Tag: measurement

Double bucket

 

Couple of years ago me and Jakke where conducting some lightning measurements. We were in a hurry and on a budget. Well, perhaps not so much on a budget as I was (and am) fond of cheap solutions. What we came up with, was a way of using some 50 mm by 50 mm sawn softwood (likely spruce or pine), some plywood and a couple of polypropylene buckets to make a fairly durable weather cover. These could be used for example as part of an open monitoring project.

Since I’m lazy, I didn’t bother to dismantle them after the measurements ended and a couple of these have been out in the weather (Southern Finland)  for about four years. Today I finally decided to take them a part. I found out that they have been holding up pretty well and would likely have been up to their task for at least a few more years. So if you are looking for a way of making a similar system, below I explain how to make them. At the end are a couple of pics and comments on the dismantled set.

White buckets were used in an attempt to keep the electronics cool. Other colors may be used depending on location to make it less visible.

Figure 1 shows a rendering of the two ways we used to setup the systems. In the left the stud is driven to the ground. I used an iron bar to first make pilot hole and then carefully using a small piece of plywood as protection (between the sledge hammer and the pillar) hammered the stud to the ground.

In the right is the system we used on a (Melbourne) Florida roof top for a couple of months to create a more temporary measurement setup. We used some concrete blocks as additional weight just in case. If you are considering a more permanent system consider adding some steel wire to attach the system to something really heavy. You don’t want it hitting someone when it is picked up by hurricane winds or a tornado.

Cheap weather cover for measurement devices
Figure 1. Cheap weather cover for measurement devices

Figure 2 shows what you need. All sizes are approximately those we used, select your bucket size to match the size of your device and scale everything else accordingly.

  1. Two short pieces of wood. One should be short enough to fit side ways in to the bucket and one should be about 5 cm shorter than the bucket is high. One long piece of wood, it will determine how high the rest of the system sits.
  2. A piece of plywood, cut a circle that fits in to the bucket to a depth of about 5 cm
  3. Two buckets
  4. Some screws and hot glue
  5. a saw, (sledge)hammer, screwdriver, eye protection etc.
Figure 2. Things you need
Figure 2. Things you need

As shown in Figure 3 set the longer of the two short pieces of wood on top of the plywood. Use hot glue or two screws or both to attach it in a manner that it can’t rotate around the vertical axis. Before this, make any openings you need for electrical wiring and such.

Figure 3. Set one of the short pieces on top of the plywood.
Figure 3. Set one of the short pieces on top of the plywood.

The shorter piece of wood is then attached on the other side of the plywood. Select the correct length for the support pillar and after driving it to the ground attach the plywood to it. If any of the wood surfaces is curved using copious amounts of hot glue between surfaces before inserting the screws will make the system more solid. The inner bucket is attached with one screw, which is driven through the bucket bottom to the piece of wood shown in Figure 3. Note that you will be driving the screw in the direction of the grain, do it carefully or the strength of the attachment will be reduced.

Figure 4. Attach the shorter piece of wood as shown and put the bucket on top of the assembly
Figure 4. Attach the shorter piece of wood as shown and put the bucket on top of the assembly.

Add the other bucket, this one stays in place by gravity and friction. If you use a screw, rain will seep in.

Figure 5. Add the other bucket.
Figure 5. Add the other bucket.
Image 1. Two systems, the outer bucket has been removed from the one on the left.
Image 1. Two systems, the outer bucket has been removed from the one on the left.
Image 2. View from below.
Image 2. View from below. Looking good, all the wood is still healthy.

 

Image 3. View inside the protected area. Apart from some spider web its like new.
Image 3. View inside the protected area. Apart from some spider web its like new.

 

Image 4. The support structure. The limiting factor for the operating life of this setup is likely rotting at the air ground interface. I was able to snap the wood by tapping the sharp end to the ground
Image 4. The support structure. Limiting factor for the operating life of this setup is likely rotting at the air ground interface. I was able to snap the wood by tapping the sharp end to the ground.

Figure 4 shows the support structure and the weak point at the air-ground interface. Rotting has reduced the strength of the wood. If the place where measurement are taken is not very sensitive, consider using wood that has been treated to protect against rot. Using a larger size like 75×75 or even 100×100 mm2 will likely also give you a couple more years of service life.

Image 6.
Image 5. Ultra violet radiation has made the plastic brittle. Some erosion was also visible on the surface. Note the white stuff at the end of the screw. This screw was used to hold the inner bucket in place and the Zinc protection was showing signs of wearing out.
Image 6. Markings at the bottom of the bucket.
Image 6. Markings at the bottom of the bucket.

 

The mathematics of equality

[T]he data suggest that all humans are equal, as long as one is measuring the wrong thing with the wrong instrument. The same methodology also points to the unity of all beingness.

In Finnish / suomeksi: click here. More postings in a similar vein: WeirdMath.  

Derawi et al 2010 showed that it is possible to identify a person with nearly 80% accuracy by using just a simple accelerometer on a mobile phone. Peoples’ walking styles are different and consistent, and analysis of the gait can identify the person.

In this follow-up study we determined whether a test person can be identified from accelerometer data when the person only stares at the mobile phone. There were 34 test subjects. Part of the test (14 subjects) was a classical double-blind study, in which the participants had no idea what they were supposed to be doing. Part of the test (20 subjects) was a postmodern triple-blind study, in which the subjects did not know that they were participating (the phone was simply placed close to them without the subjects noticing anything).

The experiment was done by placing a pink Samsung Galaxy S2 on the table, and recording its accelerometer data with the AndroSense software. Data were stored at 50-millisecond intervals. The participants were asked to stare at the phone for 20 seconds. In the triple-blind test, logging was done for 20 seconds without telling the test subject. Eight-second samples of all measurements were taken for further analysis.

As a pilot, the test was extended to some animals, as well as other forms of sentient existence. It is unclear whether the pilot was double-blind or triple-blind, as the test subjects did not seem to understand the instructions they were given.

Figure 1: All data. The x-component of the accelerometer was used. To account for tilts, the data were normalized to zero by subtracting the average. An ANOVA test was run.

All

 

Figure 2: Four typical human profiles. It is not possible to statistically identify the test subjects. Age and gender do not affect the results.

People

 

Figure 3: Four animal profiles (dog, cat, cow, bug). The animals cannot be distinguished from one another, nor indeed from humans.

Animals

 

Figure 4: Other organic subjects: an apple, a tree, a woolen sock, and some navel fluff. Since the sock was dirty and the fluff was fresh, it can be reasonably assumed that all subjects were sentient. The profiles cannot be distinguished from the other test subjects.

Other

 

Figure 5: The ANOVA test shows that the null hypothesis cannot be rejected for any subjects. There are no statistically significant differences between any of the subjects.

Anova2

This means that a mobile phone’s accelerometer cannot determine who is staring at the phone. More fundamentally, the triple-blind test shows that the accelerometer cannot even determine whether the subject knows he is supposed to be staring at the phone. The experiment thus shows no differences whatsoever between people.

Extending the study to non-human subjects suggests that there is no statistically observable difference between for example an engineer, a cow, and navel fluff.

In summary, the data suggest that all humans are equal, as long as one is measuring the wrong thing with the wrong instrument. The same methodology also points to the unity of all beingness.

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