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Dedicated electronics for fixed points furnaces control

New Heat Pipes for temperature fixed points. Dedicated electronics for fixed points furnaces control. “New electronics and new Heat Pipes for fixed points ”. Istituto Nazionale di Ricerca Metrologi c a. Noise. For simplicity we can distinguish two sources of noise:.

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Dedicated electronics for fixed points furnaces control

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  1. New Heat Pipes for temperature fixed points Dedicated electronics for fixed points furnaces control “New electronics and new Heat Pipes for fixed points” Istituto Nazionale di Ricerca Metrologica

  2. Noise For simplicity we can distinguish two sources of noise: • Noise caused by internal disturbs of the system • These disturbs are, in general, continous and periodic in time • Noise caused by external disturbs • These disturbs are, in general, discontinous, accidental and random in time

  3. Internal disturbs • Disturbs in ingress of the control system given directly by the action of thermocouples • Problems operating on the system control subsequent to the level of the components that generate the parameters • Magnetic noise produced also by the power supply • Dirsturbs acting on the sensible element that have to be measured given by the furnaces • Problems caused by disturbs resulting by the ground reference loop

  4. External disturbs • External electromagnetic influences due to humans (for exemple with the use of cellular telephone) due to other instruments in the lab • Mechanical disturbs produced by humans produced by mechanical vibrations • Capacitative induced effects given by external effects (vibrations again)

  5. Lots of noises! • Thermal noise Thermal noise is caused by the thermal agitation of charge carriers in a conductor. • Burst noise also called popcorn noise, appears to be related to imperfections in semiconductor material and heavy ion implants. • Flicker noise Flicker noise is also called 1/f noise. It is present in all active devices that work with low frequency signals and has various origins. Flicker noise is always associated with a DC current, so it is the main noise internal cause. • Drift Temperature, ageing and packaging stress cause time-varying offset

  6. RF and elettromagnetic interference • Magnetic field generated by current flowing in ac power supply at 50 Hz • Spikes of voltage by any near device Noise sources affecting thermocouples

  7. Characterized by •Offset •Drift •1/fnoise •PSRR, CMRR reduction Amplifier behaviour near DC

  8. Offset and 1/f noise are “inside” the system • But we can reduce the offset “enough” by • 1.Using “large” devices and good layout • 2.Dynamic offset-cancellation (DOC) techniques • DOC techniques also reduce 1/f noise!

  9. DOC Techniques Frequently chopping is significantly better than auto-zeroing

  10. Existing electronic made at INRiM • A CT 9001 and a CT 9000 modules for • - conditioning thermocouple signal • - reset possible drift • - fine temperature control • An Euroterm commercial controller module is then used to control the power supplied to the furnace

  11. CT 9000 is an amplifier module that amplifies the signal from thermocouple with a x10, x100, x1000 gain. It is possible a check zero to see the presence of offset and drift. Moreover, it is possible to add to output signal of this module an offset signal EΔ, adjustable in the first fine regulation (±10k) with 2k/cursor number; in ultra-fine regulation, for each number it is possible to adjust of 0.2k/cursor step. For second fine regulation (±2.5k) it is possible to adjust at 0.5k/cursor number and in ultra-fine regulation, for each number it is possible to adjust at 0.05k/step level. CT9000

  12. CT9001 The module CT 9001 is used to adjust possible offsets and drift from thermocouple and from the CT 9000

  13. Actions • Design of temperature controller • Implementation of micro-controller inside software • Realization of the system • Performances evaluation

  14. Specifications • Temperature control • fine • wide • I/O devices • Parameters setting • Data visualization • Remote PC control

  15. Software • Thermocouple output voltage is amplified by a low noise amplifier (LNA), converted in a digital signal and sent to the micro-controller. • The micro-controller compares the voltage/temperature value with a reference value and supply the power in the furnace with the pulse width modulation (PWM) technique

  16. PWM Power control PWM (Pulse Width Modulation ) is a technique that modules a wave squares varying duty cycle of them.

  17. Software The software will be developed in order to reach the complete control of the electronics, I/O interfacing and routines. It allows to set the specific requirements by selecting: • Type of input sensor and temperature range • Control algorithm needed (PID) • Number and type of outputs (heat, cool, alarm,) • Scale of application, set points, alarm points.

  18. A firmware, made of several functions, will be written and loaded in the memory inside of micro-controller to satisfy the required specifications. These functions can be called both by on board keyboard and from a PC. Data can be saved and on line graphs can be obtained.

  19. Heat Pipes and GCHPs

  20. Temperature stability in a mercury GCHP

  21. Temperature uniformity in a mercury GCHP

  22. Fine controlled temperature changes

  23. The first Gas Controlled Heat Pipe for fixed points

  24. We thank you!

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