Automatization of Helmholtz Coil System Based on NI PXI Platform

[Serob_ANEL]

Contact Information

Country: Armenia

Year Submitted: 2017

University: Armenian National Engineering Laboratories (ANEL), National Polytechnic University of Armenia, Yerevan, ARMENIA

List of Team Members (with year of graduation): Amalya Hakobyan (2019), Lusine Hovhannisyan (2018)

Faculty Advisers: Serob Muradyan, Research coordinator, ANEL

Main Contact Email Address: serob.muradyan@anel.am

Project Information

Title: Automatization of Helmholtz Coil System Based on NI PXI Platform

Description:  

An automated system is designed based on NI PXI platform and LabVIEW programming environment to create controllable magnetic fields. The program reads the data from a file with a desired magnetic field pattern, compares these values with the magnetic field in the system and sets a certain current level in the Helmholtz coil system to generate the magnetic field. The system is used to simulate the Earth's magnetic field during geomagnetic storms and to study the influence of these storms on biological objects.

Products:    

NI PXIe-1082 Chassis,

NI PXIe-8135 Embedded Controller,

NI PXI-4130 Power SMU,

NI PXI-4071 FlexDMM,

LabVIEW Development System,

NI DIAdem

DC Milligauss Meter model MGM (by AlphaLab, Inc.)

The Challenge:

Controllable weak magnetic fields are widely used in biology and medicine to study the influence of these fields on biological objects. To study the influence of magnetic fields with different characters and different patterns on the objects under the study, one should have a very flexible and fully automated system. To simulate geomagnetic storms and to study the influence of those storms on biological objects we have designed and created an automatized Helmholtz coil system based on NI PXI platform and LabVIEW programming environment. Our system can create along its axis slowly varying magnetic fields in the range of ±50000 nT (±0.5 Gs) with any given pattern and with few nT precision.

The Solution:

To have a weak (about 0.5Gs), uniform magnetic field in the volume of 20cm×20cm×20cm for further biomedical studies, we have built a one-axis Helmholtz coils system. Our coils have a R = 60cm radius and are made of a copper wire with 1.2mm in diameter. In each coil we have n = 30 turns.

With our Helmholtz coils, we have used a DC Milligauss Meter model MGM (by AlphaLab, Inc.) and a NI PXIe system (by National Instruments) to have fully controllable magnetic fields. Our NI PXIe system consists of a NI PXIe-1082 express chassis, a NI PXIe-8135 controller, a NI PXI-4071 digital multimeter and a NI PXI-4130 power source measure unit (Power SMU).

The NI PXI-4130 is a programmable SMU, which feeds current to our coils and is capable of providing up to 2A current with 100µA resolution (10nA resolution in 200µA range).

We use the NI PXI-4071 digital multimeter along with the MGM monoaxial magnetometer to measure the strength of the magnetic field. The MGM milligauss meter measures the magnetic flux density in the direction of the sensor in a range from -1999.99 to +1999.99mGs, with a resolution of 0.01 mGs over the entire range. This gaussmeter is equipped with an output jack for an analog voltage output. We have connected that voltage output to the NI PXI-4071 -digit digital multimeter, which has 100nV resolution in a range from -1 to +1V. The usage of NI PXI-4071 enhanced the measurement speed and the resolution of our magnetic flux density mea­surements and allowed to transfer the measurements to the NI PXIe-8135 controller.

A computer program has been developed in the NI LabVIEW environment to automatize the system and simulate the Earth’s magnetic field during geomagnetic storms along the axes of the system.

The program reads the given pattern of a magnetic field and generates a similar field in the system along the axes of the system. The program reads the value of the current magnetic field in the system and compares it with the desired value of the magnetic field. From this comparison, the program calculates needed changes of the current through the Helmholtz coils and controls the output current of the SMU to create the desired field.

The front panel of the developed program is shown in the “Figure 1”.

Figure 1. The front panel of the created program.

On the front panel the desired magnetic field, created magnetic field by the system and the magnetic field in the system are graphically displayed.

The program starts with the opening of a dialog box that prompts the user to select a TDMS file from which the values of the magnetic field pattern would be imported.

The amplitudes of generated by the system magnetic field and desired data are represented with graph indicators on the front panel of the program. “Stop” and “Save” buttons are needed to stop the program and save the measurements into the computer file in TDMS file format.

With the developed program, we can create various magnetic fields in the system along its axes. In particular, we have simulated in our system the changes of Earth’s magnetic field during magnetic storms: “Figure 2” and “Figure 3”.

Figure 2. Simulation of Earth’s magnetic field during a magnetic storm (Ex1).

The upper curve (blue) is the desired field; the bottom one (red) is the magnetic field generated by the system.

Figure 3a. Simulation of Earth’s magnetic field during a magnetic storm (Ex2). The upper curve (blue) is the magnetic field generated by the system; the bottom one (red) is the desired field.

Figure 3b. Simulation of Earth’s magnetic field during a magnetic storm (Ex2).

The desired (red) and created by the system (blue) magnetic fields on the same graph.

As one can see from “Figure 2” and “Figure 3”, the generated by the system magnetic field repeats the desired pattern with a noise level of a few nT.

We have also generated “zero” magnetic field, in our system. In this case, the system tries to compensate the Earth’s magnetic field by generating an opposite field (“Figure 4”).

Figure 4. Simulation of “zero” magnetic field in the system.

The measurements show that with the developed system it is possible to create magnetic fields with the given values with a better than +/- 4 nT precision.

The use of LabVIEW and NI hardware were essential for our project due to their high flexibility and modularity. The used by us NI hardware is fully configurable with LabVIEW and can produce magnetic fields with different patterns. Due to the modular character of NI products, we can easily extend our system to have magnetic field along three axis, which is essential for our biomedical experiments.

<Level of completion> Fully functional

<Time to build> 6 months

<Video>

https://drive.google.com/file/d/0B34W2Ze0bmG7LVNFUDc2TlVTaEU/view?usp=sharing

https://drive.google.com/file/d/0B34W2Ze0bmG7NW1obU11N05nZ3M/view