Quote of the Day

20 years from now, the only people who will remember that you worked late are your kids.

— Something I saw on a Reddit post. I don't recall which one. Young parents need to remember this.

## Introduction

I do not like mosquitoes — who does? To reduce the number of mosquitoes at my Northern Minnesota cabin, I decided to buy a Mosquito Magnet (Figure 1). I bought it last year, and while it ran for a while, it soon gave me an error warning (fast flashing LED) and stopped working. I live in a remote location, and getting things serviced is difficult, so I put it away for when I had time to look at it.

Unfortunately, we have quite a mosquito population this year, and my family has demanded that I take active measures to reduce the mosquito population. So I pulled the Mosquito Magnet out of storage and repaired it with the help of a Youtube video (Link).

It turns out I had a loose thermistor, and I was able to secure it in place. While repairing it, I also went through the cleaning process (Link).

I decided to do a little testing and gather a little data. In this post, I will look at the unit's rate of propane use. I will discuss its effectiveness in capturing mosquitos in a later post.

## Background

## Analysis

### Test Method

I am working this summer from my cabin's garage. During the day, I walk between the garage and my cabin multiple times. The Mosquito Magnet is along the path between the cabin and the garage, so I stop during my walk and use a fish scale to measure the propane tank weight.

I performed the test over four days because I suspected the flow rate would vary by the tank pressure. While I did not measure the tank pressure, I did measure the weight of propane in the tank, which should be related to the pressure.

### Data Analysis

#### Propane Weight Calculation

Equation 1 can be used to calculate the weight of propane left in the tank.

Eq. 1 |

where

*W*is the mass of propane remaining in the tank, which we compute using Equation 1._{Propane}*W*is the measured weight of the propane tank (my measurements). Government regulations limit the fill value on a "20 lb" tank to 80% of its volume rating for safety reasons. So my local propane vendor fills my tank to ~34 lbs, which means they put in 17 lbs of propane._{Tank}*W*is the empty weight of the "20 lb" propane tank. My tank has an empty weight of 17 lbs._{Tare}

My tank weight measurement was subject to some variation because I was holding the propane tank in the air by the scale. Fortunately, I took lots of measurements over time, and the errors should average out.

#### Vendor Propane Burn Rate Specification

The Mosquito Magnet vendor states that a 20 lb propane tank should last ~3 weeks. We can compute the expected burn rate using Equation 2.

Eq. 2 |

where

*W*is the mass of propane remaining in the tank._{Full Weight}*T*is the run time specified by the vendor (21 days)._{Specified Time }

### Visualization

#### Estimated Propane Use Per Day

The unit stopped running when the amount of propane in the tank reached ~2 lbs. Figure 2 shows the tank weight versus time on day 2 of the testing. Day 2 began with 7.7 lbs of propane in the tank — a couple of pounds shy of halfway full = 9.5 lbs = (17 lbs+2 lbs)/2. All of my data is in the worksheet attached here. The rate of use did vary by day. The more propane in the tank, the higher the burn rate.

#### Variation in Daily Propane Use with Propane Weight

Figure 3 shows how the propane burn rate varies with the weight of propane in the tank. This figure shows that the propane burn rate reduces as the tank depletes. I would estimate the average burn rate for 9.5 lbs of propane as 0.74 lbs/day = 0.70 lbs/day (7.7 lbs value)+ 0.02 lbs/day/lbs ⋅ 2 lbs. This is pretty close to the vendor's value of 0.81 lbs/day, considering the crudeness of my measurement technique.

## Conclusion

The Mosquito magnet does use ~0.81 lb/day of propane when averaged over a full tank. However, the rate of propane consumption varies with the amount of propane in the tank.