INTRODUCTION
THE SA2002D PIN PROGRAMMABLE MONOCHIP
METER
This application note describes the functionality of the
SA2002D metering integrated circuit using the PM2002DP
evaluation module.
The SA2002 enables the meter manufacturer to build a meter
that measures the energy consumption, and records it to a
mechanical counter. Energy flow direction as well as energy
metering activity is indicated by means of LEDs. This
application note will focus on the practical use of the SA2002D,
more detailed information specific to the SA2002D can be
found in the applicable datasheet.
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Application Note:
Energy Meter Evaluation Module
PM2002DP
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SPEC-0088 (REV. 1)
08-11-00
Setting
6A / 220V
10A / 220V
20A / 220V
30A / 220V
40A / 220V
60A / 220V
80A / 220V
Pin Status
R0 = 0, R1 = 0, R2 = 1
R0 = 0, R1 = 0, R2 = 0
R0 = 1, R1 = 0, R2 = 0
R0 = 1, R1 = 0, R2 = 1
R0 = 0, R1 = 1, R2 = 0
R0 = 0, R1 = 1, R2 = 1
R0 = 1, R1 = 1, R2 = 0
Calibrated
LED imp/kWh
6400
6400
3200
3200
1600
1600
800
CONNECTORS ON MODULE
The PM2002DP module connects directly to live and neutral
on SCK1. The module is referenced to live and should be kept
in mind when connecting test equipment to the module. The
current is measured by the shunt on the top of the PCB. The left
terminal of the shunt is connected to live. The live out will be
connected to the right terminal of the shunt.
Table 1: A summary of the pin settings possible with the
SA2002D. Pin status 0 indicates connection to VSS and 1
indicates connection to VDD.
Name
SCK1
JP2
JP3
Function Description
Mains connector for module power and voltage
sense
Optional current transformer connector.
(Underneath shunt resistor)
Optional Stepper motor connector. (Remove jumper
J6 to disconnect impulse counter)
Table 2: Connector descriptions
Live In
Neutral
Live Out
Figure 1: Connection and jumper settings for 80A / 220V bi-directional meter module
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MODULE SETUP
The PM2002DP module is setup for use with the SA2002D integrated circuit. Resistor values used on the module are calculated for
rated conditions of 80A/220V.
IIN
IIP
Vref
R2
R1
R0
FAST
Vdd
CNF
NC
AGND
IVP
DIRI
DIRO
NC
MON
Vss
LED
MOP
NC
P4
P5
P6
P7
P8
P9
P10
J3
P17
P16
P15
P14
P13
P12
P11
P18
J4
Vdd
Vss
J15
Vdd
Vss
J14
Vdd
Vss
J13
Vdd
Vss
J12
Vdd
Vss
J11
Vdd
Vss
J1
J2
1
2
JP3
Vss
J6
6 5 4 3 2 1 . 1
SA2002D
Figure 2: Jumper schematic, digital IO's
Name
Function Description
J1
J1 is used to select the energy direction ( DIRI pin). The three options available are:
P18 connected to Vdd - Negative energy measurement
P18 connected to Vss - Positive energy measurement
P18 connected to J2 (P17) - Bi-directional energy measurement
P18 should not be left floating and must be connected to one of the options described above.
J2
J2 is only used to select bi-directional energy measurement when connected to P18
J3 and J4
These are test points placed next to the digital pins of the SA2002E
J5
Not fitted This is the current sense input ground. If a current transformer is used for current sensing the two
pins of J5 must be connected.
J6
Connects the impulse to VSS. If a stepper motor is connected to JP3 then J6 should be left open.
J7
Analog ground test point (see figure 1)
J8
Positive supply test point (Vdd) (see figure 1)
J9
Negative supply test point (Vss) (see figure 1)
J11, J12
and J13
Used to select the R2, R1 and R0 pins of the SA2002D for the various rated conditions. Refer to table 1 for the
possible settings
J14
Used to select fast calibration mode. Connecting P7 to Vdd selects fast calibration mode. For normal operation
P7 must be connected to Vss
J15
Used to select between normal and configure / test modes. For normal operation connect P9 to Vss.
J16
Used to select between 220V and 110V mains systems (See figure 3). Leave open for 220V mains.
Table 3: Jumper settings for various device options
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ANALOG SECTION
The analog (metering) interface described in this section is
designed for measuring 220V/80A with precision better than
Class 1.
The most important external components for the SA2002D
integrated circuit are the current sense resistors, the voltage
sense resistors and the bias setting resistor. The resistors
used in the metering section should be of the same type so
temperature effects are minimized.
Voltage Input IVP
The voltage input of the SA2002D (IVP) is driven with a current
of 14A at nominal mains voltage. This voltage input saturates
at approximately 17A. At a nominal voltage current of 14A
allows for 20% overdriving. The mains voltage is divided with a
voltage divider to 14V that is fed to the voltage input pins via a
1MW resistor
Voltage Divider
The voltage divider is (Figure 3) calculated for a voltage drop of
14V. Treat C7 as a short circuit and ignore J16. Equations for
the voltage divider in figure 3 are:
RB = R1 + R2 + R3 + R15 + R10
RB = R12 || ( R11 + P1 / 2)
Combining the two equations gives:
(RA + RB) / 220V = RB / 14V
Values for resistors R10 = 47W, R11 = 22kW, P1=10kW and
R12 = 1MW is chosen.
