| Zugriffsnummer | 30372 |
| Dokumenttyp | Zeitschriftenartikel |
| Sprache | Englisch |
| Titel | A 5‐MHz bandwidth SQUID magnetometer with additional positive feedback |
| Autor(in); Institution |
Drung, Dietmar; 9.33, Kryoelektronik, PTB-Berlin
Matz, Hartmut; 10.23, Druck- und Strömungsmessung in der Medizin, PTB-Berlin
Koch, Hans; 9.33, Kryoelektronik, PTB-Berlin
|
| Quelle/Jahr | Review of Scientific Instruments: 66 (1995), 4, 3008 - 3015 |
| ISSN | 0034-6748 (PRINT) ; 1089-7623 (ONLINE) |
| DOI | |
| Verlag | Melville, NY: AIP |
| Freie Schlagworte | superconducting quantum interference devices ; 1/f noise |
| Zusammenfassung | A fast SQUID(superconducting quantum interference device) magnetometer system using the latest multiloop magnetometer W7A with additional positive feedback has been built. A 3‐dB bandwidth of 5 MHz has been achieved in a simple direct‐coupled flux‐locked loop. The feedback range is ±620 Φ0 or ±290 nT, the white‐noise level 3.4×10-6 Φ0/√Hz or 1.6 fT/√Hz, and the 1/ f corner frequency ≂7 Hz. Above 1 MHz the noise level increases slightly, approximately with √S Φ αf1/6. At high signal frequencies a slew rate of about 8×105 Φ0/s has been measured. Below the pole frequency of the second integrator (480 kHz) the slew rate increases with decreasing frequency, having a maximum of 3×107 Φ0/s at 7.6 kHz. The total harmonic distortion (THD) decreases strongly with the signal amplitude below the slew rate limit. For a sinusoidal signal with half the maximum amplitude, the THD is ≂4% at 1 MHz, ≂0.04% at 100 kHz, and ≂2.7 ppm (1 ppm=10−6) at 10 kHz. Below about 2 kHz the THD becomes almost frequency independent and lies between 0.4 and 7 ppm for signal amplitudes between 2.5 and 620 Φ0. |
