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Part Number: OPA4188
I try to build a thermocouple design. My aim is to detect the range of -200C to +600 C. While I search convenient components to use in cold junction compensator and precision zero drift amplifier for output. Could you advise a design and components to achieve the range by details.
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In reply to Thomas Kuehl:
Thank you for your answer. TIPD120 is convenient for thermocouple ? Can I connect directly ? If I do, how can I connect thermocouple to design ? Or How can I enhance temperature range of TIPD209 from -200C to +600C?
Have a nice day
In reply to Yildirim:
Since TIPD120 was developed around an RTD the circuit wouldn't be directly applicable to a thermocouple. The RTD has much lower output voltage change for a change in temperature than the thermocouple. Also, the RTD requires current excitiation to develop a measurable voltage while the thermocouple doesn't. It produces a voltage output in reponse to a temperature differential.
Certainly the TIPD120 amplifier and delta-sigma converter could be employed to convert the thermocouple voltage to a digital equivalent. However, because the thermocouple linearity isn't ideal some method must be employed to correct for nonlinearlty over temperature if accurate results are needed; especially below 0 °C. The type-K thermocouple provides about the best linearity across temperature of the various types available, but the cold non-linearity will likely be an issue.
The TIPD209 design is optimized for the temperature range of -50 °C to 500 °C. I suspect this narrower temperature range was selected to capitalize on a more linear portion of thermocouple's temperature range, and to maximize the cold-junction compensation accuracy. If one is willing to tolerate the higher non-linearity across temperature, then the TIPD209 circuit could be modified for a wider temperature range. The instrumentation amplifier gain and reference voltage applied to the INA188 would need to adjusted to accommodate the voltage range produced by the thermocouple.
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