Double subscript notation
Encyclopedia
In engineering
, double-subscript notation is notation used to indicate some variable between two points (each point being represented by one of the subscripts). In electronics
, the notation is usually used to indicate the direction of current or voltage, while in mechanical engineering
it is sometimes used to describe the force
or stress
between two points, and sometimes even a component that spans between two points (like a beam on a bridge or truss
). Note that, although there are many cases where multiple subscripts are used, they are not necessarily called double subscript notation specifically.
This is a convention
to standardize the directions of double-subscript labels. The following uses transistors as an example, but shows how the direction is read generally. The convention works like this:
means the "V" from C to B. In this case, V would probably stand for voltage, C would probably denote the collector end of a transistor, and B would denote the base end of the same transistor. This is the same as saying "the voltage drop from C to B". Although this assumes what the letters are, presumably this notation can be used in other contexts.
means the "I" from C to E. In this case, I would probably stand for current, C would again probably denote the collector end of a transistor, and E would denote the emitter end of the transistor. This is the same as saying "the current in the direction going from C to E". Although this assumes what the letters mean, presumably this notation can be used in other contexts.
The names given to power supply pins on integrated circuits
are independent from the conventions used in double subscript notations. They are coincidentally named in a similar way, for example VCC.
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
, double-subscript notation is notation used to indicate some variable between two points (each point being represented by one of the subscripts). In electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
, the notation is usually used to indicate the direction of current or voltage, while in mechanical engineering
Mechanical engineering
Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...
it is sometimes used to describe the force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
or stress
Stress (physics)
In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
between two points, and sometimes even a component that spans between two points (like a beam on a bridge or truss
Truss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...
). Note that, although there are many cases where multiple subscripts are used, they are not necessarily called double subscript notation specifically.
This is a convention
Convention (norm)
A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
to standardize the directions of double-subscript labels. The following uses transistors as an example, but shows how the direction is read generally. The convention works like this:
means the "V" from C to B. In this case, V would probably stand for voltage, C would probably denote the collector end of a transistor, and B would denote the base end of the same transistor. This is the same as saying "the voltage drop from C to B". Although this assumes what the letters are, presumably this notation can be used in other contexts. means the "I" from C to E. In this case, I would probably stand for current, C would again probably denote the collector end of a transistor, and E would denote the emitter end of the transistor. This is the same as saying "the current in the direction going from C to E". Although this assumes what the letters mean, presumably this notation can be used in other contexts.The names given to power supply pins on integrated circuits
IC power supply pin
Almost all integrated circuits have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the IC's power supply pins...
are independent from the conventions used in double subscript notations. They are coincidentally named in a similar way, for example VCC.