Let’s take a look at some of the technical details behind Tank Utility’s propane level monitoring system. In this post we’ll cover some of the hardware design choices which we made for accuracy, safety and reliability, with more details on our cloud-based architecture (including database and software choices) to come in the future.
The Sensor Technology
We decided to leverage a Hall effect sensor for reading out the fuel level within a tank. All tanks above 100 lbs (i.e. a small tank with less than 40 gallon capacity) have a few of the essential parts to make this work. Here’s a look at the magic behind the sensor.
- The tank has a float. Because propane exists as both a gas and a liquid when contained in a pressurized tank, the tank uses a mechanical float to determine the liquid level.
- The tank has a rotary gauge to visually inspect the level connected to the float. Luckily, there are some very common gauge designs which help ensure our solution works for your tank.
- The rotary gauge has a magnet. The magnet’s position creates an AC field which is translated into a proportional voltage by the Hall effect sensor. This is technology that has been used for years by the automotive industry.
Simple right? Unfortunately, when you’re dealing with magnets, moving mechanical parts, phase changes and varying weather conditions, there’s plenty of fun challenges to get a highly calibrated reading. Data Quality is fundamental, so we’ve worked through those details and are confident that the accuracy of our sensor is as good or better than any other technology on the market.
Did I mention our sensor also happens to be really simple to install? It’s non-invasive, meaning anyone can install it themselves without risk. If your gauge is R3D ready, our current sensor even uses a press-fit to connect, meaning no tools are necessary.
The Communication Technology
We are testing three different connectivity solutions:
- WiFi only — The sensor connects directly to a 2.4GHz 802.11 b/g/n wireless network. This solves the connectivity problem for most folks by leveraging their WiFi router as the gateway. To know if this will work for you, you can check your WiFi coverage at your tank.
- WiFi to low-frequency radio — This is a two-device solution consisting of (1) a gateway (AKA transceiver) within the home which will connect to the LAN through WiFi or Ethernet cable and receive data from (2) your tank’s transmitter through low-band radio frequency. This is a better solution for folks with tanks further out in their yard, and has both indoor and outdoor temperature sensors for more detailed analytics and alerting. This solution costs a little more since we have more hardware.
- Cell-based connections — This includes a monthly connection fee. This is the best solution if internet coverage isn’t an option. It also has the added benefit of connectivity in the event of a power failure.
All of the devices have a temperature sensor and a level monitor on the transmitter near the tank. They all use a battery at this location, so we’ll use a sleep mode between readings. This design keeps the device intrinsically safe and simple for anyone to install without requiring any cables or power supplies to the tank.
In the event that a reading is not sent to the database, the user will be alerted of a power or connectivity failure.
The Enclosure and Contents
Realizing that many tanks are buried and water can present a number of issues, we’ve created a water-tight enclosure to NEMA-4x rating specifications. We’ve leveraged some of the latest advances in 3-D printing to quickly test and refine the enclosure design.
The electronic bits within the enclosure as well as the sensor are all designed within intrinsic safety guidelines. This means that the device is incapable of being a point of ignition, so you can rest assured that our solution poses no risk to your home or your loved ones.
We designed this device to get its power from standard-sized batteries. Owners will receive an alert when the batteries need to be replaced, which will rarely be the case because the device is in deep sleep mode most of the time, using very little power.
And just in case you need it, we’re including a 15-foot length of cable between the sensor and the transmitter’s enclosure.