What is the difference between TDS and electrical conductivity measurements?
Electrical conductivity (EC) measures the ability of water to conduct electricity, expressed in microsiemens per centimeter (uS/cm). TDS (Total Dissolved Solids) is calculated from conductivity by applying a conversion factor, typically 0.5-0.7 depending on the ion mix in the water. Conductivity is the direct measurement; TDS is a calculated estimate. For RO performance monitoring, conductivity is the more precise indicator of salt passage.
What measurement ranges do your TDS and conductivity monitors cover?
Our inline and portable monitors cover 0-9,999 ppm TDS and 0-19,999 microsiemens per centimeter conductivity. High-range models extend to 99,999 uS/cm for seawater and brine applications. For high-purity water applications such as semiconductor or pharmaceutical manufacturing, low-range units measure 0-10 uS/cm with resolution of 0.01 uS/cm. Selecting the correct range for your application is important for measurement accuracy.
How are TDS monitors used to verify RO system performance?
Operators monitor both feed water TDS and permeate TDS continuously to calculate percent rejection: rejection equals (1 minus permeate TDS divided by feed TDS) times 100. A new RO system with brackish water membranes should achieve 97-99% rejection. A drop of more than 1-2 percentage points from baseline indicates membrane fouling, scaling, or physical damage requiring investigation. Inline monitors with 4-20mA outputs enable SCADA-based automatic alarming.
Can TDS monitors detect problems with water softeners or DI systems?
Yes. A TDS monitor on the outlet of an ion exchange softener can detect hardness breakthrough before it reaches downstream equipment. For DI (deionization) systems, conductivity monitoring detects resin exhaustion. DI effluent should measure below 1 uS/cm (less than 0.5 ppm TDS) when resin is fresh. Rising conductivity at the DI outlet signals time to regenerate or replace the resin, protecting sensitive downstream equipment from hardness or ionic contamination.
Are your monitors suitable for continuous inline installation or only spot-checking?
We offer both configurations. Inline monitors with flow cells install directly in pipe runs (1/2-inch to 2-inch connections available) and provide continuous real-time readings with 4-20mA, RS-485, or relay outputs for PLC integration. Portable handheld units are calibrated instruments for field spot-checking, commissioning, and troubleshooting. Many facilities use inline monitors on critical streams and a portable unit for auxiliary checks throughout the plant.
How often do conductivity sensors need calibration?
Conductivity cells should be calibrated against a traceable standard solution every 3-6 months for process monitoring applications. Critical applications such as pharmaceutical water or semiconductor fab require monthly calibration verification. Cell constant drift occurs gradually due to fouling or electrode wear. Our inline sensors include tool-free removal for cleaning and recalibration without process shutdown. Calibration standard solutions (84 uS/cm and 1,413 uS/cm) are available separately.