1 Definitions, Acronyms and Abbreviations

Table 1-1. Abbreviations and Acronyms
Abbreviation	Description
ADC	Analog-to-Digital Converter of the ATSENSE AFE, consisting of a PGA, a second-order Δ/Σ modulator, and followed by an integrated third-order sinc³ decimation filter. A digitized conversion of an analog voltage, V_{ADC_in}, is created using the following equation: For best linearity, the product of ADC input voltage and the PGA gain must not exceed 0.5V, G_PGA×V_ADCin≤0.5V, where G_PGA for all voltage channels is fixed at 1.
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.
CT	Current Transformer
Δ/Σ ADC	Delta-Sigma Analog-to-Digital Converter, an over-sampled converter with noise shaping
DSP	Digital Signal Processing
G_PGA	Gain selected for use in the ADC front end, G_PGA, on current measurement channels only (G_PGA gain for voltage channels is fixed to 1). G_PGA = [1, 2, 4 or 8]
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.
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.
OSR	Over Sample Rate
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, +(2^m - 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: [-(2^m), +(2^m - 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].
PGA	Programmable Gain Amplifier: The four ADC channels associated with the current measurement have an internal, selectable, programmable gain amplifier that can provide an additional analog gain equal to GPGA. G_PGA = [1, 2, 4 or 8]
V_P, V_P-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 counter-clockwise for positive phase increases, with 90° being at 12 o’clock, 180° at 9 o’clock and 270° at 6 o’clock.

ADC

Analog-to-Digital Converter of the ATSENSE AFE, consisting of a PGA, a second-order Δ/Σ modulator, and followed by an integrated third-order sinc³ decimation filter. A digitized conversion of an analog voltage, V_{ADC_in}, is created using the following equation:

For best linearity, the product of ADC input voltage and the PGA gain must not exceed 0.5V, G_PGA×V_ADCin≤0.5V, where G_PGA for all voltage channels is fixed at 1.

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.

CT

Current Transformer

Δ/Σ ADC

Delta-Sigma Analog-to-Digital Converter, an over-sampled converter with noise shaping

DSP

Digital Signal Processing

G_PGA

Gain selected for use in the ADC front end, G_PGA, on current measurement channels only (G_PGA gain for voltage channels is fixed to 1).

G_PGA = [1, 2, 4 or 8]

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.

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.

OSR

Over Sample Rate

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, +(2^m - 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: [-(2^m), +(2^m - 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].

PGA

Programmable Gain Amplifier: The four ADC channels associated with the current measurement have an internal, selectable, programmable gain amplifier that can provide an additional analog gain equal to GPGA.

G_PGA = [1, 2, 4 or 8]

V_P, V_P-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 counter-clockwise for positive phase increases, with 90° being at 12 o’clock, 180° at 9 o’clock and 270° at 6 o’clock.