---

Fig 1.  Foc2 Focus Profile (wide)

 

Fig 2.  Foc2 Focus Profile which was rejected due to "Quadratic values indicate poor/invalid profile"

A Geomagnetic Monitoring Station is being added to the Observatory in Spring 2025 for monitoring changes in the earth's magnetic field and to supplement and build upon the Observatory's existing Aurora monitoring using AllSky Camera and new NorthCam Camera.
Earlier notes regarding selection of SAM III System are covered in: Review - Potential Geomagnetic Monitoring Station (2025-01-24)

SAM III Order arrived today (2025-03-18) and installation plan is being developed.

  

 

Questions:

Q.  How are cable wires fitted to the SAM III Controller Box.
A.  Bared ends of wires are inserted into appropriate slots in the green 10-position pluggable terminal block X2. , and screws tightened. 
    After double checking that correct wires are in their correct slots, insert green adapter bars in port on SAM III controller box
          1 GND X
          2 Signal X
          3 +5Vdc X

          4 GBD Y
          5 Signal Y
          6 +5Vdc Y

          7 GBD Y
          8 Signal Y
          9 +5Vdc Y

         10 Not used.

Q. Identifying Cables to/from Sensor Sensors ?
Three CAT6 cables should be clearly identified at both ends,  marked X, Y, Z according to which axis they will each be connected to.

Q.  A standard 'scheme' should be defined to detail the particular wires in the CAT6 cable that will be used for connecting to the GND, OUT and VCC pins on the FG-3+ sensors and to the relevant slots on the Controller Box.
       GND  -  Blue Wire  = Ground
       OUT   -  Orange Wire     = Sensor output
       VCC  -  Brown Wire  = +5 V Power

Q.  How to ensure that water can't enter to the Piped Sensor Unit at the point of cable entry. (3 Cat6 cables and 1 temperature cable)
A.  Inverted U Tube ?, Expoxy Filler, 

Q.  How to build  'cage' for mounting the three FG-3+ sensors.
A.  Circular Wood Cage ? ,   3D Printed Cages from Torc ?, 

Q.  How to wire up the FG-3+ sensors (including 10 µF, 25 V tantalum capacitor & 100 nF 25 V multi-layer ceramic capacitor ) ?
A.  Refer to wiring plan in manual

Q.  How to connect wires to 3 pin adapter using metal tags. How are the metal tag inserted into plastic adapter ?
A.  From Installation Guide:

 A 3-pin single inline header connector and contacts are supplied for connecting cable to each sensor. Crimp or solder the sensor cable wires to the contacts and insert them in the SIL header connector. The SIL header connector has slots on one side, and the tiny tabs on the contacts must be inserted on this side. Do not solder wires directly to the sensor. The sensor pinout is indicated on the sensor label and in the drawings below.

The socket contacts require a double-crimp, one for the conductor and one for the insulation. If you do not have a crimping tool and must solder the wires, it is suggested you cut the insulation crimp fingers off of the contact (otherwise, it is unlikely you can fold the fingers enough to make them fit the header connector). You will need to fold the conductor crimp with a pair of miniature pliers. Do this very carefully to avoid damaging the contact. Apply a very small amount of solder – if you apply too much solder it will wick up into the socket.

Before inserting the single inline (SIL) header onto the sensor pins, put a small amount of dielectric grease (for example, Permatex 81150 available at most automotive parts stores) on the sensor pins. The amount of grease used should be small enough that it is not visible on the pins. This will help prevent corrosion if the sensor is used in outdoor applications. The header has no built-in polarity indicator so it should be marked with nail polish, paint or tape to indicate proper orientation.

Q.  Does the existing 12mm Male Plug from the A/C Power Adapter Unit need to be replaced with either the longer 14mm plug or with 12mm plug with locking nut. ?
A.  Controller Unit was tested with existing 12mm Male Plug and it initialises ok.  A disconnection/reconnection occurs if the plug is physically rotated, but not under general use. It seems secure enough.
( I'd rather not change the plug as this requires cutting off the existing male plug and soldering/crimping wires to the new plug and then rely on screwed connection on working loose.)

Q. How should the X, Y & Z Geomagnetometer Sensors be orientated ?   
A. As per construction manual
   X    North-South ,   pins  SOUTH
    Y    East-West,       pins  WEST
    Z    Vertical,            pins  UP

Q. What entries should be made in the SAM_VIEW setup/settings ?
A. Settings
  Owner or Station Name  :  Clair Observatory
  Location :                             Ellon, Scotland 
  Longitude, Latitude            02.00W,   57.32N  
  IARU-Locator :                    IO87xh    

Q. What are expected 3-axis field strengths ?
A. Using the calculator at World Magnetic Model 2025 Calculator (geomag.bgs.ac.uk) the expected field strengths at the Observatory for 2025-04-01.

