A CALIBRATOR SYSTEM FOR DEW POINT TEMPERATURE SENSORS OF GAS NEAR THE SATURATION VAPOR POINT

• Main Author: Sindhu Tistomo, Arfan
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87429
• Institution: Institut Teknologi Bandung

It has been proven that humidity is highly beneficial in various fields. For example, humidity affects the quality of poultry egg embryos, the stability of medicines, metal corrosion, and room comfort. There are various types of humidity measuring instruments, or hygrometers. Based on their measurement methods, hygrometers can be divided into two types: hygrometers with direct measurement methods and hygrometers with indirect measurement methods. The direct measurement method refers to hygrometers that measure humidityrelated parameters directly, such as relative humidity and dew point temperature. Examples of hygrometers using this method include electronic hygrometers, hair hygrometers, and dew-point hygrometers (chilled mirror hygrometers/CMH). Meanwhile, hygrometers with an indirect measurement method measure humidityrelated parameters through temperature sensors, pressure sensors, or other sensors. Examples of this type of hygrometer include psychrometers and humidity generators. Accurate humidity measurement can be ensured if the hygrometer used is traceable to the International System of Units (SI units). To be traceable, the hygrometer must be calibrated. Generally, calibration involves comparing the readings of two instruments, one of which is a reference or standard, often called a calibrator. The calibrator must have higher accuracy than the instrument being calibrated. For hygrometers, the pinnacle of traceability is the humidity generator. This research aims to establish hygrometer traceability by providing a calibrator system for dew point temperature sensors of gas near the vapor saturation point, also known as a dew-point generator (DPG). This standard will complement the existing humidity generator, the commercial humidity generator 2500 ST made by Thunder Scientific. Unlike the 2500 ST, which operates on the two-pressure (2P) principle, the system developed operates on the single-temperature (1-T) principle. The gas supplied by the gas pump is saturated in a saturator chamber submerged in a water bath with controlled temperature. Consequently, the resulting dew point temperature will be equal to or close to the saturator temperature. The novelty of this system is the use of a commercial micro-bubble aerator for the saturation process. The micro-bubble aerator is connected to a coil-shaped heatexchanger with a diameter of 15 cm, made of stainless steel pipe with a diameter of 10 mm and a length of 6 m. Heating the gas outlet pipe 25°C higher than the water bath temperature starts approximately 5 cm below the water surface. This aims to eliminate the influence of ambient temperature when the pipe emerging above the water surface gets longer due to the lowering of the water surface level caused by evaporation. The combination of the bubble aerator with PID (Proportional Integral Derivative)-based temperature control accelerates the thermodynamic equilibrium between air/gas and water in the saturator, achieving saturator efficiency of near or equal to 100%. This research includes three studies: Determination of the uncertainty of the water vapor saturation pressure formula formulated by Koutsoyiannis, modeling and simulation of dew point temperature generated by a bubble aerator, and characterization of the DPG. The first study involves deriving the formulation based on statistical mechanics and its implementation in measuring relative humidity and dew point temperature by the 2500 ST humidity generator. The result of this study is that the uncertainty of the Koutsoyiannis formulation is better than the Magnus formulation, with a value of 0.1% in the temperature range of -12°C to 50°C. The second study implements the Monte Carlo method involving random numbers with a specific distribution. Based on the bubble diameter measurement data, the bubble velocity can be determined. This bubble velocity is related to the heat transfer between the bubbles and water in the saturator during the saturation process. Assuming the dew point temperature equals the bubble temperature when it leaves the water surface, the results obtained are satisfactory in experiments. The third study is the characterization of the DPG. The first step is to compare its dew point temperature with the CMH model 473 made by MBW. The second step is to trace the DPG with the reference value from the Asia Pacific Metrology Program (APMP.T-K8) regional comparison test Dew Point Temperature +30°C to +95°C to determine its accuracy. The results indicate that the saturator efficiency is 100%, and the DPG accuracy is ±0.07°C. The research was conducted at the SNSU-BSN temperature laboratory, Puspiptek Complex, Building 420 Setu, South Tangerang 15314, and ITB Bandung campus.