IM3318

Three-Phase Energy Metering Module

Product Series

Product Series	Temperature Range	Operating Voltage	Package
IM3318	-40℃～+85℃	3.3VDC	SMD18

Product Features:

• Single input power supply
• High precision electrical parameter measurement
• Provides AC voltage, current, power, power factor, frequency and other parameters
• Baud rate support 1200-9600kbps Default: 2400, even parity
• Provides voltage loss detection, voltage and current reverse phase sequence detection
• Provides Modbus protocol
• User-friendly, low product development cost

Product Applications:

• Motor protection
• Coal mining industry
• Power monitoring
• Petroleum and chemical industry
• Building automation
• Fire power supply monitoring

Product Model

Product Model	Power Supply Voltage (Range) (VDC)	Quiescent Current (mA)	Default Baud Rate (kbps)	Parity Check Type	Default Modbus Address	Communication Interface
IM3318	3.3 (3.15-3.45)	35	2400	Even Parity	01	TTL

Input Characteristics

Parameter	Condition	Minimum Value	Typical Value	Maximum Value	Unit
Input Voltage	3.3VDC Input Series	3.15	3.30	3.45	VDC
	5VDC Input Series	4.75	5.00	5.25	VDC
Drive Current	TXD, RXD	--	--	2	mA
	CON	--	--	5	mA
Serial Interface	3.3VDC Input Series	Only compatible with +3.3V standard UART interface
	5VDC Input Series	Only compatible with +5V standard UART interface

Analog Signal Characteristics

Parameter	Condition	Minimum Value	Typical Value	Maximum Value	Unit
Voltage Sampling Signal	--	7	--	265	VAC
Current Sampling Signal	--	0	--	5	A

Pin Definition

Pin Number	Pin Name	Characteristic	Function Description
1	VCC	Input	Module power supply pin. Operating voltage: 3.3V. This pin can be connected to 10UF/16V capacitor in parallel with 100NF/16V ceramic capacitor for decoupling
2	GND	Reference Ground	Digital power ground
3	RXD	Input	UART communication receive data pin, TTL level interface. Can be directly connected to user MCU UART
4	TXD	Output	UART communication transmit data pin, TTL level interface. Can be directly connected to user MCU UART
5	RD	Output	Currently not supported
7,9,11	NC	None	No connection. Recommended: leave floating
6	VN	Input	Voltage channel neutral line input port, can directly connect neutral line to pin
8	VA	Input	Voltage channel Phase A sampling input port. Direct three-phase Phase A
10	VB	Input	Voltage channel Phase B sampling input port. Direct three-phase Phase B
12	VC	Input	Voltage channel Phase C sampling input port. Direct three-phase Phase C
13	IC-	Input	Current channel Phase C negative current signal input terminal, port Imax 5A. Recommended circuit: Connect CT with ratio of 1000A/5A or below according to user load
14	IC+	Input	Current channel Phase C positive current signal input terminal, port Imax 5A. Recommended circuit: Connect CT with ratio of 1000A/5A or below according to user load
15	IB-	Input	Current channel Phase B negative current signal input terminal, port Imax 5A. Recommended circuit: Connect CT with ratio of 1000A/5A or below according to user load
16	IB+	Input	Current channel Phase B positive current signal input terminal, port Imax 5A. Recommended circuit: Connect CT with ratio of 1000A/5A or below according to user load
17	IA-	Input	Current channel Phase A negative current signal input terminal, port Imax 5A. Recommended circuit: Connect CT with ratio of 1000A/5A or below according to user load
18	IA+	Input	Current channel Phase A positive current signal input terminal, port Imax 5A. Recommended circuit: Connect CT with ratio of 1000A/5A or below according to user load

As shown in the figure, there are four wiring methods for IM3318: three-phase three-wire, three-phase four-wire, direct connection, and CT (Current Transformer) connection. The module wiring method is simple and reliable, convenient for users.

Note:

• Three-phase three-wire connection: Phase B of the voltage sampling circuit should be connected to the UN terminal of IM3318. IB current can be left floating.
• Direct connection allows a maximum current load of 5A. For loads exceeding 5A, use CT connection with external CT with secondary rated at 5A (50A/5A, 100A/5A, 200A/5A, 300A/5A, 1000A/5A, etc.). The current ratio can be set up to 200, with maximum testing capacity of 1000A current load.

