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# 2.2.1 Abbreviations and Acronyms

Table 2-1.Abbreviations and Acronyms
Abbreviation | Description
--- | ---
ADC | Analog-to-Digital Converter of the AFE, consisting of a PGA, a Δ/Σ modulator, and followed by an integrated sinc decimation filter
AFE | Analog Front End
BAMS | Binary Angular Measurement System. Angles are normalized to the binary range [-1.0000, +0.9999] k, where k may represent any convenient scale, such as 180°, or π-radians. In this metering discussion, all angles are drawn as if vectors starting to 0° (3 o’clock position) and rotating counter-clockwise for positive phase increases. Using BAMS allows for graceful rollover from ±180º to ∓180º without edge-effects.
Δ/Σ ADC | Delta-Sigma Analog-to-Digital Converter, an over-sampled converter with noise shaping
CT | Current Transformer sensor
DB | Demo Board
DNP | Do Not Populate
DSP | Digital Signal Processor
GPGA | Gain selected for use in the ADC front end
GPIO | General Purpose Input/Output
Kh | Watt-hour meter constant for electro-mechanical meters, defines an amount of energy indicated by one (1) pulse generated by the meter and does not usually apply to solid-state meters
Kt | Watt-hour meter test constant for solid-state meters, defines an amount of energy indicated by one (1) optical pulse generated by the meter and does not usually apply to electro-mechanical meters
LCD | Liquid Crystal Display
MCU | Microcontroller Unit
MSB | Most Significant Bit, the left-most bit of a binary number
N | The number of samples in any one measurement interval. This number may vary for each measurement interval.
NA | Not Available
OSR | Over Sample Rate
PGA | Programmable Gain Amplifier: The ADC channels could have an internal, selectable, programmable gain amplifier that can provide an additional analog gain equal to GPGA
SDK | Software Development Kit
SoC | System-on-Chip
TOU | Time of Use
VP, VP-M | Voltage potential: VP is the voltage measured from node P to an implied neutral reference voltage. VP-M is the voltage measured from node P to node M, where a positive voltage is indicative of a voltage rise from node M to node P. All phase diagrams are drawn as if mathematical vectors starting at 0° (3 o’clock) and rotating counterclockwise for positive phase increases, with 90° being at 12 o’clock, 180° at 9 o’clock and 270° at 6 o’clock.
Qformat | To prevent ambiguity, this document uses the following definition of Qformat numbers, being a fixed-point number format representing both integer and fractional numbers, and may be unsigned (uQm.n) or signed (sQm.n). Unsigned Qformat numbers: An (m+n)-bit unsigned number is designated uQm.n. It occupies (m+n) bits and is stored as an unsigned fixed-point binary number. An unsigned uQm.n number may represent numbers in the range: [0, +(2m - 2-n)]. Signed Qformat numbers: An (m+n+1)-bit signed number is designated sQm.n. It occupies (m+n+1) bits and is stored as a signed fixed-point binary number, where the MSB is used as a sign bit. A signed sQm.n number may represent numbers in the range: [-(2m), +(2m - 2-n)]]. For example, an 8-bit sQ4.3 format number has one (1) sign bit, four (4) bits to the left of the binary point and three (3) bits to the right of the binary point and may be used to represent numbers in the range: [-(24), +(24 - 2-3)]] = [-16, +15.875] To convert a sQm.n format number to a decimal equivalent, divide the equivalent twos-complement binary number by 2n. For example: an 8-bit signed sQ2.5 number: [0b0100 0001] = 65/(25) = 2.03125, an 8-bit [0b1100 0001] = -63/(25) = -1.96875. To convert a decimal number into a sQm.n format number, multiply by 2n and convert to a signed two’s-complement (m+n+1)-bit number. For example: -7.33 => sQ3.4: (-7.33)*(24) = -117 => -[0b0111 0101] => [0b1000 1011]. Example-1: sQ1.14 A signed 16-bit number, having 1 sign bit, 1 integer bit to the left of the binary point, and 14 mantissa bits to the right of the binary point that can represent numbers in the range: [-2.0, +1.999938965]. Example-2: uQ2.14 An unsigned 16-bit number, having no sign bit, 2 integer bits to the left of the binary point and 14 mantissa bits to the right of the binary point that can represent numbers in the range: [0, +3.999938965].

Rev: E