Solar Clock Object Attributes - Metasys - LIT-1201793 - Software Application - Site Management Portal - 12.0.50

Metasys Site Management Portal Help

Brand
Metasys
Product name
Site Management Portal
Document type
User Guide
Document number
LIT-1201793
Version
12.0.50
Revision date
2023-06-02
Language
English

This object contains attributes common to many Metasys system objects. These common attributes are described in the Common Object Attributes section. This section includes attributes of the Focus/Configuration tab, the Diagnostics tab (if applicable), and any other tab specific only to this object. See the Object and Feature Tabs section for information on the attributes that appear on the other tabs of this object (for example, the Hardware and Options tab appear on point objects).

Note: For correct sunrise and sunset calculations, you must apply north/south and east/west rules. North latitudes are preceded by a plus, South latitudes are preceded by a minus. West Longitudes are preceded by a minus, East Longitudes are preceded by a plus. See Table 1.
Note: In the Notes column, letters indicate the following: In the notes column, letters indicate the following: A - Archive, C - Configurable, W - Writable.
Table 1. Solar Clock Object Attributes - Focus/Configuration Tab

Attribute Name

Notes

Initial Value

Values/Options/Range

Description
Present Value    

1 = Day

0 = Night

Represents an Enumeration value that is true when the current time is between the computed time of Sunrise and Sunset, where 1 = Day and 0 = Night.

Latitude

W,C,A

 

Units = Degrees Angular

Range = -90–90

Defines the angular distance, in decimal degrees, of the current location north or south of the equator. Lines of latitude are also known as parallels. The International standard defines north latitudes as positive values.

Longitude

W,C,A

 

Units = Degrees Angular

Range = -180–180

Defines the angular distance, in decimal degrees, of the current location east or west of the Prime Meridian. Lines of longitude are also known as meridians. The International standard defines east longitude as positive values.

Periodic Update

W,C,A

5

Units = Minute

Range = 2–60

Determines how often sun position and Present Value attributes update during normal operation. The default value is 5 minutes.

Azimuth    

Units = Degrees Angular

Defines the angular measurement in a spherical coordinate system. The vector from an observer (origin) to a point of interest (sun) is projected perpendicularly onto a reference plane; the angle between the projected vector and the reference vector on the reference plane is called the azimuth. It is defined as the angle from due north in a clockwise direction.

Elevation    

Units = Degrees Angular

Defines the angle between the direction of the geometric center of the sun's apparent disk and the idealized horizon.

Sunrise    

Display = HH:MM

Defines the time of apparent sunrise in hours and minutes. Sunrise may not occur in the same calendar day as sunset. Due to changes in air pressure, relative humidity, and other factors, we cannot predict the exact effects of atmospheric refraction on sunrise time. The error may increase with higher latitudes (closer to the poles).

Solar Noon    

Display = HH:MM

Defines the time when the sun crosses the meridian of the observer's location. At solar noon, a shadow cast by a vertical pole points either directly north or directly south, depending on the observer's latitude and the time of year.

Sunset    

Display = HH:MM

Defines the time of apparent sunset in hours and minutes. Sunset may not occur in the same calendar day as sunrise. Due to changes in air pressure, relative humidity, and other factors, we cannot predict the exact effects of atmospheric refraction on sunset time. The error may increase with higher latitudes (closer to the poles).

Offset

W,A

 

Units = Minutes

Range = -60–60

Defines an offset to the computed Sunrise and Sunset times. The offset value is used to compute Present Value. A positive value makes the day longer and a negative value makes the day shorter.

Equation of Time    

Units = Minutes

Represents an astronomical term accounting for changes in the time of solar noon for a given location over the course of a year. Earth's elliptical orbit and Kepler's law of equal areas in equal times are the factors behind this phenomenon.

Solcar Declination    

Units = Degrees

Defines the declination of the Sun. The declination varies from 23.44° at the winter solstice in the northern hemisphere, through 0° at the vernal equinox, to +23.44° at the summer solstice. The variation in the solar declination is the astronomical description of the sun going south in the northern hemisphere for the winter. For a ground-based view of the seasonal solar paths for different latitudes, use 0° for the Equator, 23°N for the Tropic of Cancer, 40°N for Boulder, CO, 71°N for the Arctic Circle, and 90° for the North Pole.