Software Application Protocol

IM3318 supports Modbus-RTU protocol. For detailed protocol content, please refer to: MODBUS Protocol Description

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Usage Precautions

1. The firmware and protocol of IM3318 are built-in at the factory, making it convenient for users.
2. When testing with IM3318, since the module measures high voltage equipment, pay attention to operation safety to avoid damaging the module and computer. The recommended schematic design includes communication isolation circuit for user reference.
3. When testing Modbus protocol with IM3318, users can use our provided test software.
4. Disclaimer: The information in this document is for reference only and does not constitute any invitation or commitment. iReader may modify the above information without prior notice.

Three-Phase Energy Collection Module Protocol Description

Meter Information and Parameter Setting Register Area

Address	Parameter	Value Range	Data Type	Read/Write Property
0000H	Module Information	High byte: Module model Low byte: Software version	Word	R
0001H	Basic Range	High byte: Basic voltage Low byte: Basic current	Word	R
0002H	Module Working Information	High byte: Module address Low byte: Baud rate *1	Word	R/W
0003H	Current Ratio IBB	BCD code, Maximum setting 9999 times Default: 1 time	Word	R/W
0004H	Voltage Ratio UBB	BCD code, Maximum setting 9999 times Default: 1 time	Word	R/W
0005H	Energy Reset	High byte: Energy reset Low byte: Meter initialization *2	Word	R/W
0006H	Electrical Working Status	Total 12 status *3	Word	R
0007H	Protocol	Tongliao Protocol: 5555 Other: AAAA	Word	R/W
0008H	Input Detection	High byte: 0x00 Low byte: Two-way detection *4	Word	R
0009H	Parity Bit	High byte: 0x00 Low byte: Parity selection *5	Word	R/W
000AH	Wiring Method	High byte: 0x00 Low byte: Wiring method selection *6	Word	R/W

Notes:

*1 Baud Rate:

• 0x04: 1200
• 0x08: 2400
• 0x10: 4800
• 0x20: 9600
• Other values: 2400

*2 Set 0xAA: Clear related information

*3 Status Bit Definitions:

Bit	Description
BIT00	1: Phase A voltage loss | 0: Phase A voltage normal
BIT01	1: Phase B voltage loss | 0: Phase B voltage normal
BIT02	1: Phase C voltage loss | 0: Phase C voltage normal
BIT03	1: Voltage reverse phase sequence error | 0: Voltage phase sequence normal
BIT04	1: Current reverse phase sequence error | 0: Current phase sequence normal
BIT05	1: At least one phase active power is negative | 0: All active power is positive
BIT06	1: At least one phase reactive power is negative | 0: All reactive power is positive
BIT07	Undefined
BIT08	Undefined
BIT09	1: Phase A in creep state | 0: Phase A in start state
BIT10	1: Phase B in creep state | 0: Phase B in start state
BIT11	1: Phase C in creep state | 0: Phase C in start state
BIT12	1: Combined phase active power is negative | 0: Combined phase active power is positive
BIT13	1: Combined phase reactive power is negative | 0: Combined phase reactive power is positive
BIT14	Undefined
BIT15	Undefined

*4 Low byte bits 0 and 1 indicate input detection status. Example: 0x01 (0000 0001): Indicates first channel has data.

