1. Full Chinese display, easy operation: Full Chinese display, aesthetically pleasing interface: Utilizes a high-resolution LCD display module. All data, statuses, and operation prompts are displayed in Chinese, completely eliminating manufacturer-specific symbols or codes. Simple menu structure, text-based human-machine dialogue: Compared to traditional instruments, the OXY5402A offers many additional functions. However, thanks to its categorized menu structure and computer-like operation method, it is clearer and more convenient to use. There is no need to memorize operation steps or sequences; users can operate it by following on-screen prompts without referring to the manual. Multi-parameter simultaneous display: Displays oxygen concentration value, input or output current, temperature, time, and status simultaneously on one screen. The main display shows the oxygen concentration value in a 10×10mm format, making it eye-catching and visible from a distance. Six sub-displays show input or output current, temperature, status, day of the week, year, month, day, hour, minute, and second in a 5×5 format to meet different user habits and provide a time reference for the instrument. 2. Practical function groups: Historical curve function: The secondary instrument automatically stores the measured oxygen concentration value every five minutes and can continuously store data for one month. The "historical curve" provides an overall reflection of water quality trends and processes, which is highly beneficial for identifying and resolving issues. The "timed and fixed-point" function retrieves the measured oxygen concentration and temperature values at specific points and times. Notebook function: Faithfully records the instrument's operation usage and alarm occurrence times for easy management. Electrode research function: Stores the method, time, and results of 50 calibrations to analyze the electrode's variation patterns. Digital clock function: Displays the current time, providing a time reference for digital recording functions. Backlight function: Can be used in dimly lit or completely dark environments. Automatically adjusts contrast based on temperature changes, or can be manually adjusted to ensure the display remains clear. Industrial control watchdog: Ensures the instrument does not freeze, which is a basic requirement for online instruments. Output current setting and checking function: Manual current source function allows checking and arbitrarily setting output current values, facilitating the inspection of recorders and lower-level machines. Software-set current output mode: Software selection for 0–10 mA or 4–20 mA output without requiring users to toggle any switches. Four calibration methods: In addition to traditional one-point and two-point calibration methods, manual input of zero point and slope, as well as calibration using known oxygen concentration values, are available to meet various usage scenarios. Symbols and Terminology When using the OXY5402A instrument, you may encounter some new terms and concepts, which are explained below: Pa and bar are both units of atmospheric pressure. 1 bar = 10? Pa, 1 mbar = 100 Pa = 1 hPa. I?: In this manual and on the display screen, I? represents the current when the oxygen concentration is zero (similar to the zero potential of a pH electrode), but it is relatively stable. S: In this manual and on the display screen, S represents the slope of the oxygen electrode. The unit is pA/mbar, and it is a negative value, typically ranging from -200 to -600 pA/mbar. Technical Specifications 1. Standard: JJG 291-1999 "Film-Covered Electrode Dissolved Oxygen Analyzer"; 2. Chinese LCD display, Chinese menu-based operation; 3. Measurement range: 0–100.0 μg/L; 0–20.00 mg/L (auto-switching); 0–60°C; Saturation: 0–200.0%; (Press the "Confirm" key during measurement to switch between dissolved oxygen concentration value and saturation display) Resolution: 0.1 μg/L, 0.01 mg/L, 0.1°C; 0.1%; 4. Basic instrument error: μg/L: ±1.0% FS; mg/L: ±0.5% FS; temperature: ±0.5°C; 5. Instrument repeatability: ±0.5% FS; 6. Instrument stability: ±1.0% FS; 7. Automatic temperature compensation range: 0–60°C, with 25°C as the reference; 8. Response time: <60 seconds (98% of final value, 25°C); 37°C: 98% of final value <20 seconds; 9. Clock accuracy: ±1 minute/month; 10. Output current error: ≤±1.0% FS; 11. Isolated output: 0–10 mA (load resistance <1.5 kΩ); 4–20 mA (load resistance <750 Ω); 12. RS485 communication interface (optional); 13. Data storage capacity: 1 month (1 point/5 minutes); 14. Continuous data retention time after power loss: 10 years; 15. Alarm relay: AC220V, 3A; 16. Power supply: 220V ±10%, 50 ±1 Hz; DC24V optional (specify when ordering); 17. Dimensions: Secondary instrument: 146 (L) × 146 (W) × 108 (D) mm; panel cutout: 138 × 138 mm; 18. Weight: Secondary instrument: 0.8 kg; 19. Operating conditions: Ambient temperature: 0–60°C; relative humidity: <85%; 20. Inlet and outlet connection pipes: Hard or soft pipes, available in three outer diameters: ?8, ?10, ?12. Typically, hard pipes of ?10 are provided for easy welding and sealing.