1. Introduction
Single phase electric meter DDSY150-SSK  is a new type of electric meter having the prepayment function. The user can purchases energy from the vending network by getting the serial number ( named as " TOKEN"), which could be entered via keypad to load the pre-purchased energy. The TOKEN contains 20 digits which are encrypted. Because the activity of recharging is realized by keypad, this meter is named as " Keypad Meter". This meter is equipped with infrared communication port, double metering sensors, double control switches, real time clock unit, and other auxiliaries.
 
The data transmissions protocol of DDSYXXXX complies with IEC62055-41 and IEC62056-21. All the specifications and performance index comply with IEC62053-21 regulations to Class 1.0 Static Meters for Active Energy.
 
 
2. Functions and features:
A. Active energy measurement;
B. Adopt 20-digit token as data transmission media, you can purchase energy before consumption;
C. Double loop measurement both on neutral and phase lines,
D. Accumulate the total energy with unit of 0.01 kWh;
E. Display the real-time current and voltage;
F. LCD display with backlight
G. Low energy alarm to remind you to purchase energy;
H. Double relays to control the neutral and phase circuits;
I. Infrared communication for data transmission and parameter settings
J. Event record function (including cover opening event, tamper event and power failure event, etc.)
K. Ground line connection design;
L. Anti-tampering features( including opening terminal cover, short circuited, current injection, reverse wiring, magnetic disturbance, etc.)
 
3. Meter specifications
 

 
 
 
4.3 LED indicator
LED from left  to right in sequence are indicating
-Pulse (RED color);
-Power supply and credit status(bi-color, normal status in GREEN, low credit status in RED and blinks);
--Alarm / Tampering (YELLOW color);
4.4 Keypad
Contains the keys of number from 0-9 and symbol "←" and "",used for input, cancel, confirm, and check the TOKEN.
4.5 Communication port
Optical communication port complies with IEC 62056-21 /IEC 61107 protocol.
4.6 Terminal cover detector used for detecting the terminal cover open status.
 
5. Operation principle
As shown in Figure 5, the incoming current and voltage are input into the special energy measurement IC via separate sampling circuit, measuring chip exports the impulse signal by a ratio of measured power to microprocessor ( MCU ), MCU calculates and processes the impulse and perform the energy metering and load control functions etc. Because of bi-loop measurement, the energy is sampling from both phase line and neutral line, the MCU could read the real-time current, voltage, detect the real-time energy consumption status, and process the tampering condition. LED indicate the impulse, power/ credit status, alarm, to show the meter working status. Meter has high-precision clock and super capacitor ensure the meter could work at least for 48 hours when power off.

6. Meter application
 
6.1 Purchase energy
Prepayment power vending management system will produce a 20 digits code (generated based on user's information and purchasing amount). You need to input this code to the meter with keypad. The meter will decrypt the code and write the purchased energy into the meter and will also add the energy into the balance energy and then save it. When the overdraft and abnormal power consumption occurred, the meter will deduct this consumption first and then the meter will save the balance energy into the meter. When you use the energy, the meter will deduct the balance energy according to relevant condition. The meter can power off the energy automatically when meter meets the condition of disconnection. The meter can recover to supply energy automatically when the meter meets the condition of recovery energy.
 
When the balance energy is low, you can go to the vending station of the utility to purchase electricity. The operator will give the user a 20 digits token according to user's information and quantity the user purchased.
 
Power purchase steps:

• go to local power supply bureau
• provide your meter ID to the operator
• inform operator the quantities you want to buy
• obtain a 20 digits token printed on your receipt.

 
6.2 Input energy
You will input the code through meter's keypad to load the energy purchased. After encryption key verification, meter will accept energy and adjust the residual amount and accumulative power-purchasing amount and then save the final residual amount into EEPROM. At the same time power amount loaded this time will also be displayed on LCD.
Input the token into meter steps:

• Input 20 digits token via keypad of the meter
• confirm the code from LCD
• If token is wrongly inputted, please use backspace to modify.
• If the token is correctly inputted, press " " to confirm the token.
• if token is correct, LCD will display "BENAR" and the energy you purchased.
• If token is incorrect, the LCD will display "GAGAL".

 
6.3 Token information
TOKEN code is composed by 20 digits, which should be entered via keypad. The meter sounds "Ding" when pressing the buttons of keypad. The sequence of number entering will starting from right hand side, and the last number entered will be shown on most right hand side of text display area. The LCD will show the digits entered, and also the number of digit. When you enters the 8^th digit, the 1^st digit will be moved to the display area. Please see more details as follows.
 
 
 
  After entering all 20 digits of TOKEN, press "" button to confirm and submit. If the TOKEN is correct and accepted, meter would display text of " BENAR" and buzz " Ding" for twice. If the TOKEN is incorrect and rejected, meter would display text of " GAGAL" or SErr information and buzz for 3 times.  
When TOKEN is incorrect and rejected, meter will display as follows.
   
 
 
 7. Display function
The  meter has 3 display modes of automatic display, manual querying display and power down display. Meter starts automatic display of balance energy value and error information when power is on. When it is in automatic display mode, the screen starts with balance enegy and slipps for every 5 seconds. The backlight will be ON and lasts for 15 seconds for pressing keypad, 10 seconds for pressing program button.  
7.1  Automatic display
Meter will display the balanced energy and error information as follows in automatic display mode.
   
7. 2 Power down display
Meter will display the following contents when power down.
   
7. 3 Mannual querying Display
When you press the code numbers and key of "", the meter will display corresponding data contents as following examples.
If the data code is reserved or correct, then " 0.0 " will be displayed.
   
Data code details for manual querying:
 

 
 
 
8.  Alarm function
8.1 Low balance alarm
To remind the customer to purchase balance in time, meter has two level low balance alarm and it can be set.
Level 1: Green LED will flash and buzzing. This alarm can be canceled after pressing any button , but the alarm will come again without entering TOKEN.
Level 2: Buzzing duration is shorter than level 1.
Remark: All the "alarm duration" and "low balance threshold" can be set through entering the technical code of "123***" (*** is minutes) .
 
8.2 Relay trip alarm
When you install the meter, the duration exceeds limitation of 45 seconds, the relay will switch off, yellow LED will be on and buzzing. After 150 seconds, the meter will switch on again automatically.
If the meter in overload condition accumulative exceeds 45 seconds in 30 minutes, the relay will switch off , but will switch on again after 150 seconds.
The delay time can be adjust by computer.
If the meter cover is opened, the relay would trip off with flashing "Alarm" LED, buzzing and indicator of tampering.
The status of switch off could be canceled through enter the TOKEN "INPUNTED"
If the power line is reversely connected, meter could measure as normal. But when balance energy is run out, meter will not accept any new TOKEN until it resume to "REPAIRED".
 
 
9.  Communication
Infrared communication port is comply with IEC61107.