*5 Low byte: Parity selection

• 0x01: Odd parity
• 0x02: Even parity
• 0x03: No parity
• Default: 0x02

*6 Low byte: Wiring method selection

• 0x55: Three-phase four-wire
• 0xAA: Three-phase three-wire

Electrical Parameter Register Area<td style="border: 1px solid #dd

Address	Parameter	Value Range	Data Type	Read/Write Property
0020H (High 16 bits)	Total Active Energy	0--999999.99Kwh	Dword	R
0021H (Low 16 bits)
0022H (High 16 bits)	Total Reactive Energy	0--999999.99Kvar	Dword	R
0023H (Low 16 bits)
0024H (High 16 bits)	Total Active Power	0-9999.9999KW	Dword	R
0025H (Low 16 bits)
0026H (High 16 bits)	Total Reactive Power	0-9999.9999KVar	Dword	R
0027H (Low 16 bits)
0028H (High 16 bits)	Phase A Active Energy	0--999999.99Kwh	Dword	R
0029H (Low 16 bits)
002AH (High 16 bits)	Phase A Reactive Energy	0--999999.99Kvar	Dword	R
002BH (Low 16 bits)
002CH	Phase A Voltage	0-999.9V	Word	R
002DH (High 16 bits)	Phase A Current	0-99999.999A	Dword	R
002EH (Low 16 bits)
002FH (High 16 bits)	Phase A Active Power	0-9999.9999KW	Dword	R
0030H (Low 16 bits)
0031H (High 16 bits)	Phase A Reactive Power	0-9999.9999KVar	Dword	R
0032H (Low 16 bits)
0033H	Phase A Power Factor	0-1.000	Word	R
0034H (High 16 bits)	Phase B Active Energy	0--999999.99Kwh	Dword	R
0035H (Low 16 bits)
0036H (High 16 bits)	Phase B Reactive Energy	0--999999.99Kvar	Dword	R
0037H (Low 16 bits)
0038H	Phase B Voltage	0-999.9V	Word	R
0039H (High 16 bits)	Phase B Current	0-99999.999A	Dword	R
003AH (Low 16 bits)
003BH (High 16 bits)	Phase B Active Power	0-9999.9999KW	Dword	R
003CH (Low 16 bits)
003DH (High 16 bits)	Phase B Reactive Power	0-9999.9999KVar	Dword	R
003EH (Low 16 bits)
003FH	Phase B Power Factor	0-1.000	Word	R

C Phase Electrical Parameters

Address	Parameter	Value Range	Data Type	R/W Attribute
0040H (High sixteen bits)	C Phase Active Energy	0-999999.99 Kwh	Dword	R
0041H (Low sixteen bits)			Dword	R
0042H (High sixteen bits)	C Phase Reactive Energy	0-999999.99 Kvr	Dword	R
0043H (Low sixteen bits)			Dword	R
0044H	C Phase Voltage	0-999.9 V	Word	R
0045H (High sixteen bits)	C Phase Current	0-99999.999 A	Dword	R
0046H (Low sixteen bits)			Dword	R
0047H (High sixteen bits)	C Phase Active Power	0-9999.9999 KW	Dword	R
0048H (Low sixteen bits)			Dword	R
0049H (High sixteen bits)	C Phase Reactive Power	0-9999.9999 KVar	Dword	R
004AH (Low sixteen bits)			Dword	R
004BH	C Phase Power Factor	0-1.000	Word	R
004CH	Grid Frequency	0-99.99 Hz	Word	R

Control Output Register Area

Address	Parameter	Value Range	Data Type	R/W Attribute
0000H	FF00: Output 1 0000: Output 0		Word	W
0001H	FF00: Output 1 0000: Output 0		Word	W
0002H	FF00: Output 1 0000: Output 0		Word	W

User Setting EEPROM Register Area

Address	Parameter	Value Range	Data Type	R/W Attribute
0000H	0X00-0XFF		BYTE	R/W
...	0X00-0XFF		BYTE	R/W
0010H	0X00-0XFF		BYTE	R/W

MODBUS Protocol Overview

This protocol uses a master-slave structure and half-duplex communication mode. Slave stations have their own address codes. The establishment and release of the communication link are both controlled by data frames sent from the master station.

1. Function Code "03": Read Multiple Registers
Master transmission message format:

Master Transmission	Byte Count	Information Sent	Remarks
Slave Address	1	01	Sent to slave with address 01
Function Code	1	03	Read Registers
Start Address	2	0020	Start address is 0020
Data Length	2	0002	Read 2 registers (4 bytes total)
CRC Code	2	C5C1	CRC code calculated by master

Slave response message format:

Slave Response	Byte Count	Returned Information	Remarks
Slave Address	1	01	From slave 01
Function Code	1	03	Read Registers
Byte Count	1	04	2 registers total 4 bytes
Register Data 1	2	0000	Content of address 0020
Register Data 2	2	0010	Content of address 0021
CRC Code	2	FBF5	CRC code calculated by slave

 

Product Datasheet
IM3318

Data Sheet
Three-Phase Energy Metering Module

2. Function Code "06": Write Single Register
Master transmission message format:

Master Transmission	Byte Count	Information Sent	Example
Slave Address	1	01	Sent to slave with address 01
Function Code	1	06	Write Single Register
Start Address	2	0002	Register address to write to
Write Data	2	0108	Corresponding new data
CRC Code	2	28C5	CRC code calculated by master

Slave (PDM) response message format:
Identical to the message format and data content sent by the master.

