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Galvanic Isolation Guidelines for MP Research Systems

MP160 and MP150 data acquisition systems incorporate staggered sections of isolation: Primary (mains power) isolation is provided by an external IEC60601-1 specified power supply (AC150A); Secondary isolation is provided by high isolation DC-DC converters, optical isolators and Ethernet transformers within the units.

Galvanic isolation is used where two or more electric circuits must communicate, but their grounds may be at different potentials. Galvanic isolation is an effective method of breaking ground loops by preventing unwanted current from flowing between two units sharing a ground conductor.

Galvanic isolation is also used for safety, preventing accidental current from reaching ground through a person’s body.

The attachable Conditioning Modules (such as UIM100C, ECG100C, etc.) operate at Safety Extra-Low Voltage.  This SELV power is provided by the secondary isolated section of the MP unit.  Subjects are galvanically tied to this SELV isolated ground, when biopotential amplifiers are used.

Subject isolation from power mains is provided by the external power supply (wall transformer adapter) and subsequently by the MP unit’s internal DC/DC converter, optocouplers and Ethernet transformer.

As a general laboratory instrument, the MP System can be used to monitor signals from various laboratory equipment or, alternatively, live subjects. Because of the MP system construction, it is possible to inadvertently ground the subject when connecting other laboratory equipment to the system during subject monitoring.

WHEN MEASURING FROM SUBJECTS, DO NOT HAVE ANY OTHER LABORATORY EQUIPMENT CONNECTED TO THE MP SYSTEM’S ANALOG OR DIGITAL INPUT or OUTPUT PORTS, WITHOUT USING SUITABLE BIOPAC ISOLATION INPUT OR OUTPUT DEVICES.

The MP System Analog/Digital ports (and UIM100 and all other Conditioning Modules) are part of the subject isolation circuit and thus can become accessible metal parts that may be incidentally grounded which would defeat the isolation provided by the internal DC to DC converter, optocouplers, and Ethernet transformer.

When connecting the MP system, via Conditioning Modules, to a subject, safety concerns dictate the removal of all galvanic connections from other mains powered or earthed equipment from the UIM100 module or other Conditioning Modules.

If signal connections to other mains powered or earthed equipment are required while recording from subjects using the MP system, then those connections should be made via signal isolator INISOA/INISO or OUTISOA/OUTISO in conjunction with an AMI100D or HLT100C module. In the case of computer connections for stimulus presentation synchronization, use the STP100C.

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