JJF 1564-2016Calibration Specification for Temperature and Humidity Standard Chambers (English PDF)

3.1 Temperature and Humidity Standard Chamber

Specialized equipment used for the verification or calibration of temperature and humidity instruments; it generates a temperature and humidity environment meeting specific requirements within its valid working zone based on set parameters.

3.2 Valid Working Zone

The area within the temperature and humidity chamber used for the verification or calibration of temperature and humidity instruments.

3.3 Temperature Uniformity

The maximum absolute value of the temperature difference between any point in the surrounding area of the valid working zone and the center point at any instant within the 30-minute period after the temperature and humidity chamber has reached the specified stabilization time.

3.4 Humidity Uniformity

The maximum absolute value of the humidity difference between any point in the surrounding area of the valid working zone and the center point at any instant within the 30-minute period after the temperature and humidity chamber has reached the specified stabilization time.

3.5 Temperature Fluctuation

The range of the temperature at the center point of the valid working zone within the 30-minute period after the temperature and humidity chamber has reached the specified stabilization time (when expressed in "±" format, 1/2 of the range is used).

3.6 Humidity Fluctuation

The range of the humidity at the center point of the valid working zone within the 30-minute period after the temperature and humidity chamber has reached the specified stabilization time (when expressed in "±" format, 1/2 of the range is used).

3.7 Temperature Change Rate

The maximum value of the range within each 1-minute interval of the temperature at the center point of the valid working zone within the 30-minute period after the temperature and humidity chamber has reached the specified stabilization time; it is expressed in °C/min.

3.8 Humidity Change Rate

The maximum value of the range within each 1-minute interval of the humidity at the center point of the valid working zone within the 30-minute period after the temperature and humidity chamber has reached the specified stabilization time; it is expressed in %RH/min.

5.1 Temperature and Humidity Uniformity

For temperature and humidity chambers, temperature uniformity is generally no greater than 0.3°C, and humidity uniformity is generally no greater than 1.0%RH.

5.2 Temperature and Humidity Fluctuation

For temperature and humidity chambers, temperature fluctuation generally does not exceed ±0.2°C, and humidity fluctuation generally does not exceed ±0.8%RH.

5.3 Temperature and Humidity Change Rates

For temperature and humidity chambers, the temperature change rate is generally no greater than 0.2°C/min, and the humidity change rate is generally no greater than 0.8%RH/min.

NOTE. The above indicators are for reference only and are not used for determining compliance.

6.1 Environmental Conditions

6.1.1 Temperature. 15°C to 25°C; humidity. <=75%RH.

6.1.2 Temperature fluctuation shall not exceed ±3°C.

6.1.3 Environmental conditions shall also meet other requirements necessary for the normal

operation of the standard instruments and other auxiliary equipment used.

6.2 Measurement Standards and Other Equipment

6.2.1 Multi-channel temperature and humidity measurement device

6.2.1.1 Device configuration

The number of temperature and humidity sensors in the device shall meet the placement requirements; temperature and humidity sensors of the same model/specification shall be used for each channel; the device shall be equipped with an automatic recording function, and the minimum recording interval shall not exceed 20 s.

6.2.1.2 Technical indicators

The technical indicators for the temperature and humidity of each channel of the device are shown in Table 1.

Table 1 -- Multi-Channel Temperature and Humidity Measurement Device

7.1 Calibration Items

a) Temperature uniformity;

b) Humidity uniformity;

c) Temperature fluctuation;

d) Humidity fluctuation;

e) Temperature change rate;

The typical temperature calibration points are 15°C, 20°C, and 30°C; however, other calibration points may be selected based on user requirements. During calibration, temperatures shall be set in ascending order, and the temperature deviation at each calibration point shall be within ±0.5°C (based on the temperature at the center point). If the humidity function is enabled, the humidity set value is typically around 60%RH. Calibration items are generally performed under no-load conditions.

7.2.2.2 Temperature calibration procedures

Once the temperature and humidity chamber has reached the specified stabilization time, recording of temperatures at the various placement points begins; the recording interval is 20 s for the center point and 2 min for the other placement points. Ninety-one sets of data are recorded for the center point, and 16 sets of data are recorded for the other points. Data with a 20-second interval are denoted as T'i0 (i=1, 2, ..., 91), and data with a 2-minute interval are denoted as Tnj (n=1, 2, ..., 16; j=0, 1, ..., m-1), where m represents the number of placement points;

i and n represent the time indices (i stands for a 20-second interval, while n stands for a 2-minute interval); and j represents the index of the placement point location. If it is determined that the temperature and humidity within the chamber have reached equilibrium prior to the specified stabilization time, data recording may commence early.

The temperature stabilization time shall be in accordance with the instruction manual; if not specified therein, the following principle generally applies. if the change in temperature is 10°C or less, the stabilization time—measured from the setting of the temperature and humidity to the commencement of data recording—shall be 90 min; if the change in temperature is 5°C or less, the stabilization time shall be 60 min. Refer to Table 2 for the stabilization time at each calibration point.

Table 2 -- Stabilization Time

7.2.2.3 Temperature data processing

a) Temperature uniformity the maximum absolute value of the temperature difference (deltaTn) between the location of the center point and the locations of the other placement points at time n can be calculated using Formula (1).

Where.

deltaTn -- The maximum absolute value of the temperature difference between the location of the center point and the locations of the other placement points at time n, °C;

Where.

deltaTvk -- Temperature range within the kth minute, °C;

Ti0' -- The temperature value at the center point at time i, °C.

The temperature change rate (deltaTv) at a given temperature calibration point can be calculated using Formula (5).

Where. deltaTv -- Temperature change rate at a given temperature point, °C.

The maximum value of the temperature change rate (deltaTv) among the various temperature calibration points is taken as the temperature change rate of the temperature and humidity chamber.

7.2.3 Humidity calibration

7.2.3.1 Humidity calibration points

Humidity calibration is performed at 20°C at setpoints of 40%RH, 60%RH, and 80%RH; other calibration points may also be selected based on user requirements. During calibration, the humidity is adjusted from low to high levels; the humidity deviation at each calibration point must not exceed ±2.0%RH (based on the humidity at the center point). Humidity calibration may be performed simultaneously with temperature calibration.

7.2.3.2 Humidity calibration procedures

Once the temperature and humidity chamber has reached the specified stabilization time, recording of humidities at the various placement points begins; the recording interval is 20 s for the center point and 2 min for the other placement points. Ninety-one sets of data are recorded for the center point, and 16 sets of data are recorded for the other points. Data with a 20-second interval are denoted as Hi0' (i=1, 2, ..., 91), and data with a 2-minute interval are denoted as Hnj (n=1, 2, ..., 16; j=0, 1, ..., m-1), where m represents the number of placement points; i and n represent the time indices (i stands for a 20-second interval, while n stands for a 2-minute interval); and j represents the index of the placement point location. If it is determined that the temperature and humidity within the chamber have reached equilibrium prior to the specified stabilization time, data recording may commence early.

The humidity stabilization time shall be in accordance with the instruction manual; if not specified therein, the following principle generally applies. provided that the chamber temperature remains constant, if the change in humidity is 20%RH or less, the stabilization time—measured from the setting of the value to the commencement of data recording—shall be 60 min. Refer to Table 2 for the stabilization time at each calibration point.

7.2.3.3 Humidity data processing