Electric energy 29.02.2020 11:50 04.03.2020 17:44

In order to provide a detailed analysis of a 3ph network (measuring and monitoring the line and phase voltages, currents, active and reactive power, the power factor, THD voltages and currents and frequencies in the low-voltage network, etc.), you can use the SMM33 module connected to the communication channel of the Foxtrot basic module. For more information about the Foxtrot communication channels, see the TXV 004 03.

The SMM33 module is equipped with inputs for connecting three voltage signals of nominal value of up to 3 x 230 Vef and three fully isolated current inputs up to 5 Aef.

Supply voltage of the device must be connected to the AUX V terminals via a disconnecting device (a switch - see the example of connection.

It must be located right by the device and it must be easily accessible by the operator. The disconnecting element must be marked as such. A circuit breaker with a nominal value of 1A can be used as a disconnecting device, but its function and status must be clearly marked (by symbols "0" and "I" in accordance with the ČSN EN 61010-1).

The measured voltage should be secured e.g. by a 1 A thermal fuse. The measured voltage can be connected via measuring voltage transformers.

The current signals of measuring current transformers with a nominal value of 5A or 1A must be

brought to the terminal couples I1k, I1l, I2k, I2l, I3k, I3l; however, their orientation must be observed (terminals k, l).

The RS-485 communication line should be connected to terminals A, B and the shielding to the GND terminal. The endpoints of the communication line must be fitted with terminating resistors.


Basic technical parameters of the SMM33 module

Supply voltage

85 ÷ 275 VAC / 45 ÷ 450 Hz, 80 ÷ 350 VDC

Power consumption

3 VA/3 W

The over-voltage class and the degree of pollution

III/2 - accoring to ČSN EN 61010-1


galvanically isolated, the polarity is irrelevant

The measured voltage

( Unom = 400/230 VAC) 4 ÷ 500 VAC/2.3 ÷ 285 VAC (phase-to-phase/phase)

Voltage measurement accuracy

± 0.5% from the value ± 0>1% from the range ± 1 digit

Input impedance

660 kΩ ( Li – N )


star pattern

Permanent overload (acc. to IEC 258)

2 x (i.e. 1,000/570 V)

Peak overload

4 x for 1 second ( i.e. 2,000/1,140 V)


45 ÷ 65 Hz

Frequency measurement accuracy

± 0,02 %

Measured current

0.02 ÷ 7 AAC (Inom = 5 AAC);

Current measurement accuracy

± 0.5 % from the value ± 0>1 % from the range ± 1 digit


galvanically isolated

Permanent overload (IEC 258)

14 AAC

peak overload

70 AAC for 1 second

Communication port

RS-485 galvanically isolated, the Modbus-RTU protocol

Active power ( Pnom = 230*INOM W )

the range is limited by the range of measured voltage and current

Measurement accuracy of active power

±2 % ±1 digit

Reactive power ( Qnom = 230* INOM VA )

the range is limited by the range of measured voltage and current

Measurement accuracy of reactive power

±2 % ±1 digit

The power factor P.F. (accuracy)

0.00 ÷ 1.00 ±2 %;

Cos φ (accuracy)

-1.00 ÷ +1.00 L, C ±2 %

THD (accuracy)

up to 25. order, 0 ÷ 200 %, ( ±2 % ±1 digit, pro U, I > 10 % UNOM ,INOM )

Operating temperature

-25 to 60 °C

Maximum wire cross-section for the terminal

2.5 mm2


Fig. 1. An example of connecting the 3ph network analyzer SMM33 to CH2 CP-10x6 (10x8)