Design of a Fluxgate Weak Current Sensor with Anti-Low Frequency Interference Ability
Zhiguang Wang
Round 1
Reviewer 1 Report
This paper investigates a shielded current sensor based on fluxgate with reasonable working range and bandwidth. However there are several problems that should be addressed before I can considering recommend it for publication:
1. Magnetic sensors based on fluxgate, or any other types of sensor, possess large 1/f moise. It means that the LOD of the sensor is strongly dependent on the measurement frequency. Authors claim a measurement range of 1mA-1A with bandwidth of DC-16kHz. It is necessary to measure 1mA at DC conditions, maybe using, square signals with very low frequency, so that we can see the step change of the electrical output.
2. Fig.4 shows the comsol simulation of the magnetic core. It looks like that magnetic flux is only distributed inside of the core, which is not the purpose of the setup. The existance of the magnetic core is concentrate the magnetic flux to the area of the fluxgate.
3. Shielding is important for current sensor, but the introduction of a high permeability magnetic shell will certainly affect the concentration effect of the magnetic core. Authors need to clearly demonstrate the positive and negative effect of the magnetic shielding.
4. Authors need a lot of effort to rewrite the manuscript. There are a lot of logic problems. In page 2 "...which is not mentioned in any of the aforementioned literature." By saying it, I surpose authors are doing some novel research that other researchers have not done. Buth then authors listed refs 14-17 which are related to the exeternal magnetic interference. It means it is not a totally new topic.
5. All the fiures and table need to reorganized.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors have developed a shielded, fluxgate type current sensor suitable for weak current measurement. Methodology and experimental results are well described in the manuscript. I suggest following comments to be reflected in the manuscript for further improvement.
-Introduction, 6th line of 2nd paragraph: 0.1 nT is in magnetic field form while the sentence discusses about current sensors. The sentence should be modified to explain how precise 0.1 nT is for current sensors.
-Introduction, the last line of 2nd paragraph: The cited reference 17 is a conference paper and thus seems to be lacking some information such as shielding material. The authors should cite published version of the research “A Fluxgate Current Sensor With a U-Shaped Magnetic Gathering Shell” IEEE TRANSACTIONS ON MAGNETICS, VOL. 51, NO. 11, NOVEMBER 2015. And then, the authors should discuss little bit more in detail about the technical issues found in the above-mentioned research.
-Subsection 3.1: Offset and offset drift of the fluxgate sensor chip should be important when detecting DC and low frequency current. It is encouraged to estimate their effect based on the sensor specification. If the effect is estimated to be critical for 1mA resolution DC current detection, additional measurement and discussion in Section 4 is suggested.
Following are just the editorial comments.
-Subsection 3.1: Unit for magnetic intensity should be mT, not Mt.
-Subsection 3.4, 4th line of 2nd paragraph: Pomo alloy might correctly be Permalloy?
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
According to the experimental result added as Fig. 13, I understand the developed sensor has at least short time DC stability for 1 mA detection. For long time stability, fluxgate chip’s offset drift (for example typically 5 nT/K against temperature) should be much smaller than the magnetic field by created by 1mA source current. To be clear for readers, please specify the current setting in the simulation shown in Fig.4 so that the readers can understand the field strength at the fluxgate chip against the source current; I couldn’t find the information on simulation current setting in the present manuscript).
Subsection 3.1 still contains wrong unit “mv/mt”. Also recheck the English grammar especially for the newly added paragraphs (for example, regarding the Ref.17 in the intro, "detains in detail" sounds wrong.)
Author Response
Thank you for your time and efforts. We have revised the manuscript according to your comments.
