Carlo Gavazzi ET340

Compatibility

Compatible with EpiSensor Edge over Modbus RTU

The ET340 is compatible with EpiSensor Edge over its RS-485 Modbus RTU port, read through a ZMB-31 Modbus Interface or a Gateway serial port. Carlo Gavazzi publishes the register map with physical addresses, data types, word order and scaling for read functions 03 and 04.

ET340-DIN AV2 3 X S1 X, using the EM300/ET300 communication protocol version 2 revision 17. Site check: read the identification code at 0x000B and expect 345 before adding points. The datasheet documents RS-485 Modbus RTU only, with no Ethernet or Modbus TCP port. Read-only monitoring: no writes to the configuration, serial-port or reset registers.

Connect it with

• Modbus Interface ZMB-3X From €399 ex VAT Configure
• Gateway ZGW-20 From €899 ex VAT Configure

Models

Specifications

The ET340 measures a three-phase load up to 65 A directly, with no current transformers, and powers itself from the measured voltage. It has no display or keys: two LEDs show power, communication and a 1000 pulse per kWh flash, and the measurements are read over Modbus RTU on the RS-485 screw terminals, either RJ45 socket or the front optical port. All of these are the same Modbus port in parallel, so use one at a time.^2, 3

Order code

ET340-DIN AV2 3 X S1 X: range AV2, system 3, self power supply X, output S1 (RS-485 Modbus port), option X (none). S1 is the only output listed.²

Measuring inputs

208 to 400 V L-L AC, 45 to 65 Hz; direct current measurement 5(65) A (Ib 5 A, Imax 65 A, Imin 0.25 A, start-up 20 mA).^2, 3

Systems

Three-phase 4-wire, three-phase 3-wire and two-phase 3-wire.^2, 3

Accuracy

Active energy class 1 (EN 62053-21), reactive energy class 2 (EN 62053-23); current ±0.5% RDG from 0.2 Ib to Imax; phase-neutral voltage ±0.5% RDG, phase-phase ±1% RDG.²

RS-485

Modbus RTU slave on terminals 7 (T), 8 (B+), 9 (A-) and 10 (GND), and two RJ45 sockets (pin 4 B+, pin 5 A-, pin 8 GND). Address 1 to 247 (default 1); 9.6, 19.2, 38.4, 57.6 or 115.2 kbit/s; even or no parity. The protocol gives 9600 bit/s, no parity and 1 stop bit as defaults.^1, 2

Bus

1/8 unit load, up to 247 transceivers on one bus, a repeater beyond 1000 m. Terminate the last device by linking A- (9) to T (7). Data refresh 1 s; 50 words per read request.^2, 3

Digital input

One voltage-free contact on terminals 11 and 12 for tariff selection: open is tariff 1, closed is tariff 2.^2, 3

Supply

Self-powered from the measuring inputs, 208 to 400 V L-L -20% +20%; at most 1 W and 10 VA.²

Approvals

CE; safety EN 62052-11; metrology EN 62053-21.²

Housing

3 DIN modules, 54 × 90 × 63 mm, DIN-rail mounting, sealing covers included. IP20 front and terminals. Measuring terminals 2.5 to 16 mm²; other terminals 1.5 mm².^2, 3

Environment

Operating -20 to +65 °C, 0 to 90% RH non-condensing at 40 °C, indoor; storage -30 to +80 °C. Overvoltage category III.²

Interface

Documented measurements and integration boundaries for ET340.

