LISSA FM Magnetorquer Test

Introduction

Test Description: Test the generated magnetic field of the flight model magnetorquers for LISSA. This test is based on the procedure developed by the York University for the Iris mission. Please follow the test results spreadsheet provided and fill it in as the test proceeds.

Completed: 

Documented by: Riley Sweeney

Resources Required:

• Tools: 1 mm Allen key

• Hardware and Equipment: 3x UMS-0053 FM magnetorquers, programmable power supply (for magnetorquer), MMC5983/Arduino magnetic sensor , 3x Hanmatek HM310T power supplies (for Helmholtz cage)

• PPE: FM testing will likely occur in the clean room. Please follow all clean room safety guidelines. Please wear an ESD bracelet and use ESD mat when working with electronics.

Verification Activities: R-LIB-ADC-006-6969. R-LIB-ADC-042-6976

Pass Criteria: The magnetorquers shall limit their current draw (R-LIB-ADC-006-6969). The magnetorquers shall produce a dipole moment of at least 0.2 Am^2 (R-LIB-ADC-042-6976).

Test Set-Up

Setting up the measurement table:

1. Ensure all electronics, magnets, or any source of magnetic interference is moved away from the test space.

2. Mark an orthogonal cross on the test table to define an origin and x- and y-axes. 

3. Measure and mark points for placing the magnetometer. Follow the outline spreadsheet for insight to how and where to mark the points. Number each of these points for repeatability.

4. The first sheet of test results spreadsheet includes constant values which are used to perform calculations. Check all of these and update if needed.

Setting up the Helmholtz cage:

1. Place the cage structure on top of the measurement table.

2. Place three HM310T power supplies next to the Helmholtz cage to power it.

3. The cage is made of 3 pairs of square rings, for the x-,y-, and z-axes. Each pair of rings has a lead of wire extending from it, gather the three pairs for each cardinal axis.

4. Starting with the x-axis (the two horizontal rings), connect one lead to power and one to ground on a power supply. Mark the axis the power supply connects to. Repeat for the y- and z-axes.

5. Set the current limit on the power supplies to 5 Amps. Any current higher than this may damage the coil's wires.

Zeroing the Helmholtz cage:

1. Place the magnetometer on the origin point and connect to a laptop via USB.

2. Open and upload MMC_Avg_Measurement.ino to begin reading measurements on the serial monitor.

3. Starting with the z-axis power supply, turn on the output and gradually increase the voltage, while monitoring the magnetometer readings. Use coarse adjustments to get the z-axis under 10 mGauss.

4. Leave the z-axis power supply running, and turn on the y-axis power supply, and repeat the previous step, then finish with the x-axis.

5. The axes of the cage are not perfectly orthogonal, and neither will the orientation of the magnetometer, so adjusting one axis will likely affect other axes. Once all three axis are near zero, fine adjustments can be made.

6. Ultimately, it will be too tedious to perfectly zero the cage, the goal should be getting all three axis to read less than +/- 5 mGauss.

Test Procedures

The test process will follow the Excel template provided.

1. Attach the magnetorquer to the stand and place it on the origin. Connect the alligator clips on the remaining power supply to the wires on the magnetorquer. Keep note of which clip is connected to each wire, they will need to be switched.

2. Set the magnetorquer's power supply to the first voltage indicated in the test template and begin taking magnetometer readings at each location. Make sure to wait a few seconds for the magnetorquer to fully charge before taking the first measurement. Mark the results for all three axes in the test results for each measurement position.

3. Once all measurements have been taken, follow the results spreadsheet to increase the input voltage to a new value and repeat the measurement process. 

4. Once all measurements for all power levels have been taken, readings for the XY-plane have been completed. Rotate the magnetorquer into the Z-plane and repeat the previous steps.

5. Repeat this process for all individual magnetorquers.

Test Close-Out

Include information about apparatus tear down, clean up, consumables storage, and how to store test data.

Data Analysis

Provide step-by-step instructions for data analysis, including location of data storage.

1. The test results spreadsheet will do all calculations automatically after filling in the magnetometer readings. Check the Calc sheet and the Result Summary sheet. This will provide the results for both pass/fail criteria.