Technical Article

Accomplishing Closed-Loop Accuracy in Advanced Open-Loop Current Sensors

November 30, 2020 by Lily Kim

This article highlights J&D the development of open loop current sensors to measure higher current with low power consumption.

The demands of engineers, designing in power electronics systems of distributed resources, are the current sensors with low power consumption. And the current transducers that have higher current measurement with high accuracy, are desired.

To meet these demands, J&D developed open loop current sensors to measure higher current with low power consumption. See figure 1 to find the graph of accuracy vs. temperature / current range characteristics. The open loop technology of IDCS series uses a potentiometer to compensate DC offset and secondary output. At this time, J&D designed a schematic diagram that protects temperature characteristics that are exacerbated by potentiometers.

As you can see in the graphs from Figure 1, comparing 1-1 and 1-2, J&D has improved temperature characteristics by the advanced schematic diagram.

If you see the figure 1, high error ratio appears in the high current and high temperature. To solve this issue, zero-near DC offset, zero-drift IC and high permeability permalloy core have been used(The advanced schematic diagram, figure1-2). With this schematic diagram, the error ratio has been improved by 0.5% accuracy in the higher temperature.

As power electronics systems of distributed resources get smaller, J&D was concerned what if humidity and temperature issues occur. This is because it is highly related to the space inside that "high humidity" inside affecting the electrical devices to the efficiency of components, and when "the temperature of the primary conductor gets higher” than 100°C, it will affect the reliability of the product and will reduce its lifetime. J&D has built-in humidity and temperature sensors as options to protect the equipment from humidity and high temperature so that users can find the dangers.


Figure 1: Comparison of the previous open loop CTs and J&D New IDCS series open loop CTs by the graphs of accuracy vs. temperature / rated current
Figure 1: Comparison of the previous open loop CTs and J&D New IDCS series open loop CTs by the graphs of accuracy vs. temperature / rated current



These IDCS Series are innovative open-loop current sensors whose performance is said to approach that of closed-loop transducers, improving control and system efficiency at a much lower price.


1) Features

(1) IDCS Series have a wide range of unipolar power supply, 5~24V and bipolar power supply, ±15V.

(2) Since the CTs are made with lighter weight, this saves up to 15% of weight of the equipment.


2) Advantages

(1) J&D’s IDCS series got a patent to 6 hall elements enabling to improve position error. Hall elements’ positions are designed to be less affected when mounting on busbars.

(2) Schematic design for faster response times. IDCS Series has a response times with 3 μs, faster than the general open loop CTs’ response, 10~5 μs.

(3) A wide range of frequency. (-3dB) is shown in IDCS Series at up to 50kHz, while other open loop CTs has it at 25kHz.

(4) IDCS series solid core CT supports busbar mounting, maintaining accuracy even at high temperatures.

(5) Proper to protection of DC/AC current.

(6) High current measurement is able to be done with less power consumption.


3) Optimized design

(1) Types of Busbar / Pannel mounting

(2) Designed to be safe from vibration and shock vibration

(3) Suitable size for using in a compact power Inverter.


4) Options

(1) Humidity sensor - Built-in humidity sensor protects the equipment from high humidity that affects performance of power electronics systems.

(2) Temperature sensor - Built-in temperature sensor protects the equipment from high temperature that can be dangerous and cause damage to the power electronics systems.

(3) 3 Connector types


There are 3 types of connector for IDCS Series, Type A, B and RJ12. See figure 2 for details.

  • Type A : Molex 39-28-8040 (Old# 5566-04A-210)
  • Type B : Molex 5045-04AG or Geoyoung LPH01-04
  • The Plug & Play RJ12 Port : A RJ12 connection makes quick, easy, and reliable wiring, and it also prevents wiring errors.


The Benefits for Inverter / ESS / UPS 

As you can see in the Figure 3, J&D Split core CT, IDCS Series, got a patent on 6 hall elements. And it is designed to be easily mounted on the busbar, and to be appropriate for power metering of AC/DC power meter. The IDCS series' safety from vibration and shock and its suitable size for using in a compact power monitoring are also one of the advantages for power electronics systems of distributed resources. Thanks to its CTs’ advantages, IDCS Series used with Powerside’s P-Qube 3 meter has been registered as a reference for applying to ESS(Energy Storage Systems) developed in LS Electric, from Korea.


Figure 2: IDCS series
Figure 2: IDCS series

“Worry costs. The cost can be money, time or chance. With J&D, you no longer have to worry about whether to use an open-loop or a closed-loop. We provide solutions that can be free from the worries. The IDCS Series’ compact size, low power consumption and the competitive price give you a chance to accomplish something great.”


This article originally appeared in Bodo's Power Systems Magazine.