Why Votronic sensor?
Which sensor to use was the question I asked myself when designing the WLI? There are mechanical sensors using a float, then capacitive, ultrasonic sensors and special pressure sensors on the market.
The disadvantages of mechanical sensors are their sensitivity to water quality. Surely you know the problem with limescale. Another disadvantage of resistance sensor is sensitivity. Normal sensitivity is about 2cm only. For “high resolution” models, it is 1cm. If you have a tank 30cm high then you can measure 15 or 30 levels. 15 levels are really few. You cannot shorten such a sensor to the required length, so the resulting accuracy is even worse.
The ultrasonic sensor has sensitivity is about 0,7-1,5cm but is not suitable for long-term use for people and especially if you have pets such as dogs or cats. Another problem with the ultrasonic sensor placed on top of the tank is condensed water. Just a drop on the sensor and the display will show a full tank.
Another option is pressure sensors designed as level sensors. I do not know whether or not they have compensation for changes in ambient atmospheric pressure. They are quite expensive and therefore I have not tested any.
I decided to use the Votronic sensor because it can be used in almost all tanks. It has excellent accuracy and sensitivity about 2mm and can be shortened to the required length. I worked on aircraft maintenance and repairs, and we had capacitive sensors as fuel sensors in our plane. Therefore, I have no doubt about their properties when measuring fluid levels.
I can’t make a sensor with certificates for drinking water and that’s why I opted for the Votronic 15-50K in my caravan now for 2 years. The sensor works well. The problem was the Votronic display, which shows 10% even when the tank is empty. I don’t know why this is so, but it didn’t suit me.
I designed my own and better display. Instead of 10 levels, I have 100. In the off state, I have reduced the current consumption 17 times. (from 3mA to 170uA). WLI can change its function from “Fresh water” to “Gray water”. Device can display the value in liters. Recently, I offer the possibility to program WLI for tanks with an irregular shape. No display on the market has this option. The piece is same or lower than Votronic display.
Important remark! Avoid a system that uses a flow meter as a transmitter. These systems say nothing about the actual state of the water in the tank, but about the water consumed. You can easy recognize such a system: The transmitter is mounted on a pipe, not in a water tank. In the event of a pipe failure and a water leak, the system will show you the water value before the failure, not the actual condition. In operation using such a system you still have to refuel water tank to the same water level otherwise an incorrect value will appear. For the same reason we do not use flow meters as a fuel gauge in our cars.