Hybrid Circuit Design for Down Hole Sensors

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Hybrid Circuit Design for Down Hole Sensors

• Stephen Pondelik
• The University of Tulsa
• Richard Kriege
• Geophysical Research Company

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Introduction

• Goal- Create a hybrid circuit that contains 3
  pierce type oscillators.
• Application- Circuit will be used down hole with
  heat exceeding 150 degrees Celsius to measure
  pressure and temperature.
• Plan- Test various oscillator types by exposing
  them to various temperatures and observing heat
  characteristics.

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Hybrid Overview

• Circuit that is placed on a ceramic substrate
• Dissipates heat at a higher rate
• Silver or gold strands connect parts
• Extremely small
• Higher functioning temperature

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The Oscillator Designs

• There are two oscillator designs that are being
  considered, the ESP and the Integra. Both of
  which have varying characteristics that will help
  determine which is to be used.

• ESP
• Thru-hole parts
• Discrete Components
• Oscillates due to an transistor

• Integra
• Surface mount parts
• ICs and Discrete parts
• Oscillates due to an inverter

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The Oscillation

• Consists of three oscillators that interact with
  each other
• Based on the resonant frequency of a specially
  constructed quartz crystal
• Reference oscillator does not change frequency
• Temperature oscillator changes with temperature
  linearly
• Pressure oscillator changes with pressure
  parabolically

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Circuit Testing

• Low heat testing
• 100-350 degrees Fahrenheit range
• Observe temperature/pressure frequency throughout
  test
• Observe current change throughout test
• Circuit must maintain the ability to turn on and
  off

• High heat testing
• 350-400 degrees Celsius
• Observe temperature/pressure frequency throughout
  test
• Observe current change throughout test
• Circuit must maintain the ability to turn on and
  off
• Observe delay of oscillators output waveform

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Final Application

• Which circuit to chose?
• Lowest current consumption leads to longer
  battery life
• Accurate temperature and pressure frequency leads
  to accurate down hole readings
• Ability to turn on and off at high temperatures
  provides functionality
• Delay to determine oscillator's response time
• No egregious failures
• These factors will determine which circuit to use
  in the hybrid design

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Our Sponsors

• Geophysical Research Company, LLC
• The University of Tulsa
• Oklahoma Center for the Advancement of Science
  and Technology