Substituting the values result in:
RB = 26.29kW
RA = RB x (220V / 14V - 1)
RA = 386.84kW
Figure 3: Mains voltage divider
R1
R2
R3
R10
R11
R12
NEUTRAL
C7
R15
J16
P1
LIVE IN
Standard resistor values of R1, R2, R3 and R15 are chosen to
be 47kW, 150kW, 47kW and 150kW. The resistor RA is divided
so that the voltage drop across one resistor is within the
specified limits of the resistor type that is used, usually
200VDC. The resistor value ratios are chosen so that shorting
J16 the module could be used on a 110VAC mains system.
CURRENT SENSOR INPUT RESISTORS FIGURE 4 (USING
A SHUNT RESISTOR)
The resistors R6, R7 define the current level into the current
sense inputs the device. The voltage drop across the shunt
should be at least 20mV at rated conditions. A shunt resistor
with a value of 50mV @80A was chosen for the application
module for its ease of use. The resistor values are calculated
for an input current of 16A on the current inputs at rated
conditions. For a 80A meter the resistor values are calculated
as follows:
R6 = R7 = (I / 16A) x R / 2
L SH
= 80A / 16A x 625uW / 2
= 1.5625kW
I
Line current
L =
A standard value of 1.6kW is chosen.
Figure 4: Current input configuration
R6
R7
R14
LIVE IN
LIVE OUT
L
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CT TERMINATION RESISTOR
Provision is made for the use of a current transformer on the
module. The existing shunt needs to be removed and the
current sense resistors will have to be recalculated for the
specific current transformer. The voltage drop across the CT
termination resistor at rated current should be at least 20mV.
The CT's used should have a low phase shift and a ratio of
1:2500.The CT is terminated with a 2.7W resistor giving a
voltage drop of 864mV across the termination resistor at rated
conditions
CURRENT SENSOR INPUT RESISTORS FIGURE 5 (USING
A CURRENT TRANSFORMER)
The resistors R6, R7 define the current level into the current
sense inputs the device. The resistor values are selected for
an input current of 16A on the current inputs at rated
conditions. For an 80A-rated meter the resistor values are
calculated as follows:
R6 = R7 = (I / 16A) x R / 2
L SH
= 80A / 16A x 2.7W / 2
= 2.7kW
I Line current
L =
RSH = CT Termination resistor
2500 = CT ratio
Figure 5: Current input configuration
LIVE IN
LIVE OUT
R16
IIN
IIP
J5
L
CT1
R6
R7
Phase Compensation (When using a current transformer)
Phase shift caused by the current transformer may be
corrected by inserting a capacitor in the voltage divider circuit.
See Figure 6, Capacitor C7. To compensate for a phase shift of
0.18 degrees the capacitor value is calculated as follows:
C = 1 / (2 x
p
x Mains frequency x R5 x tan (Phase shift angle))
C = 1 / (2 x
p
x 50 x 1M x tan( 0.18 degrees))
C = 1.013F
Reference Voltage VREF
The VREF pin of the SA2002D is connected to a resistor that
determines the on chip bias current.
Ground GND
The GND pin of the SA2002D is to the live phase, which is
halfway between VDD and VSS. Note that supply bypass
capacitors C1 and C2 are positioned as close as possible to the
supply pins of the device, and connected to a solid ground
plane.
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PM2002DP
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Symbol
Description
Detail
SA2002D
Diode, Silicon, 1N4007
Resistor, 47k, 1/4W, 1%, metal
Resistor, 150k, 1/4W, 1%, metal
Resistor, 100R, 1/4W, 1%, metal
Resistor, 1.6k, 1/4W, 1%, metal
Resistor, 2.4k, 1/4W, 1%, metal
Resistor, 47R, 2W, 5%, wire wound
Resistor, 22k, 1/4W, 1%, metal
Resistor, 1M, 1/4W, 1%, metal
Resistor, 24k, 1/4W, 1%, metal
Shunt resistor, 80A / 50mV
Resistor, 1/4W, 1%, metal
Capacitor, 220nF
Capacitor, 220nF, 16V, electrolytic
Capacitor, 470nF, 250VAC
Capacitor, 820nF
Capacitor
Capacitor, 2200uF, 16V, electrolytic
3mm Light emitting diode
Impulse counter, Kuebler, K07.80
Molex 3 pin connector, 200mil pin spacing
Molex 2 pin connector, 100mil pin spacing
Jumpers
Header pins
U1
D1, D2
R1, R3
DIP-20
R2, R15
R4, R5
R6, R7
R8, R9
R10
R11
R12
R13
R14
R16
P1
C1, C2
C3, C4
C5
C6
C7
C8
LED1, LED2
CNT1
SCK1
JP3
6
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COMPONENT LISTS
The following component list covers all components fitted on the PM2002DP module as shipped
Diode, Zener, 2.4V
D3, D4
Resistor, 1/4W, 1%, metal
Note 1
Note 1
Note 2
Note1: In case a current transformer is used on the board R16 is the termination resistor. Resistors R6 and R7 values may need to be
changed to match the CT used.
Note2: Capacitor values may be selected to compensate for phase errors caused by current transformers.
Table 4: Components for PM200DP module set up for 220V/80A
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