EMA-1 disassembly/technical - 3 battery version

There are two common versions of the EMA-1. There are major internal differences between the two versions. The version examined on this page uses three button cell batteries. The two battery version is examined here.

There is no point taking the device apart. There are no user serviceable parts inside. You do not need to take the device apart to replace the batteries. See the battery replacement section on the updated instructions page.

Case front with display, controls, appliance socket

Buttons are: MASTER CLEAR (in recess), UP, SET, FUNC

Back panel:

Text on back panel:

 Type  EMA-1 CS 07442V
 Voltage  230-240V~50Hz
 Max. load
 10 A,2400 W
 Measurable current
 0.01 A - 10 A
 Line voltage display
 200 V~ -276 V~
 Wattage  0.2 W - 2760 W
 kWh display
 0.0 kWh - 9999.9 kWh
 Battery  3X1.5V AG13/LR44

Note: The model number chosen by the manufacturer is identical to the earlier Type 1 Meter  - even though this Type 2 meter is substantially different.

AC & Logic board

Logic front view:

The phase circuit enters the phase pin, passes through the main board and a 2 ohm shunt solid wire resistor, and then back out to the phase socket. The earth pin/socket and neutral pin/socket are pass through.

Logic rear view closeup of the above board:

The logic board contains two easily identifiable chips on the rear:

1. Cirrus Logic CS5460C-ISZ single chip metering (press release, description, datasheet)
2. K24C02 two wire serial eeprom 2K 256 x 8 (example datasheet)

The metering chip is on the far left of the picture. The EEPROM is on the right above.

Display board

Display board.

There is micro momentary press switch positioned between two screws on the far left of the board. The function of this switch is unknown.

Display board reverse side. The symbol on the right hand side corresponds to the momentary switch position above.

Discuss technical / disassembly

[in progress]