet :https://www.ti.com/lit/ds/symlink/lm135.pdf
Hope that helps
Brad Silvernail
Thank you for the guide. This is pretty cool. I have a Cerbo-S GX. Which connector/terminal block did you connect the two sensor wires to? The digital input? Do you have any screens shots of the programming to enable this?
Thx.
Ian Carruthers
Ah, I have the Cerbo GX which has dedicated temperature ports for these sensors. These are just plug and play no set up required. The digital input is an On/Off input so wouldn't be any help, I would say you'd have to use a USB interface or a bluetooth sensor on the Cerbo-S GX.