Conductivity Meter User Manual

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I. Instrument Features 　　1. The instrument utilizes high-performance integrated circuits to create a sine wave generator with stable performance; as a result, the display is stable and there is minimal drift； 　　2. The instrument employs a phase-sensitive detector, which suppresses the effect of the distributed capacitance of the electrode leads on the measurements. As a result, this instrument does not require a capacitive compensation regulator; it features automatic shift compensation and can measure low conductivity values ； 　　3. The frequency and range of the instrument’s signal source can be switched synchronously, ensuring ease of use ； 　　4. The instrument can directly read conductivity across the entire range; only the electrode constant needs to be calibrated once, making it extremely convenient to use ； 　　5. The instrument is equipped with a thermal feedback circuit and a dehumidifying element, ensuring its operation is not affected by temperature and humidity ； 　　6. The instrument is equipped with a temperature compensator; the DDS-11C model can provide a standard temperature compensation of 2% for the liquid being measured, while the DDS-307 model offers compensation ranging from 1% to 4%. II. Main Technical Specifications 1. Measurement range: See (Table 3) 2. Accuracy class: Class 1 (→Table 4) 3. Meter accuracy: ≤F.S±1.0% plus or minus 1 digit ； 　　4. Basic error of the instrument: ≤F.S±1.5% ； 　　5. Constant compensator: ≤F.S±1.0% ； 　　6. Temperature compensator: ≤F.S±1.0% ； 　　7. The electrical conductivity increases as the temperature rises: 2% per degree for the DDS-11C model, and 1–4% per degree for the DDS-307 model. 8. Instrument repeatability: not more than one-third of the basic error ； 　　9. Instrument stability: The drift within 3 hours shall not exceed 2/3 of the basic error. 10. Operating conditions: 　　　⑴. Ambient temperature: 5℃～35℃ ； 　　　　⑵Relative humidity: ≤80% ； 　　　　⑶Power supply: AC 220V±22V, Hz 50±1Hz. III. Use of the instrument: 1. Plug the power cord into a socket with reliable grounding ； 　　2. Set the selector switch to the calibration position, and turn on the device to preheat for 10–15 minutes ； 　　3. Measurement of conductivity: (1) When the instrument is used across its full range, it is sufficient to calibrate the electrode constant only at the third range or any other range; the maximum number of valid readings is preferred. 　　　 (2) Set the temperature compensator at 25°C, the temperature value for standard conductivity. 　　　 (3) Set the electrode selection switch of type DDS-307 to corresponding positions such as 1 or 0.1. Set the selector switch to the calibration position, and adjust the constant regulator so that the instrument displays the electrode constant value of the electrode being used. Example: If the constant of the electrode is 0.87, then adjust the constant regulator so that the instrument displays 0.870 (870). 　　　 (4) Insert the electrode plug into the socket, then immerse the electrode in the solution to be tested. 　　　 (5) Set the selector switch to the conductivity position, then choose an appropriate range (the range selector should be adjusted gradually from range 4 to ranges 3, 2, and 1) so that the instrument displays as many significant digits as possible. Do not turn the temperature compensator; the instrument will display the actual conductivity of the liquid at its current temperature. If the instrument shows “1” (indicating that the value is outside the measurement range), use a conductivity electrode with a constant of 10 (0.1). When in use, apply the time constant correction and multiply the digital display value by 10 (0.1). 　　　 (6) The DDS-307 and DDS-11C models are equipped with temperature compensators; adjust the temperature compensator to the actual temperature of the liquid being measured, and the instrument will display the standard conductivity at 25°C. 　IV. Precautions 　　1. For precautions regarding the use of electrodes, please refer to the electrode manual. 　　2. The leads and plugs of the electrodes should be kept dry to reduce contact resistance. 　　3. Pure water should be measured while in flow, and clean containers should be used. 　　4. During the measurement process, if it is necessary to recalibrate the instrument, simply set the selection switch to the calibration position to recalibrate it. There is no need to unplug the electrode connectors or remove the electrodes from the solution being measured. 　　5. When the instrument is not in use, the power plug must be removed to protect it. V. Completeness of the equipment 1. One conductivity meter 2. One set of instructions for use 3. One product certification certificate 4. One DJS-1 conductivity electrode (air plug) 5. DJS-0.1 and DJS-10 conductivity electrodes to be purchased separately. Appendix: For precise determination of the electrode constant J, see (Tables 2 and 4). Table 4 shows the conductivity values (K values) of KCl solutions at various concentrations and temperatures. The determination of the electrode constant is done by using a solution with a known conductivity; its specific conductance G is measured, and then the value of J is calculated by dividing K by G. 　　Example: At 25°C, the conductivity of a solution with a concentration of 0.01 N KCl in a conductivity cell was measured to be 1487 μS. From the table, the conductivity of a 0.01 N KCl solution at 25°C is 0.001413 Scm-1. Thus, the constant for this electrode is 1413÷1487=0.95 cm-1. 　　(S/cm = 10³ ms/cm = 10⁶ μS/cm = 10⁹ ns/cm) When the instrument is set to measure conductivity, the electrode with an unknown constant is inserted into a solution with a known conductivity. The constant correction knob is turned so that the instrument displays the conductivity value of the known solution; once the switch is switched to the correction mode, the instrument shows the constant of the unknown electrode. Table 1: Conductivity and suitable conductivity electrodes
Range | Conductivity (S/cm) | Resistance (Ω·cm) | Signal frequency (Hz) | Suitable electrode | Electrode constant
1* | 0–0.2 μS/cm | 0–20 MΩ·cm | 100 | DJS-0.1 | 0.1
1 | 0–2 μS/cm | 0–2 MΩ·cm | 100 | DJS-0.1 | 0.1
2 | 0–20 μS/cm | 0–200 KΩ·cm | 100 | DJS-1, Bright 1 | –
3 | 0–200 μS/cm | 0–20 KΩ·cm | 100 | DJS-1, Platinum black 1 | –
4 | 0–20 mS/cm | 0–20 KΩ·cm | 1000 | DJS-1, Platinum black 1 | –
5 | 0–20 mS/cm | 0–20 Ω·cm | 1000 | DJS-10 | 10
5* | 0–200 mS/cm | 0–20 Ω·cm | 1000 | DJS-10 | 10