Measuring modules (MM) for biomagnetic measuring systems: options

Model MM-5193-G  -  Twenty two channel (19 measuring channels + XYZ reference magnetometer) biomagnetic measuring module:

Description	MM-5193-G
Fiberglass Cryostat	LH-14,5-NTE
dc-SQUID-based measuring probes	Nineteen, second order gradiometer based
XYZ-magnetometer	yes
dc-SQUID electronics Unit	E1112-L, two boxes, (12 and 10 channels),
Control Unit ( ENSS included)	CU-322
DAS	24 bit, 22-channel
Connecting cables	One set
Software for module control	yes

Measuring module of the Model MM-5193-G can be used as a hardware of MCG- and MEG-systems. The module is based on the fiberglass cryostats of the Models LH-14,5-NTE. The diameters of the neck and the inner tail of the cryostat are equal to 150 mm and the time of complete helium evaporation is about 8 days.

19 measuring probes of signal channels are mounted on separated fiberglass tubes. They have diameters of 17 mm and form regular hexagonal structure with the distance of 30 mm between centers of probes. Each probe contains: the fine balanced 2-nd order gradiometer; the dc-SQUID-sensor and the cable for connection to the FLL-unit. The internal noise level of measuring probes is less than 10 fT/ÖHz.

XYZ reference magnetometer is integrated into the central measuring probe and located outside the area of signal gradiometers. Three dc-SQUIDs are mounted on the orthogonal surfaces of the 10 mm cube and produce the reference signals for the Electronic Noise Suppression System (ENSS).

The set of the electronics contains 22 similar digitally controlled FLL-channels and consists of two Units of dc-SQUID-electronics of the model E1112 and one Control Unit of the model CU-322.  The level of self-noise of channel's pre-amplifiers does not exceed 0.7 nV/ÖHz. Each FLL-channel has two ranges with respect to the feedback depth: 0.1V/F₀ and 1V/F₀. The bandwidth of the output signal in the closed feedback operation mode is 0-50 kHz at the -3 dB level, for a 0.1 F₀ signal.