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PDF PM9904BPD Data sheet ( Hoja de datos )
| Número de pieza | PM9904BPD | |
| Descripción | Evaluation Board | |
| Fabricantes | Sames | |
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Evaluation Board for the SA9904B Energy
Metering IC
PM9904BPD
sames
FEATURES
+ Designed to be used together with accompanying
software as fully functional three phase trivector meter.
+ Better than class 1 operation.
+ On board power supply.
+ Two on-board LED’s for active and reactive pulse output.
+ 3 Phase 4 wire configuration.
+ On-board LCD display.
+ On-board current transformers.
+ Isolated connection to PC parallel port.
+ Easy accessible test pins.
+ Micro-controller plug-in support
DESCRIPTION
This application note describes the PM9904BPD evaluation
board and together with the SA9904B data sheet provides a
complete evaluation platform. The SA9904B is an accurate bi-
directional power / energy measurement IC with serial (SPI)
interface measuring active as well as reactive power / energy,
RMS voltage and frequency. More detailed information
specific to the of SA9904B can be found in its datasheet.
The PM9904BPD module is designed for a three-phase four-
wire applications, referenced to neutral. The mains voltages
easily connect to module by way of a Molex connector (SK1).
The 3 on-board current transformers measures the current in
each phase. A simple capacitive power supply supplies the
energy metering IC with power. The LM431 regulators are
used to generate a 5 V supply voltage for the on-board opto-
couplers. Provision has been made to connect an external 5V
power supply to drive the isolated opto-coupler.
The SA9904B forms the energy/power metering front-end of
the module and connects to the SPI bus. Sharing the SPI bus
is the SA8807A LCD driver which is capable of driving 96
segments on a 4 back plane LCD.
The PM9904BPD evaluation board is configured and
calibrated via the parallel port of a PC. The data interface
between the evaluation board and the PC is fully isolated.
The PM9904BPD module can easily be connected to a micro-
controller. The SAMES micro-controller board connects to the
evaluation module by means of JP1 thereby creating a
complete power meter without the PC interface. Physically the
micro-controller board plugs into the evaluation module with its
opto-coupler facing the mains connector (SK1). It shares the
SPI bus with the SA8807A onboard LCD controller.
SK1
GND
Power
Supply
VDD
GND
VSS
LCD
DISPLAY
PCVSS
JP4
PCVDD
SK3
VDD PCVDD
PCVSS
CT1 Resistor
Network
CT2 Resistor
Network
CT3 Resistor
Network
SPEC-0448 (REV. 6)
SA8807A
SA9904A
JP1
F50
J12
Test Pins VDD
Figure 1: Block diagram
1/22
VSS PCVSS
JP2
JP3 PCVSS
Test Pins
19-06-02
1 page  
PM9904BPD
sames
where:
Vnom is the mains voltage and correspond to 14µA in the
voltage inputs of the SA9904B.
Imax is the maximum mains current to be measured and
correspond to 16µA on the current inputs of the SA9904B.
The pulse rate required for a meter is usually expressed in
pulses/kWh. A single pulse on the LED is mostly a fraction of a
kWh and is converted to energy in Ws/pulse
Energy per LED pulse is (Ws/pulse):
Epp energy = 1000 x 3600 / Mpr
where:
Epp is energy per LED pulse
Mpr is the meter pulse rate or meter constant in pulses/kWh
The threshold is calculated by dividing the energy represented
by a LED pulse by the energy per register count.
Active energy threshold = Epp / Epc
The threshold is thus the amount of energy to be measured
(accumulated / integrated) by the meter before a LED pulse is
generated.
Pulse threshold
Threshold value subtracted
from integrator
The simplest way to implement the creep threshold is to relate
it to the time between meter pulses. If the time between pulses
is more than the limit, the energy accumulator is cleared.
Pulse rate of meter at rated conditions (Hz):
Rf = ( Vnom x Imax / 1000 ) x ( Mpr / 3600 )
where:
Vnom is the mains voltage and correspond to 14µA in the
voltage inputs.
Imax is the maximum mains current to be measured and
correspond to 16µA on the current inputs of the device.
Mpr is the meter pulse rate in pulses/kWh.
Creep threshold time (s):
Ct = 1/(Cc / Imax) x Rf
where:
Cc is the specified creep current; energy below this value is
discarded.
Imax is the maximum mains current to be measured and
correspond to 16µA on the current inputs of the device.
Rf is the rated current frequency.
The flow diagram (figure 6) for the timer interrupt shows how
the time between pulses is measured, if the time since the last
pulse is more than the time measured, the integrator is reset
and a new count down is started.
Start Timer Interrupt
Integrator zero
Pulse LED
Reg 8 add to Integrator
Reg 4 add to Integrator
Reg 0 add to Integrator
Pulse Generated
Figure 5: Implementation of an overflow integrator
Meter creep current
For the SA9904B meter creep must be taken care of in
software. From the explanation above on how to generate
pulses, the meter must also be prevented from pulsing in
cases where the energy measured is less than the creep
threshold as per the meter specification. The creep current is
defined as the limit for measured energy, any energy less than
the creep threshold is discarded, and energy above the creep
threshold is measured.
No
No
http://www.sames.co.za
5/22
If LED On
Yes
Decrement LED ON timer
If LED ON Timer = 0
Yes
Switch LED off
If creep timer > 0
Yes
Decrement creep timer
If creep timer = 0
No
Exit Interrupt
Yes
Load creep timer
Reset integrator
Figure 6: Interrupt flow diagram
5 Page 
PM9904BPD
THE LIQUID CRYSTAL DISPLAY
sames
0.2
Figure 13: All the Icons and Dimensions of LCD
Pin 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22
COM1 cosf 1f 2f 3f 4f 5f 6f 7f 8f %Error
COM2 Total 1g 2g 3g 4g
5g 6g 7g 8g
imp/KWh
COM3 Com 1e 2e 3e 4e
5e 6e 7e 8e
Wh/imp
COM4 Cost 1d 2d 3d 4d T1 5d T2 6d T3 7d T4 8d Total ~ 3
Table 3 : Mapping of display
Pin
COM1
COM2
COM3
COM4
1
T1
T2
T3
T4
2 3 4 5 6 7 8 9 10 11 12 13 14
1a 2a 3a 4a 5a 6a 7a 8a
1b 2b 3b 4b 5b 6b 7b 8b
1c 2c 3c 4c 5c 6c 7c 8c
1h 2h 3h 4h 5h 6h 7h 8h
Table 4 : Mapping of display (continued)
15
V
A
r
h
21 23 23
k1
Hz
~ 1 COM3
~ 2 COM4
16 17 18
k2 COM1
W COM2
s
h
http://www.sames.co.za
11/22
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