| Measuring range | 0 – 40 NTU |
|---|---|
| Accuracy | ±2 % FS |
| Repeatability | ±1 % FS |
| Output signal | 4 – 20 mA / HART |
| Supply voltage | 12 – 36 V DC |
| Process connection | Ø 38 DIN 11851 |
| Enclosure protection | IP66 / IP67 IEC 60529 |
| Operating temperature | 5 – 45 °C |
Can one turbidity reading replace a laboratory sample?
No. The online value follows the trend of what passes the window every second, while a laboratory method reports a defined property of one grabbed sample; the two answer different questions and are best used together to watch each other for drift.
Why does a turbidity sensor care about CIP compatibility?
Because process fouling on the optical window mimics a real solids signal, a sensor that can be washed inside the existing clean-in-place circuit removes the most common cause of false alarms without breaking containment.
What does a 4-20 mA output bring to system integration?
A two-wire current loop that is hard to mis-wire, tolerates long cable runs, carries the same current at both ends, and lets a broken wire show up as an end-of-scale fault instead of a plausible-looking number.
Definition
An online turbidity sensor estimates the load of suspended particles in a flowing liquid from the light they scatter, reporting a continuous reading of clarity.
The ATU-200 addresses the need for one continuous turbidity reading that spans clear filtered water and the heavier loads seen during backwash, so filter breakthrough shows up without laboratory sample grabs.
How scattered-light turbidity measurement works
The transmitter shines a beam into the water and reads part of the light deflected by suspended particles at an angle to the incoming beam. The stronger the scattering signal relative to a clean reference, the higher the solids load the optical path is seeing. Because the reading is optical, it responds continuously to whatever passes the window, which is what a treatment operator needs between manual grab samples. A laboratory method and an online instrument answer different questions, and both are usually kept on purpose.
Keeping the window clean in CIP service
Fouling of the optical window is the main error source in online turbidity work, because a film of biofilm or precipitate scatters light much the same way real solids do. The ATU-200 keeps the wetted path short and drainable so it can be washed together with the process line, and its sensor body is meant to sit in the same clean-in-place circuit as the equipment it watches. Cleaning frequency then follows the trend of the baseline reading rather than a fixed calendar, and every wash is documented the same way the rest of the circuit is.
Wiring and signal checks on site
The unit carries the standard two-wire loop signal, so commissioning comes down to confirming loop supply, wire length and the load the receiver expects. When a reading looks wrong, the fastest field check is to compare the live loop current against the value the display reports, then inspect the window and the flow before touching any setting. Recording the current drawn at a known clean-water state gives the next technician a baseline that does not depend on memory. A note of the water source and the last wash date belongs in the same record, so future crews compare like with like.
All figures on this page are illustrative sample values, not measured specifications.