Le labo de Michel | LDM #242: Magnetic Anomaly Detector AN/ASQ-504 Part 3: Cesium cell @lelabodemichel5162 | Uploaded 2 years ago | Updated 2 hours ago
This last episode shows the rest of the circuits and the details of the Cesium cell.
00:00 - Intro
01:40 - The photocell
02:44 - Cesium cell, heater and lens
03:56 - Cesium cell temperature regulation
07:40 - Conclusion
Detailed description
The ASQ-504 uses an auto-oscillating circuit which permits to get directly the Larmor frequency.
A 100MHz oscillator (board #1) is used to generate a high frequency magnetic field which permits to activate an electrode-less Cesium discharge lamp.
The lamp illuminates a vapor Cesium cell. The cell is heated to a temperature of 60°C using an AC current at 8 kHz approximately. The temperature is regulated using a temperature sensor closed to the cell. The regulation circuits are located on board #2.
A photocell is used to detect the light coming from the lamp and passing through the Cesium cell. The signal is amplified and fed to a coil surrounding the cell. When the coil generates a signal at the Larmor frequency there is a change of the transparency of the Cesium cell which is detected by the photocell. Thanks to the feedback the circuit oscillates naturally at the Larmor frequency which is proportional to the magnetic field. A filtered signal at the Larmor frequency is the output of this MAD.
This last episode shows the rest of the circuits and the details of the Cesium cell.
00:00 - Intro
01:40 - The photocell
02:44 - Cesium cell, heater and lens
03:56 - Cesium cell temperature regulation
07:40 - Conclusion
Detailed description
The ASQ-504 uses an auto-oscillating circuit which permits to get directly the Larmor frequency.
A 100MHz oscillator (board #1) is used to generate a high frequency magnetic field which permits to activate an electrode-less Cesium discharge lamp.
The lamp illuminates a vapor Cesium cell. The cell is heated to a temperature of 60°C using an AC current at 8 kHz approximately. The temperature is regulated using a temperature sensor closed to the cell. The regulation circuits are located on board #2.
A photocell is used to detect the light coming from the lamp and passing through the Cesium cell. The signal is amplified and fed to a coil surrounding the cell. When the coil generates a signal at the Larmor frequency there is a change of the transparency of the Cesium cell which is detected by the photocell. Thanks to the feedback the circuit oscillates naturally at the Larmor frequency which is proportional to the magnetic field. A filtered signal at the Larmor frequency is the output of this MAD.
