The DDS-421 is a full-featured benchtop conductivity meter with a 7-inch color TFT touchscreen, measuring conductivity (0.05 μS/cm to 500.0 mS/cm), resistivity, TDS, salinity and temperature. Features three-level user management, 1500-point data storage, GLP printing and USB/RS232 connectivity. Supplied with DJS-1N conductivity electrode and T-820D temperature probe.
The DDS-421 benchtop conductivity meter is a comprehensive multiparameter instrument designed for demanding laboratory and industrial measurement applications. Built around a 7-inch color TFT touchscreen with Metro-style interface, it measures five parameters simultaneously — conductivity, resistivity, TDS (total dissolved solids), salinity and temperature — making it a versatile single-instrument solution for water quality analysis, environmental monitoring, pharmaceutical water testing and industrial process control.
With a wide conductivity measurement range of 0.05 μS/cm to 500.0 mS/cm and automatic frequency and range switching, the DDS-421 handles everything from ultrapure water to concentrated solutions without manual adjustment. Auto temperature compensation from -5.0°C to 110.0°C via the included T-820D probe ensures accurate readings across varying sample conditions.
As the flagship benchtop conductivity model in the Skill Scientific range, the DDS-421 includes three-level user management (Administrator / User / Visitor) — a feature unique to this model within the DDS series. Combined with 1500-point data storage, GLP-compliant printing and USB/RS232 connectivity, it is well suited to regulated environments including pharmaceutical QC, environmental compliance testing and multi-operator laboratory settings.
| Model | DDS-421 | |
| Measuring Range | Conductivity | 0.05 μS/cm – 500.0 mS/cm |
| Resistivity | 5.00 Ω·cm – 20.00 MΩ·cm | |
| TDS | 0.000 mg/L – 100 g/L | |
| Salinity | 0.00 – 8.00 % | |
| Temperature | -5.0 ~ 110.0 °C | |
| Accuracy (±) | Conductivity | ±0.5% FS |
| Resistivity | ±0.5% FS | |
| TDS | ±0.5% FS | |
| Salinity | ±0.1% | |
| Temperature | ±0.2 °C | |
| Included Sensor | DJS-1N (black) + T-820D | |
| Optional Sensors | DJS-0.01 / DJS-0.1 / DJS-1 (bright) / DJS-10 | |
| Electrode Connector | BNC / RCA | |
| Display | 7″ Color TFT Touchscreen | |
| Electrode Holder | Included | |
| Temperature Compensation | (-5.0 ~ 110.0) °C Auto / Manual | |
| Calibration | 1–3 point standard solution / Electrode constant | |
| Standard Solutions | 146.5 μS/cm / 1408.3 μS/cm / 12.852 mS/cm / 111.31 mS/cm | |
| Data Storage | 1500 data points | |
| Connectivity | USB + RS232 | |
| Printing | GLP-compliant format | |
| User Management | Password protected, 3 levels | |
| Date / Time | Yes | |
| Prompt Tone | On / Off | |
| Power Supply | DC 12V | |
| Operating Temperature | 5°C ~ 40°C | |
| Relative Humidity | ≤80% | |
| Dimensions (mm) | Approx. 200 × 130 × 60 mm | |
| Weight (kg) | 1 | |
Both models share the same measurement specifications, parameter range and core functions. The DDS-421 features a larger 7-inch color TFT touchscreen and includes three-level user management (Administrator / User / Visitor). The DDS-411 uses a smaller 4.3-inch color TFT touchscreen and does not include user management. Choose the DDS-421 for regulated multi-operator environments or when the larger display is beneficial; choose the DDS-411 for single-user or space-constrained applications.
The DDS-421 measures five parameters: conductivity, resistivity, TDS (total dissolved solids), salinity and temperature. These can be displayed simultaneously or individually. Automatic frequency and range switching ensures the instrument selects the optimal measurement conditions across the full range from 0.05 μS/cm to 500.0 mS/cm without manual intervention.
The DDS-421 is supplied with the DJS-1N (black) electrode, which covers 2–20000 μS/cm and is suitable for most standard water quality and laboratory applications. For ultrapure water measurement (below 2 μS/cm), use the optional DJS-0.1 (0.05–200 μS/cm). For high-conductivity solutions above 20000 μS/cm, use the optional DJS-10 (2000–200000 μS/cm). Contact us for application-specific electrode recommendations.
The DDS-421 supports two calibration methods: 1 to 3 point standard solution calibration using the four built-in standard solutions (146.5 μS/cm, 1408.3 μS/cm, 12.852 mS/cm and 111.31 mS/cm), and electrode constant calibration for use with non-standard or application-specific electrodes. For most laboratory applications, single-point calibration with the nearest standard solution is sufficient.
TDS (total dissolved solids) is calculated from the measured conductivity value using a user-configurable TDS conversion coefficient. The DDS-421 allows the TDS conversion factor to be set according to your specific sample type, providing accurate TDS readings in mg/L up to 100 g/L. This is particularly useful for water quality monitoring and industrial process water testing where TDS limits are specified.
The DDS-421 has USB and RS232 ports. Connect via USB with appropriate software to export measurement data in CSV format for import into LIMS, Excel or other data management systems. RS232 is available for connection to serial printers for GLP-compliant hard-copy records. All stored records include date, time and operator ID for full traceability.
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