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 LM355 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.
Making a temperature sensor for the Victron cerbo GX is pretty straight forward. The sensor is a LM355 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.
- 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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