• Addresses are physical word addresses sent in the frame: L1-N voltage is printed as Modicon 300001 and physical 0000h, and goes on the wire as 0x0000. FC03 and FC04 return the same values.
• INT32 values are two registers, low word first, with each word high byte first. Signed values use two's complement.
• L1-N, L2-N and L3-N voltage at 0x0000, 0x0002 and 0x0004; L1-L2, L2-L3 and L3-L1 at 0x0006, 0x0008 and 0x000A: INT32, volts × 10.
• L1, L2 and L3 current at 0x000C, 0x000E and 0x0010: INT32, amperes × 1000. Neutral current at 0x0098, same format, listed for the ET series and EM330.
• L1 to L3 active power at 0x0012 to 0x0016 (W × 10), apparent power at 0x0018 to 0x001C (VA × 10) and reactive power at 0x001E to 0x0022 (var × 10): INT32.
• System values: V L-N at 0x0024 and V L-L at 0x0026 (V × 10), W at 0x0028, VA at 0x002A and var at 0x002C (× 10), demand W at 0x0038 and peak demand W at 0x003A (W × 10): INT32.
• Power factor L1, L2, L3 and system at 0x002E to 0x0031: one register each, INT16, PF × 1000. A negative value means exported active power.
• Phase sequence at 0x0032 (INT16; the protocol gives 0 as L1-L2-L3 and 1 as L1-L3-L2) and frequency at 0x0033 (INT16, Hz × 10).
• Imported energy: kWh(+) total at 0x0034, kvarh(+) total at 0x0036, partial kWh(+) at 0x003C, kWh(+) per phase at 0x0040 to 0x0044, tariff 1 and tariff 2 at 0x0046 and 0x0048. All INT32, kWh × 10 or kvarh × 10.
• Exported energy: kWh(-) total at 0x004E, kvarh(-) total at 0x0050 and kWh(-) per phase at 0x0060 to 0x0064 (ET series only): INT32, × 10. They count only in measurement mode B.
• Run-hour meter at 0x005A: INT32, hours × 100, ET series and EM330. Rows marked not available in the table (THD, kVAh, tariffs 3 to 8) read 0.
• Identity: identification code at 0x000B (UINT16, 345 for the ET340), firmware version and revision at 0x0302 and 0x0303, serial number as ASCII in the low byte of 0x5000 to 0x5006. Read 0x000B as a single register.
• Configuration from 0x1000, the serial port from 0x2000 and the reset commands from 0x4000 are writable, including a reset of the total energy counters on X-option meters. Keep them out of a monitoring poll.

Setup

1. Identify the transducer

   Read the order code on the side label: ET340-DIN AV2 3 X S1 X. The side label also numbers the RS-485 terminals 7 (T), 8 (B+), 9 (A-) and 10 (GND) and the tariff input 11 and 12.

2. Find the serial settings

   The ET340 has no display, so take the address, baud rate and parity from the commissioning record or the configuration tool. Out of the box the protocol gives address 1, 9600 bit/s, no parity and 1 stop bit. Enter the same values in the Edge serial client.

3. Wire the RS-485 pair

   Connect A- to terminal 9, B+ to 8 and the common to GND on 10, or use one RJ45 socket. The screw terminals, both RJ45 sockets and the optical port are one port in parallel, so connect only one master. Link A- (9) to T (7) on the last device on the bus.

4. Make two reads

   Read the identification code at 0x000B, one register, and expect 345. Then read L1-N voltage at 0x0000 for two registers, decode it low word first as in the worked read below, and compare it with a voltage measured at the terminals.

5. Check wiring and counting mode

   Read the wrong-connection status at 0x1105: every bit at 0 means the voltage sequence and current directions are right. Read the measurement mode at 0x1103 (0 is A, 1 is B) before relying on exported energy, then add current, power and energy points from the same table.

Common questions

Why does voltage read as millions of volts?

The client is taking the high word first. The EM300/ET300 protocol sends INT32, UINT32 and UINT64 values least significant word first, with each word high byte first. Swap the two registers, then apply the scale: 2300 at 0x0000 is 230.0 V.¹

How do I check readings when the ET340 has no display?

Start with the identification code at 0x000B, which reads 345 on the ET340, then compare voltage with a measurement at the terminals and power with a known load. The wrong-connection status at 0x1105 flags reversed phases and a wrong voltage sequence, and reads 0 when the wiring is right.^1, 2

Does the ET340 support Modbus TCP?

Not on the transducer itself. The order code lists one output, S1, the RS-485 Modbus RTU port, and the datasheet describes no Ethernet port. Read it over RS-485 through a ZMB-31 Modbus Interface or the Gateway serial port.²

Why does exported energy stay at zero?

Check the measurement mode at 0x1103. In mode A (easy connection) the ET340 counts total energy without regard to direction, current and power are always positive and kWh(-) does not increase. Mode B keeps imported and exported energy apart. Have the installer change the mode with the configuration tool if export must be counted.^1, 3

Can I use the RJ45 sockets and the screw terminals at the same time?

No. Carlo Gavazzi states that the screw terminals, both RJ45 sockets and the optical port are the same Modbus port in parallel, and only one can be used at a time. The two RJ45 sockets let you daisy-chain the bus with patch leads: pin 4 is B+, pin 5 is A- and pin 8 is GND.^2, 3

Is the ET340 a billing meter?

The datasheet gives class 1 active energy to EN 62053-21 and lists CE as the only approval, with no MID certification. Treat it as a monitoring and cost-allocation transducer and use an approved meter where billing is required.²