Does Flow Sensor reading change because of pipe diameter?

[Fishyfish22]

I'm running 1 1/4 and 1 1/2" tubing throughout my system. Neptune doesn't have a flow sensor for either of those sizes, so naturally I want to use the 2" sensor with adapters on both ends.

My question is, will this give me an inaccurate reading since flow changes in respect to the diameter of the tunnel?

There is an Inline UV being plumbed so I really want it to be as accurate as possible. This is the last thing I'm questioning in my cart before I finally place the order for my new plumbing.

 

[KStatefan]

The flow will be the same in all areas. Flow does not change the velocity does. If the velocity is to slow it would effect the accuracy. What are the specs for the minimum flow of the sensor?

 

[SuncrestReef]

The flow will be the same in all areas. Flow does not change the velocity does. If the velocity is to slow it would effect the accuracy. What are the specs for the minimum flow of the sensor?

The 2" flow sensor is rated for 300-3000 gph.

Source: https://www.neptunesystems.com/fmm-accessories/

 

[KStatefan]

The 2" flow sensor is rated for 300-3000 gph.

Source: https://www.neptunesystems.com/fmm-accessories/

If you are in that range or should work

 

[GK3]

I'm running 1 1/4 and 1 1/2" tubing throughout my system. Neptune doesn't have a flow sensor for either of those sizes, so naturally I want to use the 2" sensor with adapters on both ends.

My question is, will this give me an inaccurate reading since flow changes in respect to the diameter of the tunnel?

There is an Inline UV being plumbed so I really want it to be as accurate as possible. This is the last thing I'm questioning in my cart before I finally place the order for my new plumbing.

Neptune makes limited sizes because as you showed, you change to the size for the sensor and use one they have. For example, 3/4” pvc you either use the 1” or the 1/2”. These sensors are calibrated for their size. That is why in apex you have to specify the size.

so to answer your question, it will not give an inaccurate reading. The diagram you showed is a good one. Think conservation of mass - it must be constant (you can’t crate it or destroy it). So if you take any section of pipe along the way whatever comes into, the same amount must leave it. When you have a small diameter it has a given flow velocity and therefore mass flow rate. If the diameter changes to larger, the mass flow rate must stay the same (what comes in must go out) and therefore the velocity will slow down. A good analogy is take a garden hose and connect it to a fire hose. The water comes flying out of the garden hose but won’t come out at the same speed at the end of the fire hose.

The Neptune sensors work by measuring how fast the wheel spins and knowing the cross sectional area of the pipe at the wheel. It doesn’t matter what is up stream or downstream for the measurement (assuming it’s all full of water and not air)