Detail of JJF(闽)1068-2015

Introduction of JJF(闽)1068-2015

Calibration specification for digital air flow hood 1 Scope This specification is applicable to the calibration of digital air flow hood (hereinafter referred to as air flow hood) with measuring range of (30 ~ 5000) m3/h. 2 Normative references The normative references of this specification are as follows: JJG 431-1986 Verification regulation of portable 3-cup anemometer Type DEM6 JJG 515-1987 Verification regulation of portable induction anemometer JJG 613-1989 Verification regulation of contact anemorumbometer JJF 1001 -2011 General terms in metrology and their definitions 3 Terms 3.1 air flow the amount of air in circulation per unit time, in m3/h 3.2 digital air flow hood an instrument that collects air flow to the speed equalizer on the base by using the air flow collecting hood, calculates the air flow value after measuring the air speed change value on the equalizer and the ventilation cross-sectional area of the base, and displays the air flow value directly through the digital display panel 3.3 air flow calibration fitting line the fitting line used to depict approximately or analogize the functional relationship between the measurement results of the air flow hood and the coordinates represented by the discrete point group of the air flow characteristic value on the plane 4 General Air flow hood is mainly used for air flow measurement. The working principle of the air flow hood is: measure the air speed by the air flow pressure sensor or thermal sensor on the end face of the base obtain, calculate the average value of the wind speed, and multiply the average value and the ventilation cross-sectional area of the base to get the air flow value. The air flow hood generally consists of a digital display panel, a nylon air hood, handles and a base (as shown in Figure 1). Figure 1 Schematic diagram for air flow hood 5 Metrological characteristics 5.1 Measurement error The air flow measurement error of the air flow hood is generally ± (3% ~ 10%) of the measuring range. 5.2 Appearance 5.2.1 All parts shall be installed correctly and firmly, the movable parts shall be flexible and reliable, and the nylon air hood shall be free of damage and leakage. 5.2.2 A nameplate shall be installed at an appropriate position, which should contain the following information: instrument name, model, end-of-manufacturing number, measurement range, measurement error, manufacturer or trademark, end-of-manufacturing date, etc. 5.2.3 The figures on the display panel shall be clear and complete, and the power supply interface, if any, shall be free of corrosion. 6 Calibration conditions 6.1 Environmental conditions a) Ambient temperature: (20 ± 5)°C; b) Relative humidity: (30% ~ 85%) RH; c) Atmospheric pressure: (950 ~ 1060) hPa.

Contents of JJF(闽)1068-2015

Introduction ii 1 Scope 2 Normative references 3 Terms 4 General 5 Metrological characteristics 5.1 Measurement error 5.2 Appearance 6 Calibration conditions 6.1 Environmental conditions 6.2 Power supply conditions 6.3 Air flow standard device 6.4 Other equipment 7 Calibration items and methods 7.1 Calibration items 7.2 Pre-calibration inspection 7.3 Calibration methods 8 Expression of calibration results 9 Re-calibration interval Annex A Example of inside page format for air flow hood calibration certificate Annex B Example of original record format for air flow hood calibration Annex C Example 1 of uncertainty evaluation Annex D Example 2 of uncertainty evaluation Annex E Calculation of the standard air flow value Annex F Fitting line equation and fitting line plot of indication - actual air flow value