MODBUS Protocol Examples

1. Set Module Address, Baud Rate
Master transmission data:
01 06 00 02 01 08 28 5C
01: Module address
06: Protocol function code
00 02: Setting register address
01 08: Setting data 01: Set address 08: Set baud rate (Refer to meter information and parameter settings for specific data)
08 5C: Data CRC check
Return data: 01 06 00 02 01 08 28 5C

2. Set Module Current Transformer Ratio
Master transmission data:
01 06 00 03 00 70 78 2E
01: Module address
06: Protocol function code
00 03: Setting register address
00 70: Setting data 0070: Indicates setting current transformer ratio to 70 times (BCD code) 01 00: Indicates 100 times
08 5C: Data CRC check
Return data: 01 06 00 03 00 70 78 2E

3. Read Module Total Active Energy
01 03 00 20 00 02 C5 C1
01: Module address
03: Protocol function code
00 20: Read register address
00 02: Number of module registers to read
C5 C1: Data CRC check
Return: 01 03 04 00 00 00 08 FB F5
01: Module address
03: Protocol function code
04: Number of register data bytes read (number of registers * 2)
00 00 00 08: Module register data read Indicates: Active energy 000000.08 Kwh
FB F5: Data CRC check

Note:
All data read is in BCD code format.
00 00 00 08 indicates: 000000.08
For example: If the voltage data read is 0x22 0x01, it indicates a voltage value of: 220.1V

4. Set User EEPROM Data
Transmit:
AA F6 00 00 10 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 5E 4D

AA: Module address
F6: Protocol function code
00 00: Setting register address
00 10: Setting data length
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F: Setting data
5E 4D: Data CRC check

Receive:
AA F6 00 00 10 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 5E 4D

5. Read User EEPROM Data
Transmit:
AA F3 00 00 10 1D C8
AA: Module address
F3: Protocol function code
00 00: Read register address
00 10: Read data length
1D C8: Data CRC check

Receive:
AA F3 10 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F D9 41
AA: Module address
F3: Protocol function code
00 00: Read register address
00 10: Read data length
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F: Read data
D9 41: Data CRC check

6. Set Relay Output Data
Transmit:
01 05 00 00 FF 00 8C 3A

01: Module address
05: Protocol function code
00 00: Control relay register address
FF 00: Function code (FF00: Output 1 0000: Output 0)
8C 3A: Data CRC check

Receive:
01 05 00 00 FF 00 8C 3A

Appendix:
Gain Calibration (Module parameters at 220V, 2.5A, Power Factor 1.000)
Transmit:
AA 7A 22 00 22 00 22 00 25 00 25 00 25 00 05 50 05 50 68 F4
01: AA: Module address
7A: Protocol function code
22 00 22 00 22 00: Calibration voltage for A, B, C phases respectively (22 00: indicates 220.0V)
25 00 25 00 25 00: Calibration current for A, B, C phases respectively (25 00: indicates 2.500A)
05 50 05 50 05 50: Calibration active power for A, B, C phases respectively (05 50: indicates 0.550KW)
68 F4: Data CRC check

Receive:
AA 7A 22 00 22 00 22 00 25 00 25 00 25 00 05 50 05 50 68 F4

Phase Calibration (Module parameters at 220V, 2.5A, Power Factor 0.500L)
Transmit:
AA 9A 22 00 22 00 22 00 25 00 25 00 25 00 02 75 02 75 02 75 40 06
01: AA: Module address
9A: Protocol function code
22 00 22 00 22 00: Calibration voltage for A, B, C phases respectively (22 00: indicates 220.0V)
25 00 25 00 25 00: Calibration current for A, B, C phases respectively (25 00: indicates 2.500A)
05 50 05 50 05 50: Calibration active power for A, B, C phases respectively (05 50: indicates 0.550KW)
40 06: Data CRC check

Receive:
AA 9A 22 00 22 00 22 00 25 00 25 00 25 00 02 75 02 75 02 75 40 06