EveryDrop flow meters are designed to be as inexpensive as possible while maintaining high levels of accuracy and reliability. That's enabled by our patented vortex technology, which is the basis of both our wired and wireless flow meters. In this article we'll talk a little bit about the differences.
You don't need us to tell you that the most obvious difference between wired and wireless flow meters is ... wait for it ... wires!
It's also obvious that our wireless meters are more expensive than our wired meters.
You may not have much choice in deciding between the two. Sometimes it's just too hard to run another set of wires under the driveway, behind the chicken coop, and around the buried fallout shelter in your backyard. Wireless may be the only option.
Our wireless meters transmit in what's called the ISM band -- Industrial, Scientific, and Medical. This is a section of the radio spectrum that the U.S. government has made available for a variety of relatively short-range applications. In the U.S. the part of it that we use, the "sub-GHz" band, is centered around 915 MHz (in other countries the frequencies are different). For comparison, WiFi transmits in the 2.4 GHz and 5 GHz (and higher) bands. Bluetooth also lives in the 2.4 GHz band.
Who cares about frequency? Well, it turns out that radio waves travel farther when they are at lower frequencies, all else being equal. Your irrigation controller may be at the other side of the house from the main water line for your sprinklers. Having more range is a good thing. So the 915 MHz band is a little better.
That means you won't see our flow meters on your WiFi router's list of devices, nor can you get Alexa or Siri to tell you the flow rate of your sprinklers (well, not easily, anyway). Nor can you connect to them with the Bluetooth on your phone.
Aside from frequency, there's also the matter of protocol. Network protocols like WiFi and Bluetooth are pretty complicated, since they have to allow the simultaneous transmission and reception of many devices, all communicating at the same time. There are similar things in the sub-GHz band -- LoRaWan is one of the most popular.
We use our own protocol because our needs are a lot simpler: for now we just have one meter (or sensor) sending flow rate information to one receiver that plugs into a smart irrigation controller. And since our wireless flow meters are powered by batteries, simpler is better. Radio waves require power: we transmit just the necessary amount of information to keep our power requirements as small as possible. Some of our newer wireless flow meters only transmit in one direction, from the meter to the receiver. This also helps extend battery life.
Our wireless flow meters have two components: a transmitter (the flow sensor), and a receiver. That means they are going to be more expensive than a wired flow meter. We need two radio CPUs, two antennas, two housings, etc.
The benefit of that extra cost to the customer is the elimination of wires. But it has another benefit as well, one that is not as easily recognized: flexibility.
The design of our wired flow meters is constrained by the electrical interface provided by the controller manufacturer. Different manufacturers expect different kinds of signals. In theory we could provide some kind of programmability to work with many different controllers, but that is limited by several factors:
- The controller provides a very limited amount of power over the standard 2-wire flow meter connection. This limits our ability to add displays and other functionality to the wired flow meter (yes, our wired flow meters have a display, but it's very basic).
- It's hard to make a good waterproof user interface, and it adds cost.
These are not insurmountable problems, but for now we've chosen to make the wired flow meters be the lowest cost solution we can think of.
The wireless meters, on the other hand, have a nice receiver unit (the UMI -- Universal Meter Interface) that is mounted indoors and has a separate 24VAC power source from the controller. That's why it has a 4-wire connection to the controller (2 for power, 2 for the flow rate signal). Since it's almost always very close to the controller, having 4 wires instead of 2 is not a big deal.
Since it's in a protected environment and has oodles of power from the controller, the UMI lends itself to having more features at little extra cost. It has a nice little display and pushbuttons for control. One of the great things the wireless flow meters can do is modify their output signals (from the UMI to the controller) to match what a particular controller is expecting. For our wired flow meters we had to decide on one particular output format. That format is not compatible with some controllers from Hunter and Yardian (for different reasons). Our wireless flow meters, however, can be easily programmed (by the user, in the field) at any time to work seamlessly with those controllers and many more. They also have flash memory that remembers those settings, and others, across power cycles.
Our wired meters are reliable, easy to use, a great value, and work over very long distances. That said, we think the future is clearly heading towards wireless. We're working hard on things like solar power to eliminate the hassle of changing batteries, and on reducing the system cost so that wireless can be as affordable as our existing wired flow meters. Stay tuned!