SLURRY WATER CIRCUIT | GENERAL INSTRUMENTATION
Turbidity / Sludge Concentration Meter
One probe, two measurements: turbidity and sludge concentration, both scalable to the same isolated 4-20 mA output. Built for thickener overflow monitoring, where clarity is the number that tells you whether the water is actually fit to recycle or discharge.
0 – 4,000 NTU
Turbidity Range
0.1 – up to 120,000 mg/L
Sludge Concentration (model-dependent)
±2% of reading or ±0.1 NTU
whichever is greater, Turbidity Accuracy
IP68 / NEMA 6P
Probe Rating
DEFINITION & OVERVIEW
What is a turbidity / sludge concentration meter?
A turbidity meter measures water clarity and how much suspended solid material is scattering light through the sample, which is exactly the number that confirms whether thickener overflow water is clean enough to recycle or discharge. The same probe on this instrument also measures sludge concentration, giving two related process variables from one installation point.
Both measurements scale to the same isolated 4-20 mA output, so the control system reads whichever variable the installation point actually needs without requiring two separate instruments. Two independent NO/NC contacts plus RS485 Modbus-RTU communication cover both simple alarm duty and full SCADA integration from the same unit.
The probe is rated IP68/NEMA 6P for continuous submersion, with the indicator rated IP54 and a 10 m standard cable extendable to 100 m built for installation directly in the process stream rather than a bypass sample line.
Two Measurements, One Probe
Turbidity and sludge concentration are both measured from the same submersible probe, scalable to a single 4-20 mA output.
Built for Submersion
IP68/NEMA 6P probe rating supports direct installation in the process stream, not just a bypass sample line.
Flexible Output
Isolated 4-20 mA, two NO/NC contacts, and RS485 Modbus-RTU cover both simple alarming and full SCADA integration.
Parameter | Value |
|---|---|
Turbidity Range | 0.00 – 4,000 NTU |
Sludge Concentration Range | 0.1 – 20,000 / 45,000 / 120,000 mg/L (model-dependent) |
Turbidity Accuracy | ±2% of reading or ±0.1 NTU, whichever is greater |
Sludge Concentration Accuracy | ±5% of reading |
Output | Isolated 4–20 mA, scalable to either variable |
Contacts / Communication | Two independent NO/NC contacts; RS485 Modbus-RTU |
Indicator / Probe Rating | Indicator IP54 with 2.8 in LCD; probe IP68 / NEMA 6P |
Probe Cable | 10 m standard, extendable to 100 m |
KEY FEATURES
Key Features & Performance Highlights
Built specifically for continuous thickener overflow monitoring, where a single probe covering two related variables reduces installation points without losing measurement independence.
Dual-Parameter Measurement
Turbidity and sludge concentration are measured independently from the same probe, each scalable to the isolated 4-20 mA output; the control system reads whichever variable matters at that point in the circuit.
Whichever Is Greater Accuracy Spec
Turbidity accuracy is stated as ±2% of reading or ±0.1 NTU, whichever is greater, meaning the instrument maintains absolute accuracy at low NTU readings rather than degrading proportionally, which is most important where overflow clarity is being verified as genuinely clean.
Submersible Probe, Extendable Cable
An IP68/NEMA 6P probe rating with a 10 m standard cable extendable to 100 m supports installation directly in the process stream at a distance from the indicator, without a separate junction box.
WORKING PRINCIPLE
How the Turbidity / Sludge Concentration Meter Works
One submersible probe feeds two process variables to the same output architecture. The exact sensing arrangement below is stated at a general level; pending confirmation of the specific optical method for each variable, see the note in Key Features.
Probe Submersion
The IP68/NEMA 6P probe is installed directly in the thickener overflow stream or sample point.
Optical Measurement
The probe measures turbidity and sludge concentration, each read from the sensing element appropriate to that variable.
Signal Scaling
The isolated 4-20 mA output is scaled to whichever variable turbidity or sludge concentration the installation point requires.
