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Flow Sensors

How to choose the right one to suit your water dosing task and your Select doser type.

There are a lot of farmers across Australia with a need to add something into the drinking water for their Livestock. Most of these applications have one thing in common: The need for dosing to be automatically adjusted in proportion to the water flow.

When we first launched the Select Doser in Australia about 16 years ago, there were only a couple of options available for Water Flow measurement. We had sensors in our range to measure very small and very high flows, but very little to cover the middle of the range that people encounter on farm.

This meant that our customers in the early years could use the Select Doser for precision applications (such as a Poultry Shed, or Weaners on a pig farm) or Farm-wide applications (such as Water treatment with Chlorine or Peroxide), but didn’t have a good solution for intermediate applications (Dosing a decent sized group of cattle independently, or multiple sheds on a piggery).

As you’ll see below, things have changed. We now have a range of flow measurement devices to cover, not just any flow situation, but also dramatic differences in source water quality.

Flow Sensors vs. Flow Meters – What’s the difference?

Flow Meters

In the field of water dosing, a water meter is a basic flow measurement device, commonly available from any number of water equipment suppliers around Australia. These are used for many domestic and agricultural applications, especially those requiring a low level of precision. Typical flow meters have a K factor of either 1, 10 or 100. This means that each pulse output from the meter is equal to 1, 10 or 100 litres of water.

In water dosing applications, these kinds of meters are really only effective for products that don’t require a lot of precision. Think about concentrated products dosed into very large flows. Chlorine or other water treatment products can be used effectively with these types of meters, they still aren’t the best option.

There’s nothing wrong with using a flow meter in these situations. We just want to emphasize that they will never match a flow sensor for accuracy.

Flow Sensors  

In the context of water dosing, a flow sensor is superior to a flow meter. These are precision measurement devices. Where the flow meters measure in multiple litres per pulse, these sensors will output multiple pulses (sometimes hundreds of them) per litre that flows through them.

There are flow sensors for just about any application, as you’ll see below. Many of our customers who buy Select Dosers from us are doing so because they want the precision that they provide over other types of machine (such as pressure driven water dosing equipment)

Types of Flow Sensors supported by Think Livestock

There are two main types of flow sensor that Think Livestock commonly use with our devices: Turbine Flow Sensors and Magnetic Flow Sensors.

Turbine Flow Sensors are suitable for 95% of applications in water dosing. They use the same basic principle as standard flow meters, but with a much higher level of precision. All of the sensors mentioned above are turbine types and the main thing to determine your choice is the diameter of the water pipe you are dosing into and the expected peak water flow. However, one more thing needs to be considered before making your choice. If the water you are dosing into has high levels of particle matter which can’t easily be filtered out, a magnetic flow sensor might be justified. These are much more expensive so you would normally only choose to use one in extreme cases.

Magnetic Flow Sensors utilize a stable magnetic field to meter the water flow passing through the line. These sensors require the line to be pretty much full at all times to be effective, but they are also a lot more reliable than other sensors in dirty water, where filtration is not practical.

We have a broad range of options for both types of sensors, and some alternative options for flow (or other parameter) measurement that I’ll briefly touch on at the end.

Turbine Flow Sensor Specifications

VTY10 – ¾” Turbine Sensor

  • Flow range: 20 – 1,500 litres/hr 
  • Connection: ¾” BSP male
  • Lead length: 4m

VTY20 – 1” Turbine Sensor

  • Flow range: 48 – 3,600 litres/hr
  • Connection: 1” BSP male
  • Lead length: 4m 

VTH25 – 1 ¼” Turbine Sensor

  • Flow range: 200 – 10,000 litres/hr 
  • Connection: 1 1/4” BSP male
  • Lead length: 4m

VTH40 – 2” Turbine Sensor

  • Flow range: 400 – 25,000 litres/hr 
  • Connection: 2” BSP male
  • Lead length: 2m

Magnetic Flow Sensors

MAG3 – 3/8” Magnetic Sensor

  • Flow range: 6 – 120 litres/hr
  • Connection: 3/8” BSP male
  • Lead length: 2m

MAG6 – ½” Magnetic Sensor

  • Flow range: 15 – 300 litres/hr
  • Connection: 1/2” BSP male
  • Lead length: 2m

MAG15 – ¾” Magnetic Sensor

  • Flow range: 150 – 3000 litres/hr 
  • Connection: 3/4” BSP male
  • Lead length: 2m

MAG25 – ¼” Magnetic Sensor

  • Flow range: 750 – 15000 litres/hr 
  • Connection: 1 1/4” BSP male
  • Lead length: 2m


The ability of the Select Doser to be programmed to suit a wide range of different flow sensor makes in a very versatile piece of equipment indeed. The key thing to look at before making your choice is always the expected peak water flow. If a flow sensor is too small for the job, it’s false economy to try to use it if it’s going to restrict water flow to your animals. If you need further discussion before making your choice, please give us a call.