JJG 1094-2013Water Quality On-line Analyzers of Total Phosphorus and Total Nitrogen (English PDF)

5.3.5 Stability

After instrument calibration, use 50% measuring range standard solution to measure;

record initial measured value; then measure once per hour; measure for 24 h continuously;

record the instrument measured values; calculate stability of the instrument based on

Formula (4).

Where,

- Instrument stability;

- Measured value per hour, mg/L;

- Initial measured value, mg/L.

5.3.6 Safety performance

5.3.6.1 Insulation resistance

Power plug is not connected to power grid; power switch is at on-position; use insulation resistance meter to apply 500 V DC test voltage between power incoming line and enclosure; measure insulation resistance after being stabilized for 5 s.

5.3.6.2 Dielectric strength

Power plug is not connected to power grid; power switch of instrument is at on-position;

apply test voltage between power incoming line and enclosure through withstanding voltage tester; test voltage gradually rises to 1.5 kV; maintains for 1 min to observe whether there is flashover and breakdown phenomena; then gradually drop to zero.

5.3.6.3 Leakage current

Power plug is connected to power grid; power switch is at on-position; leakage current tester is connected to between instrument enclosure and power incoming line. Adjust the voltage of leakage current tester to 242 V and measure once; change power polarity and

Annex A

Preparation of standard solution

A.1 Zero calibration solution of total phosphorus

Use distilled water or pure water that meets analysis laboratory Grade 2 water requirements.

A.2 Zero calibration solution of total nitrogen

Zero calibration solution of total nitrogen shall be non-ammonia water, which is prepared through one of following methods.

a) Ion exchange method. Make distilled water to pass through strong acid cation exchange resin (hydrogen form) column; the effluent is collected in a glass bottle sealed with glass lid.

b) Distillation method. Add 0.1mL of sulfuric acid (A. R. rho= 1.84 g/mL) into 1 000 mL of distilled water. Redistill it at all-glass distiller; discard the initial 50 mL of distillate;

the remaining distillate is collected in a glass bottle sealed with glass lid.

A.3 Preparation of total phosphorus standard solution

Prepare standard solution of total phosphorus for verification based on concentration of standard solution of total phosphorus for verification in accordance with concentration of standard solution of total phosphorus for verification, amount and concentration of standard solution of total phosphorus in water. For example, accurately pipette 20 mL of total phosphorus constituent analysis standard solution of which the mass concentration is

500 mg/L; place in a 1 000 mL volumetric flask; use A.1 total phosphorus zero calibration solution to dilute to the mark; set the volume and shake well. That is the 1 L of total phosphorus standard solution of which the mass concentration is 10.0 mg/L. Standard solution of total phosphorus shall be prepared when it is needed.

A.4 Preparation of total nitrogen standard solution

Prepare the standard solution of total nitrogen for verification based on concentration of standard solution of total nitrogen for verification in accordance with concentration of standard solution of total nitrogen for verification, amount and the concentration of standard solution of total nitrogen in water. For example, accurately pipette 20 mL of total nitrogen constituent analysis standard solution of which the mass concentration is 500 mg/L; place in a 1 000 mL volumetric flask; use A.1 total nitrogen zero calibration solution to dilute to the mark; set the volume and shake well; That is the 1 L of standard solution of total nitro...

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