  X:   16467nT   (4.4 nT/year)
  Y:      -100 nT   (59.1 nT/year)
  Z:   47326 nT   (32.8 nT/year)

  H :   16468 nT  (4.0 nT/year)         (Horizontal Intensity,  from X & Y vertor sum)
  F :  50110  nT    (32.3 nT/year)     (Total Intensity)

  D :  -0.348 deg East       (12.4 arc min/year)
   I  :    70.814 deg Incl'n   (0.5 arc min/year)   ' Angle from Horizontal

- See also  What are the geomagnetic components ?  (intermagnet.org)         

Update 2025-03-19  (SAM III - PC Connection)

- Created program folder  'C:\More Programs\SAM'   and copy into the folder the files from
     '..\Software-Firmware\SAM3 Applications'
     '..\Software-Firmware\Runtime Libraries'

- Installed SABRENT USB-Serial Driver
.   CD .. /Windows/PL23XX_Prolific_DriverInstaller_v301-WIN11/PL23XX-M_LogoDriver_Setup_v301_20211221.exe

    - Used PL23XX_checkChipVersion_v1020.exe' to check 'COM4' this gave the meessage :
   "This is a PL-2303 GS chip"

- Made a trial connection to SAM III unit
  - Connect USB-Serial Cable to Computer
  - Appears as "Prolific PL2303GS USB Serial Com Port (COM4)             (COM4 on Development/Analysis Computer)
- Connect USB-Serial Cable between Computer and SAM III box via Serial Pass Through Cable)

- Opened SAM_INI_v2-0.exe
- Selected COM Port (COM 4)
- Set default values used to confirm values on Form are defaults.
  (proven by changing a value and then using Set Default Values to see it overwrite the manually changed value)

- Tried 'Send parameters'.
     After running to 100%, 'Error!' dialog shown with message "Error while writing parameter set!"
Tried 'Receive parameters'
    After running to 100%, 'Error!' dialog shown with message "Error while reading parameter set!"

A Port Monitor confirms that data is coming from the SAM Unit with data every second, like
  20.03.25 15:57:01: X,,Y,,Z,

-If SAM_INI_v2.0 is opened and connected to COM4 with the SAM III in command mode (F1) and
'Send Parameters' is used, SAM_INI runs to c. 50% and then displays message "SAM does not respond".

 -  Trying again :
     'Receive Parameters' ,  trackbar runs to 100% and message 'Parameter read successful.." appears

 Trying again
     'Send Parameters' :  trackbar runs to 100% and message 'Parameter write successful.." appears
     After a successful 'Write', the SAM box automatically resets itself.

 To do:  
- Dig a 120 cm deep hole to contain 3-axis geomagnetometer sensor fixture (see Update 2025-03-23 to Updates 2025-03-25 below)
- Prepare 3 CAT6 cables,  one cable for each sensor
- Prepare Temperature Monitor  (see DS18B20 Waterproof Digital Temperature Sensor (2025-03-19)

Update 2025-03-23 (Hole)

Hole that will contain the 3-axis geomagnetometer sensor fixture has been commenced on 2025-03-21 and reached 45 cm depth.  Pictures below show status of hole on 2025-03-23 after reaching 68cm.

Hole that will eventually contain 3-axis geomagnetometer sensor fixture Hole has reached 68cm deep at the time of the photo another 52cm to go in red subsoil / drift deposit		Hole location relative to Observatory where the SAM III Monitor will reside Offset Distance 10m Cables will eventually be run below the lawn.

Update 2025-03-24 (Hole)

Hole that will contain the 3-axis geomagnetometer sensor fixture has now reached 100cm depth.  Another 20cm to go

Update 2025-03-25 (Hole)

Hole that will contain the 3-axis geomagnetometer sensor fixture has been completed after reaching 120cm depth. 

Completed Hole for the 3-axis geomagnetometer sensor fixture Hole depth is 120cm		Detailed image showing lower part of hole
Side view of hole 120cm depth		Side view of hole 120cm depth.

Update 2025-03-26 (Sensor Fixture Progress)

Pipe work for the building the fixture that will house the 3-axis geomagnetometer sensors (X, Y & Z) & the temperature sensor was purchased today (2025-03-26) form local hardware shop.   Items comprised FloPlast 40/43 mm diameter straight pipe, angled junctions, and end stops. Junctions will eventually be joined/sealed using special FloPlast solvent cement.

A mock-up of the fixture showing the rough positions of sensors is shown in the picture below.  Note that the straight pipe has not been cut to size yet, and the top horizontal sensors will be placed at 90 deg to each other in the final build (not the 180 deg positioning used in the rough mock-up).  Cables to the magnetometer sensors is'nt shown here.




Update 2025-03-27 (Sensor Fixture Progress)

Pipe work for the building the buried sensor fixture has been cut to length and the entire assembly loosely fitted together (see pictures below) :


  

3 x 15m lengths of CAT6 Cable have been cut from 100m reel previously purchased.  Required cable length is around 12.5m, so these 15m lengths have an excess which will be trimmed off during final tieback to the Observatory.

Update 2025-03-27 (Sensor Fixture Progress)

End caps and axis endings were joined together with solvent glue.  (x4)
Wooden  Circles glued in place internally (these will hold the magnetometre sensors in place)  (x3)

Small circuit board built for each magnetometer,  and connected to a Cat6 cable and to the magnetometer. (x3)

Each circut / magnetometer was connected to the SAM III controller in turn and tested to ensure it was worked (x3)
(one circuit initially didn't work due to a bad solder connection and had to be fixed).

Made a matrix of tests after noticing that one of the magnetometers showed readings that were offet from the others when all 3 sensors were pointing the same direction, as if it had a different bias.

Each magnetometer was connected in turn to Circuit 1 (x), Circuit 2 (y) & Circuit 3 (z) and the reading recorded when the magnetometer was pointing North (X),  East (Y), and Down (Z). This produces a 9 x 3 matrix of values (see below)

Sensor	Circuit		Sensor Orientation
			North (X)	East (Y)	Down (Z)
Magnetometer 1	Circuit A (x)
	Circuit B (y)
	Circuit C (z)
Magnetometer 2	Circuit A (x)
	Circuit B (y)
	Circuit C (z)
Magnetometer 3	Circuit A (x)
	Circuit B (y)
	Circuit C (z)
Expected Values			16467	-100	47326
(BGS 2025 Model)