User`s guide

M3000A/M3046A/M3015A/M3016A Service Guide
Introduction to the Instrument 1-37
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The pressure/temperature measurement section of the CPU contains a serial bi-directional
data communication link to the pressure/temperature modules of the system CPU.
The following data is transmitted to the system CPU:
• Pressure wave
• Temperature numeric
• INOP and error messages
• Status messages
The following data is received from the CPU:
• Control messages
All messages in both directions are secured by checksums.
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The data exchange between the A/D converter and the CPU is based on a serial
communication link. The calibration information is periodically refreshed to ensure proper
operation of the converter. The converter generates an interrupt each time new data is
available. This forces the CPU to retrieve the data and to calculate the scaled pressure
waveform of temperature value.
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3UHVVXUHPHDVXUHPHQW Data from the A/D converter is sent to a single-pole digital filter
which generates the specified frequency response. Additionally, the transducer zero value is
subtracted from the signal.
7HPSHUDWXUHPHDVXUHPHQW This is referenced against a high-precision calibration resistor.
Pressure / Temperature
ADC
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System
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Mode Detector
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Controller &
Data Acquisition
Wave Processing
&
Filtering
CPU
Communication