Analog Devices ADSST-EM-3040 - Manual (Page 3)

ADSST-SALEM-3T
Rev. 0 | Page 3 of 24
EASY CALIBRATION
The ADSST-SALEM-3T chipset has highly advanced calibration
routines embedded into the software. Ease of calibration is the
key feature in this chipset. By sending specific commands to the
ADSST-SALEM-3T chipset, the dc offsets and gains for all volt-
age and current channels can be calibrated automatically. Active
and reactive power calibration is also available for fine-tuning
the errors.
The meter and calibration constants are stored in an external
flash memory, and the lock/unlock calibration feature enables
protection of the calibration constants. The ability to upgrade
the firmware residing in the flash memory makes the meter
adaptable to future needs.
EFFECTIVE PHASE COMPENSATION
The ADSST-SALEM-3T chipset employs an algorithm (patent
pending) for phase compensation. The ADSST-SALEM-
3T chipset based meter, which is very effective and user friendly,
can be calibrated for phase compensation at three current
points to cover the complete current range. This also reduces
the cost of the end product by reducing the cost of the sensing
elements, i.e., current transformers.
EASE OF DESIGN
Designing a complete meter using the ADSST-SALEM-3T is
very easy with the ADSST-SALEM-3T-DK developer’s kit. The
kit in the UART mode enables a user to evaluate and test the
computational element by connecting to a PC, without building
the complete hardware.
QUADRANT AND OTHER CONVENTIONS
The metering data computed by the ADSST-SALEM-3T chipset
uses the following conventions for various parameters:
• Figure 2 gives the quadrant conventions used by the
chipset.
• Import means power delivered from the utility to the user.
• Export means power delivered by the user to the utility.
• Total means total of all three phases.
Import and export are with reference to consumption.
U, I: Magnitude of voltage and current
P: Active Power (U × I × cos Φ)
Q: Reactive Power (U × I × sin Φ)
Φ:
Phase angle from the standpoint of I with respect to U,
always positive in counterclockwise direction.
Phase U: L1 = 0° Abs
L2 = 240° Abs
L3 = 120° Abs
QUADRANT II QUADRANT I
P–Q– P+Q–
ACTIVE EXPORT
REACTIVE EXPORT
REACTIVE IMPORT
L1, L2, L3
ACTIVE IMPORT
REACTIVE
SIN Φ = –1
REACTIVE
SIN Φ = +1
(–90° Φ)
(90° ABS)
(0° Φ)
(0° ABS)
(+90° Φ)
(270° ABS)
(±180° Φ)
(180° ABS)
ACTIVE
COS
Φ = +1
ACTIVE
COS Φ = –1
ACTIVE
CAPACITIVE (LEAD)
ACTIVE
INDUCTIVE (LAG)
QUADRANT III QUADRANT IV
P–Q+
IQ
I
Φ
P+Q+
03738- 0- 002
Figure 2. Quadrant Conventions