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Correction of thermal gradient errors in stem thermocouple hygrometers
1Department of Botany, University of Georgia, Athens, Georgia 30602.
Plant Physiology
|January 1, 1979
Summary
This study shows that thermal gradients in stem thermocouple hygrometers directly impact measurements. Understanding these gradients is crucial for accurate water potential determination in plants.
Area of Science:
- Soil Science
- Plant Physiology
- Environmental Science
Background:
- Accurate water potential measurement is vital for understanding plant stress.
- Stem thermocouple hygrometers are common tools for this measurement.
- Thermal gradients can introduce errors in hygrometer readings.
Purpose of the Study:
- To investigate the effect of thermal gradients on stem thermocouple hygrometer accuracy.
- To quantify the relationship between thermal gradients and measured water potential.
- To establish correction factors for hygrometer readings.
Main Methods:
- Subjecting stem thermocouple hygrometers to transient and stable thermal gradients.
- Using reference solutions of NaCl.
- Measuring dew point and psychrometric voltages.
- Analyzing the relationship between voltages and zero offset voltages.
Main Results:
- Dew point and psychrometric voltages correlated with zero offset voltages, indicating thermal gradient influence.
- Measurement slopes varied with absolute temperature but not water potential.
- A consistent correction factor of 1.75 bars/microvolt was determined for one hygrometer between 20-30°C.
Conclusions:
- Thermal gradients significantly affect stem thermocouple hygrometer performance.
- Zero offset voltage is a key indicator of thermal gradient impact.
- Accurate water potential determination requires accounting for thermal gradients and applying appropriate corrections.
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