Digital superconducting quantum interference devices (SQUIDs) have been proposed to extend the dynamic range of analog SQUIDs whenever magnetic fields varying in a wide range need to be measured. We developed a digital SQUID concept, based on the single flux quantum technique, using the reliable 1 kA/cm2
niobium trilayer technology of the FLUXONICS Foundry. We present an extensive experimental analysis to evaluate the digital SQUID magnetometer operation in shielded and unshielded conditions. Bit error rate measurements have shown reliable operation of the digital superconducting circuitry with operation margins of ±11%
, confirmed by stable operation in unshielded magnetometer mode for more than 10 h. The best intrinsic magnetic field resolution, corresponding to one magnetic single flux quantum (Φ0)
, was found to be about 4.2 nT. Peak-to-peak amplitudes of 14 800
and 2810 flux quanta Φ0
could be measured, respectively, for inductively coupled current and magnetic field inputs. A flux noise level of 220 mΦ0/
at 0.1 Hz has been measured, corresponding to a dynamic range of 76 dB (e.g., above 12 bits). Furthermore, preliminary experiments have shown that the integration of a digital SQUID with an analog dc SQUID in a hybrid magnetometer is a solution to reach simultaneously a high dynamic range and an increased field sensitivity. Such a device is of utmost importance to detect magnetic fields with high dynamic range to monitor earthquakes in the presence of high amplitude external magnetic perturbations.