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We live in an intensely digital world, and almost all of the visualizations and data we encounter are created or recorded by a computer. Still, there are devices that collect and “visualize” parts of the world around us. They turn things that are ordinarily invisible (electricity, magnetism, pressure, time) into things we can see, so that we can reason about them more effectively.
These tools fit into three different categories: the first two are devices whose names often end in -meter and -graph (we’ll call them meters and graphs), and the third category is physical and chemical processes.
Meters don’t always do much visualization. In fact, they often do the opposite of visualization, quantifying something that is already visual. Graphs can record data, and typically show a time series in a line chart. Physical and chemical processes make stuff visible using the properties of a material.
We use many of the devices in this group frequently: rulers, speedometers, protractors, scales, water meters, clocks. There are also many devices that are less commonly used, like planimeters for measuring area, or tribometers for measuring forces. These don’t really visualize anything, though; they are mostly for quantifying.
There are, however, a few meters that blur the line between quantifying and visualizing. Thermometers and measuring cups use height to show temperature and volume, respectively. Galileo thermometers (below, left) show temperature using vertical position. Plastic strip thermometers use liquid crystals (just like mood rings) to encode temperature as color. Hour glasses use volume to show time passage. Barometers use height to show atmospheric pressure. Crookes radiometers use the speed of spinning fins to show light quantity. Electrometers (below, right) have thin gold fins that adjust their angle based on electrical charge.
Individually, these devices are good at showing a single data point. Sometimes, though, they can be put together to show a whole data series. The image below, by Dayna Mason, uses lots of compasses to show the distribution of a magnetic field.
Lots of combined meters can show multiple points in space at once, but graphs can show multiple points in time at once. These devices typically use a turning roll or a disc of paper with a needle that records the data over time. This method also just happens to create a visualization. Some examples of these devices include seismographs, barographs, hygrographs, and thermographs. The image below is of a combination thermo-hygrograph.
Many of these devices require electricity to drive the drum or disc, but some of them also require electricity to do the sensing. They are still analog devices — there is no need for a processor or discretization of any of the data — but they still use electronic components. Electrocardiographs measure the electrical activity of the heart over time. Electroencephalographs measure the electrical activity in the brain.
An interesting pattern in all of these “graphs” is that they all produce line charts. This happens for two reasons. First, the data they collect is continuous just like a line chart. Second, the motions required to produce a line chart are easily mechanized. A constant horizontal motion is produced by turning the drum or disc, while the data affects the movement of the drawing arm.
One of the unique properties of these machines is they record truly continuous data. Computers break data down into little chunks to be able to process it. That can be broken down into ever smaller time chunks (1 second, .5 seconds, 1 millisecond, etc.), but it is still only sampling an instant, not every moment of time like these analog devices. This continuity produces some very robust data and visualizations. The sampling process that computers have to go through can accidentally crop out a peak or dip in the data value. With these analog devices, the potential for that type of accident is gone.
Physical and Chemical Processes
Some devices rely on physical and chemical processes to visualize or record things. One of the most common tools using chemical processes is a pH strip for measuring the acidity and basicity of a chemical. You may remember them from your high school chemistry lab. They encode the potential hydrogen of a chemical as color. Another is photographic film using chemicals that react to light to record the amount (and color) of light coming from a location.
An interesting device that uses physical processes is a cloud chamber. Cloud chambers use a liquid at the right temperature and pressure to be right on the edge of boiling. Ionizing radiation particles hit the liquid and add enough energy to cause tiny bubbles as they travel along their path. The more bubbles per trail, the more energy the particle had; the more trails, the more particles.
Analog visualization and measurement devices can offer a lot of advantages in certain situations. Many of them require no external energy source to run. They constantly monitor instead of sampling at discrete intervals. They also have downsides, though. Their results are harder to share, and the data is often either locked into the recording medium or lost to time. The visualizations they produce are optimized for efficient output from the device, not for human perception. It really makes you appreciate the upper hand that computers give us: We should be grateful for the opportunity and the ability to structure and form our visualizations for people to view, study, or simply enjoy.