Precisely Calculating Electrical Power using a QuantumX and catman Software

June 8, 2025 admin

How to carry out the necessary steps using a QuantumX MX403B measurement module and catman DAQ software.

Calculating electrical power

In many applications acquiring electrical signals and then subsequently calculating power and analyzing signals in the time domain and frequency range is a topic of growing importance. This article provides practical tips on how to carry out the necessary steps to complete these tasks using an HBM QuantumX MX403B and HBM catman software.

Electrical actuators are used in an increasing number of applications such as in elevators, escalators or as car components. Actuators (e.g. drives or valves) are rapidly replacing hydraulic systems used for calculating electrical power up to now. Hence, acquiring “electrical quantities,” such as voltage and current is becoming increasingly important.

The QuantumX data acquisition system allows for acquisition of both electrical quantities and typical physical quantities, and the QuantumX MX403B 4-channel measurement module has been developed specifically for precise acquisition of voltages. QuantumX MX403B module also enables small differential voltages at a high electrical potential to be measured.

Note: Measurement of hazardous voltages may only be carried out by trained personnel. Measurement categories as defined in IEC 61010 play an important role in helping you choose the right measuring equipment. Please also refer to the safety instructions in the MX403B operating manual.

QuantumX MX403B Data Acquisition System

The QuantumX MX403B module has four isolated differential measurement channels for direct measurement of voltages up to 1,000 V DC or 1,000 Vrms AC. The measuring ranges of 10, 100 and 1,000 V can be freely parameterized. The ranges can enable acquisition of high voltages against reference ground as well as measurement of small differential voltages at a high potential against reference ground. Every channel is equipped with analog anti-aliasing filters, 24-bit AD converters and digital filters, and each can be individually parameterized.

QuantumX modules can be physically distributed and connected within close optical range of the measuring point (optical Ethernet or optical FireWire) to ensure maximum reliability between the measuring point and the PC.

The module permits sample rates up to 100 kS/s per channel and bandwidths up to 40 kHz and can be seamlessly incorporated into the existing QuantumX data acquisition system. The QuantumX solution allows acquisition of all physical measurands from the mechanical, electrical and thermal worlds, completely synchronously. It calculates the signals, establishing itself as a comprehensive complete solution and a valuable tool in research and development.

Measuring Voltage with QuantumX MX403B

Of course, when measuring voltages, it is essential to know at what potential/reference point the measurement is taken. The MX403B module is perfectly suited for measurement, analysis and testing tasks and measures direct voltages on or in energy storage devices or alternating voltages in 1-phase or 3-phase operation in compliance with measurement categories CAT II and III. In 3-phase operation, we distinguish between 3- and 4-wire three-phase current systems, depending on whether or not a neutral is available. This also determines the measurement circuits for determining electrical power.

Three-phase current systems often use the star or Y configuration. The three windings (L1, L2, L3) are connected to a common point in the motor. This “common star point” was led out into the junction box and used for switching from star to delta when starting up a motor in the past.

With the increasing prevalence of electronic converters this is rapidly changing. With three phases, power is added geometrically from the individual power values; since the current is measured in each phase separately, it needs to be multiplied by the voltage of each phase. Only in rare cases can the phase voltage be tapped directly. Therefore, one of the following methods is used:

Calculation of star voltages U1N, U2N, U3N from delta voltages U12, U23, U31.This is inaccurate, however, it is applied in practice
Generation of a reference point outside of the motor via an R or RC network (virtual star). This is more accurate and well suited for balanced loads. However, assuming that the motor is perfectly balanced both in terms of design and behavior, a SINGLE power channel would be sufficient. This needs to be analyzed.

Voltages and currents in the 3-wire system (star connection)

When designing electric motors, special consideration is given to generating balanced loads, i.e. the neutral does not carry current. If the star is not led out (no neutral and thus three-wire circuit), an “external virtual star” can be configured. The G068-2 adapter provided by HBM can be used for this purpose. The G068-2 comprises three RC networks. The box precisely fits onto the MX403B’s banana sockets, however, it limits the range to AC 600 V.

Acquiring Current with QuantumX MX403B

Electric current can be measured based on different principles. While a zero flux converter, shunt or Hall sensor converter allow for precise, phase-synchronous measurements of small currents, current probes are particularly suitable for quick current measurements in 1-phase and 3-phase operation. Current clamps enable a wide range of electrically isolated measurements of alternating currents (often also direct currents) without the current carrying line having to be opened. Furthermore, current clamps are inexpensive and allow for power analysis in applications with less stringent accuracy requirements. Different designs of current probes are available for different purposes (inductive, Hall effect).

The inductive measurement principle results in a phase delay in thecurrent transformer (skewing)between the current clamp’s real current and its output voltage, which needs to be compensated for prior to calculating the power. This involves correspondingly delaying the measured voltage. With some current clamps, the phase angle error varies according to the frequency and over the measuring range, which, of course, impacts on the power calculation! Depending on the measuring range, 3 to 10° can occur at reference conditions. Please note: a perfect sinusoidal voltage, 45…60 Hz, 23° C ambient temperature and 50% relative humidity are used as reference in most cases. Every deviation from this reference can and will impact on the accuracy of the current measurement and thus of the power calculation. Therefore, selecting the right current clamp is of paramount importance. For this reason, HBM directly offers current clamps.

The phase shift needs to be compensated for to enable the power calculation to be performed correctly. The easiest way to compensate for the phase shift and thus determine power is to delay the measured voltage correspondingly. This process is described in more detail below. Now that both electrical quantities have been discussed, we can consider the software required for calculating electrical power.