User`s guide
M3000A/M3046A/M3015A/M3016A Service Guide
Introduction to the Instrument 1-35
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To ensure the safety of the patient, the patient-applied part is isolated from ground by opto-
couplers and a transformer. The circuit is also encapsulated in plastic.
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This illustration shows the block diagram of the Temp/Press circuit.
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The signals progress through the circuit as follows:
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This supplies 5V
DC
to a connected transducer. If a short circuit is detected by this circuit, the
CPU switches the voltage source off (to reduce power consumption).
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This provides protection for the rest of the circuit against defibrillator voltage, electrostatic
discharge, and any electromagnetic interference. The signal is passed on to the analog to
digital converter, and to the transducer detection circuit.
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The transducer being used can be determined by recognising the coding in the connector.
This is done by the transducer detection circuitry. A window comparator checks the input
voltages provided by the transducer against specified limits.
Excitation
Vo lt a g e
Transducer
Detection
Input Protection
Network
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Resistor
Array
Current
Source
A/D
Converter
CPU
ROM/RAM
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