Direct Answer: A drinking water conductivity sensor measures the electrical current carried by dissolved ions to estimate total dissolved solids (TDS). For regulatory compliance and stable long-term readings, select a CE-certified electrode-type sensor with automatic temperature compensation and a measurement range of 0–2000 μS/cm. The ERUN-A4D from ERUN Environmental meets these criteria with ±1% FS accuracy, IP68 protection, and ISO 9001 manufacturing controls.
Direct Answer: Conductivity sensors measure the water’s ability to conduct electricity, which is directly proportional to the concentration of ionized substances such as calcium, magnesium, sodium, chloride, and sulfate. In drinking water, this reading serves as a fast proxy for TDS and mineral content.
Electrical conductivity (EC) is the reciprocal of electrical resistance. When dissolved ions migrate under an electric field, they carry current. The more ions present, the higher the conductivity reading. For drinking water applications, European regulations generally require EC to remain below 2,500 μS/cm at 25°C to avoid unpleasant taste and scaling issues.
Because ion mobility changes with temperature—roughly 2% per 1°C—a reliable sensor must incorporate automatic temperature compensation. Without compensation, a summer reading of 800 μS/cm could falsely appear as 950 μS/cm or higher. The ERUN-A4D online conductivity analyzer includes built-in NTC10K or Pt100 temperature compensation, ensuring the reported value reflects the true ionic load rather than ambient water temperature fluctuations.
Direct Answer: High TDS indicates elevated dissolved minerals and salts, which can affect taste, pipeline corrosion rates, and treatment membrane performance. Monitoring conductivity provides a continuous, reagent-free early warning for treatment process upsets.
While TDS itself is not a primary health hazard at typical drinking water levels, it is a critical operational parameter. WHO guidelines and regional regulations set aesthetic and operational thresholds. Research on water sources shows that TDS and EC levels fluctuate seasonally: winter TDS often ranges from 338–616 mg/L, while summer values can reach 190–743 mg/L due to temperature-driven dissolution and agricultural runoff.
For treatment plant operators, sudden conductivity spikes can signal:
Membrane breach in reverse osmosis systems
Ineffective softening or demineralization
Contamination intrusion in distribution networks
Excessive mineral scaling risk in boiler feed or cooling systems
A CE-certified conductivity sensor with fast response time allows operators to divert or adjust treatment before non-compliant water reaches consumers.
Direct Answer: For European and international markets, a conductivity sensor should carry CE marking (covering EMC and electrical safety directives), RoHS compliance for restricted hazardous substances, and ISO 9001 certification for manufacturing quality consistency.
CE marking is mandatory for electrical and electronic products sold within the European Economic Area. It demonstrates conformity with applicable directives, typically the EMC Directive 2014/30/EU and Low Voltage Directive 2014/35/EU for water monitoring instruments. The technical documentation file must include risk assessments, test reports, and a signed Declaration of Conformity.
RoHS testing verifies that restricted substances—lead, mercury, cadmium, and certain phthalates—remain below threshold limits in soldered joints, cable insulation, and housing materials. This is particularly relevant for sensors that contact drinking water, as material leaching could compromise water safety.
ISO 9001 certification signals that the manufacturer operates a documented quality management system covering design, production, testing, and traceability. For procurement teams, these three credentials reduce audit burden and simplify import clearance.
ERUN Environmental manufactures the ERUN-A4D conductivity sensor under ISO 9001 quality controls, with CE and RoHS documentation available for international distributors and utility tenders. Product specifications and certificates can be requested via the ERUN product page.
Direct Answer: For drinking water, select a sensor with a cell constant K=1.0 and a range of 0–2000 μS/cm, installed in a flow-through or immersion configuration with IP68 protection. This covers typical municipal water (100–800 μS/cm) while allowing headroom for mineral variation.
The ERUN-A4D specifications align with these requirements:
| Parameter | Specification |
Measuring Range | 0–2000 μS/cm (K=1.0) |
Accuracy | ±1% FS |
Resolution | 1 μS/cm |
Temperature Compensation | NTC10K (optional Pt100/Pt1000), 0–60°C |
Pressure Range | 0–4 bar |
Housing Material | Stainless Steel |
Process Connection | G3/4 |
Protection | IP68 |
Output | 4–20 mA / RS485 (optional) |
For distribution network monitoring, immersion installation at storage tanks or booster stations works well. For treatment plant process control, flow-through housings maintain consistent sample contact. The G3/4 process connection is widely compatible with standard pipe tees and insertion fittings used in European and North American water utilities.
Q: Can I use a conductivity sensor to estimate TDS without a separate TDS meter?A: Yes. The standard approximation is TDS (mg/L) = EC (μS/cm) × 0.67. However, the exact conversion factor varies with ion composition—sodium chloride-dominated water has a different factor than calcium sulfate-dominated water. For regulatory reporting, use the sensor’s EC value directly or calibrate against a laboratory TDS measurement.
Q: Does the ERUN-A4D work with third-party transmitters or PLC systems?A: The sensor outputs a standard 4–20 mA analog signal and optional RS485 Modbus, making it compatible with most PLC, SCADA, and DCS platforms used in water treatment plants.
Q: What maintenance does an electrode conductivity sensor require in drinking water?A: Electrode-type sensors in clean drinking water typically require calibration verification every 3–6 months. Fouling is minimal in treated water, but periodic cleaning with dilute acid (for scale) or mild detergent (for biofilm) maintains accuracy. The stainless steel housing resists corrosion in chlorinated and low-mineral water.
ERUN Environmental — ISO 9001, CE, and RoHS certified manufacturer of online conductivity sensors and water quality analyzers for global drinking water and industrial treatment applications.
