Direct sunlight activates the Campbell-Stokes Sunlight Logger.
A sunlight logger is a device that measures the amount of sunlight a particular region or area receives at any given time. There are a few different types of recorders, usually with slightly different specifications. The ways they work may also differ, but the end result is generally the same: get an accurate and reliable reading of solar input. Many of these types of devices are more or less permanent. They may be technically portable, but in most cases they are used to collect readings in the same place over an extended period of time, so averages can be tabulated and comparisons made month-to-month, year-to-year, and decade-to-decade. . Researchers use this data for all sorts of things. Weather forecasts and heat indexes are some of the more common applications, but solar output readings are also important for things like architectural efficiency and building considerations. The most accurate and reliable loggers tend to be very bulky and often very expensive, but smaller readers are becoming more widely available for more casual users.
basic concept
The sun provides most of the critical energy needed to support life on Earth and is a powerful force. However, solar radiation is not uniform everywhere. The Earth’s distance from the sun at different times of the year plays a role, to be sure, but there are also a number of other factors (energy absorption by nearby materials, the density of the natural landscape, etc.) that can affect the amount total amount of radiation penetrating a given location. The main idea behind a sunlight recorder is to quantify solar energy when it reaches Earth and measure its strength and volume.
marvin recorders
There are several different tools that researchers can use to obtain solar readings. One of the oldest is the Marvin engraver. This device is powered by a chronograph watch and works with the help of two colored lamps, and it works by measuring the pressure of the hot air inside the lamps, which in turn forces the mercury into a compressed tube in the same way as a thermometer. In this way, the device turns the change into a meaningful and traceable number that can be used by researchers and academics. This type of device generally works best in direct sunlight, although it can still read most of the radiation on overcast or cloudy days. However, these readings are not always that accurate.
Campbell–Stokes recorders
One way to measure the duration of sunlight is with a Campbell-Stokes Sunlight Logger. This is one of the most used devices in the category. It consists of a glass beaker or sphere that directs sunlight onto a card that is treated with a special chemical. Sunlight burns or leaves a mark on the card. This markup, called a script, is measured and converted to a time duration.
The card is normally changed once a day. It is relatively accurate and provides a total duration of sunlight to the nearest tenth of an hour, every day of the year. The sun changes altitude several times throughout the year, and in most cases three different charts can also be used. The cards are associated with the different seasons of the year and are created to adjust to the elevation of the sun.
Blake-Larsen recorders
Devices known as “Blake-Larsen” recorders tend to be some of the most technologically advanced. They work with computer software programs and most will translate your results directly to websites or web-hosted databases almost instantly. The actual processing is similar to the Campell-Stoke model, but the way the results are tabulated and reported is often very different.
These types of loggers are generally very popular with government weather agencies as well as private interest groups who want to monitor radiation at a given location. Architects and engineers are also often interested in the near-instantaneous results of these types of readings, as they can help determine the best places to build and the most advantageous location for things like solar panels.
Less intensive models
The electronic solarimeter is a newer, smaller and simpler device with a similar purpose. You can read the intensity of solar radiation and express your data in watts per square meter. In general, solar radiation can take one of two forms: direct or diffuse. If it is direct radiation, the radiation strikes the solarimeter directly from the sun. In the case of diffuse radiation, on the other hand, it reaches the solarimeter after being scattered by dust, particles in the atmosphere and gas molecules. Readings from these and similar devices aren’t always as accurate or detailed as more intensive loggers, but for more casual purposes they can work just as well for a fraction of the cost.