Alarm and Communication
Two independent NO/NC contacts provide local alarming, while RS485 Modbus-RTU communication feeds the same data to the plant SCADA.
Local Display
The IP54-rated indicator with 2.8 in LCD displays the live reading at the instrument, independent of the remote signal.
TECHNICAL SPECIFICATIONS
Turbidity / Sludge Concentration Meter | Full Specification
Specifications sourced directly from John Finlay’s instrumentation documentation.
Parameter | Value |
|---|---|
Turbidity Range | 0.00 – 4,000 NTU |
Sludge Concentration Range | 0.1 – 20,000 / 45,000 / 120,000 mg/L (model-dependent) |
Turbidity Accuracy | ±2% of reading or ±0.1 NTU, whichever is greater |
Sludge Concentration Accuracy | ±5% of reading |
Output | Isolated 4–20 mA, scalable to either variable |
Contacts | Two independent NO/NC contacts |
Communication | RS485 Modbus-RTU |
Indicator Rating | IP54, 2.8 in LCD |
Probe Rating | IP68 / NEMA 6P |
Probe Cable | 10 m standard, extendable to 100 m |
COMPARISON
Continuous Turbidity Monitoring vs. Manual Sampling
With a Turbidity/Sludge Concentration Meter
Manual Sampling (Typical)
Applications of the Turbidity / Sludge Concentration Meter
This instrument is specified wherever thickener overflow or process water quality needs continuous verification rather than periodic sampling.
Thickener Overflow Monitoring
Confirms overflow water clarity continuously before it's recycled or discharged.
Recycled Water Quality Assurance
Continuous turbidity data supports water balance decisions on whether recycled water meets process requirements.
Sludge Concentration Tracking
The same probe tracks sludge concentration for circuits where that variable matters alongside clarity.
Discharge Compliance Monitoring
Continuous clarity verification supports discharge quality requirements without relying on periodic grab samples.
Thickener Performance Diagnostics
It is part of a complete thickener instrumentation offering that includes flow, interface level, and underflow density measurement.
SCADA-Integrated Water Circuits
RS485 Modbus-RTU and 4-20 mA outputs integrate directly into existing plant automation.
About John Finlay
Turbidity Instrumentation Supplier in India
Why John Finlay?
4,000
NTU Turbidity Range
Covers the full range from near-clean water to heavily loaded overflow, all from a single probe.
130+
Coal Washery Projects
Completed EPC projects worldwide, including Asia’s largest coking coal washery at 30 MTPA.
EPC
Full Circuit Supply
Supplied as part of a complete thickener instrumentation offering, alongside flow, level and density measurement.
IN
India-Based Support
Manufactured at Hefei John Finlay Mining Equipment Co., Ltd. and supported locally in India for installation, commissioning, spares and service.
Turbidity / Sludge Concentration Meter | Frequently Asked Questions
Common questions from engineers in coal washery processes evaluating continuous turbidity and sludge concentration measurement.
Yes, both are measured independently from the same submersible probe, each scalable to the isolated 4-20 mA output depending on which variable the installation point needs.
Turbidity covers 0.00–4,000 NTU. Sludge concentration covers 0.1 up to 20,000, 45,000, or 120,000 mg/L depending on the model.
Turbidity accuracy is ±2% of reading or ±0.1 NTU, whichever is greater. This is what makes the instrument hold absolute accuracy at low readings rather than degrading proportionally. Sludge concentration accuracy is proposed at ±5% of reading.
Yes, the probe is rated IP68/NEMA 6P for continuous submersion, with a 10 m standard cable extendable to 100 m, supporting installation away from the indicator without a separate junction box.
Yes, RS485 Modbus-RTU communication and isolated 4-20 mA output integrate directly into existing plant automation, along with two independent NO/NC contacts for local alarming.
Not sure if your overflow water is actually clean enough to recycle?
Our engineers can help you specify continuous turbidity monitoring for your thickener overflow.
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