Wednesday, November 25, 2020 · 16 min read
Direct Current Current Transducer DC-CT® Technology Explained
The recently introduced next-generation SIRIUS XHS power analyzer is a giant leap in data acquisition and ADC technology. It is powered by the new HybridADC technology (analog-to-digital converter) developed specifically for the new SIRIUS XHS data acquisition systems.
HybridADC technology
HybridADC offers a 15 MS/s sampling rate with a high 5 MHz bandwidth acquisition and also high dynamic alias-free acquisition with up to 1 MS/s sampling rate. Everything is integrated into one single device. This is a break trough in the data acquisition world. One device replaces what would traditionally need two totally separated data acquisition devices.
The new HybridADC technology from Dewesoft
SIRIUS XHS-PWR data acquisition device for EV testing with integrated high precision wide bandwidth DC current transducer based on the Platiše flux sensor
SIRIUS XHS line also includes a device intended for E-mobility electric vehicle testing called SIRIUS XHS-PWR. The DAQ device is designed for in-vehicle direct measurement of current, voltage, and power.
It integrates innovative DC-CT® current sensing technology (DC Current Transducer) from ISOTEL for accurate current measurements in the most demanding applications such as very high current peaks as well as leakage current measurement.
The current transducer uses patented DC-CT® technology based on the Platiše Flux Sensor. DC-CT is a registered trademark of ISOTEL. It represents the latest current sensing technology with ranges 100A, 500A, and 1000A, a wide 1 MHz bandwidth, and ultimate performance. Excellent linearity, precision, accuracy, immunity to external magnetic fields, low offsets, and extremely low-temperature drift are achieved at low-power operation.
The device can also directly measure the voltage up to 2000V peak (CAT II 1000V) with up to 5 MHz bandwidth.
Check the complete SIRIUS XHS-PWR technical specifications.
The device is extremely compact and perfect for direct installation into a vehicle with the power lines leading through the device. It has an IP65 degree of environmental protection which allows usage in harsh environments and during rough drives.
Let's look more closely at how the new DC-CT technology works.
What is DC-CT® technology and how does It work?
DC-CT represents an innovative principle of isolated measurement of DC and AC currents. Within a magnetic core, magnetic flux can only be measured if it is non-constant, changing, or alternating. Since a DC current generates a constant magnetic flux the innovative principle redistributes this flux among two or more paths periodically in a single core. If we observe this magnetic flux from one path only it appears alternating and is therefore easily measured by a simple winding, which voltage is proportional to the measuring current.
DC-CT current technology - the original technical white paper:
This was achieved by inventing a current-controlled variable reluctance - a vital component, composed of a kind of infinity winding, embedded into a gap-less core retaining all of the good properties of high permeability materials. This new type of flux sensor is named after the inventor: Platiše Flux Sensor and the invention is branded under the DC-CT® registered trademark by ISOTEL.
Comparing this principle to widely used Hall-based sensors inserted into a magnetic core, the DC-CT solution does not create any air-gap, retaining very high sensitivity and immunity to external magnetic fields. In addition, the new DC-CT sensing principle is temperature independent.
Comparing this principle to the most widely used high-end flux-gate transducers, a flux-gate method adds energy to the core to alternate the flux between the maximum and minimum operational limits of the core consuming a significant amount of energy. Value of the measuring current can be extracted from the 2nd harmonics, pulse-width-modulation in self-oscillating solutions, or other methods.
High-end flux-gate solutions require three cores instead of just one as in the case of the DC-CT current transducer. Two of them are required for sensing, operating in opposite directions to reduce injected noise, and the third is used to extend the AC bandwidth. Flux-gate resets a core repeatedly, while the DC-CT is on request only to demagnetize the core.
Comparison table of DC-CT versus other current sensor types:
| Type | Isolated | Range | Bandwidth | Linearity | Accuracy | Temp. drift | Consumption | |
|---|---|---|---|---|---|---|---|---|
| DC-CT | DC/AC | Yes | High | High | Excellent | Very High | Very Low | Medium |
| Fluxgate | DC/AC | Yes | High | High | Excellent | Excellent | Low | High |
| Hall | DC/AC | Yes | High | Medium | Medium | Medium | High | Low-Med |
| Shunt | DC/AC | No | Medium | Medium | Good | High | Medium | High |
| Rogowsky | AC | Yes | High | High | Good | Medium | Low | Low |
| CT | AC | Yes | High | Medium | Medium | Medium | Low | Low |
DC-CT is, therefore, energy-efficient, of compact size, low noise, and cost-effective. Existing products range from 2 A and up to 2000 A, up to 1 MHz bandwidth, with target accuracy from 0.1% down to 0.01%. Other potential uses include DC/AC residual current sensors of class B+.
