Viomax CAS51D

Summary

Product Identification

• Product Name: Viomax CAS51D
• Type: Photometric sensor for measuring the spectral absorption coefficient (SAC) or nitrate content.
• Document: TI00459C/07/EN/17.24-00

Application

The Viomax CAS51D is designed for:

• SAC Measurement:
  • Organic load in WWTP inlet and outlet.
  • Discharger monitoring.
  • Organic load in drinking water.
• Nitrate Measurement:
  • Nitrate content in natural bodies of water.
  • Nitrate content in WWTP outlets and aeration basins.
  • Monitoring and optimizing denitrification phases.

Benefits

• Affordable and environmentally friendly.
• Chemical-free measurement.
• Low-maintenance with long intervals due to compressed air cleaning.
• Data conditioning within the sensor.
• Minimal sensitivity to interference during signal transmission.
• Short response time for early detection of load peaks.
• Factory calibration for immediate use.
• Standardized communication with Memosens technology for "plug and play".
• Customer calibrations with 1-5 points are possible.

Function and System Design

Measuring Principle

The sensor uses a pulsed strobe lamp. Light passes through a measurement gap and is split to two receivers. Filters allow only specific wavelengths to pass to each receiver. The ratio of light signals at the measuring and reference wavelengths is calculated to minimize effects of turbidity and lamp aging. This ratio is converted to nitrate concentration or SAC value.

• Nitrate Measurement: Measures UV light absorption at 214 nm (measuring) and 254 nm (reference). Nitrate and nitrite ions absorb light at 214 nm.
• SAC Measurement: Compares absorption at 254 nm (measuring) with 550 nm (reference). KHP (potassium hydrogen phthalate) is used as the organic reference.

Measurement Gaps

• Nitrate Measurement:
  • 8 mm (0.31 in) measurement gap for clear water.
  • 2 mm (0.08 in) measurement gap for media with high turbidity (e.g., activated sludge).
• SAC Measurement:
  • 40 mm (1.57 in) measurement gap for clear water samples with low SAC values.
  • 2 mm (0.08 in) measurement gap for measuring organic load in WWTP inlets with high turbidity.

Cross-Interference

• Nitrate Measurement: Affected by total solids (TS), turbidity, sludge properties, and nitrite. Nitrite is measured as nitrate, with 1 mg/l nitrite displayed as 0.8 mg/l nitrate.
• SAC Measurement: Affected by turbidity and color. Oxidizable substances absorbing at 550 nm or substances with different absorption behavior than KHP can affect results.

Measuring System

A complete system includes:

• Viomax CAS51D sensor
• Liquiline CM44x multi-channel transmitter
• Universal installation or flow assembly (e.g., Flexdip CYA112, Flexdip CYH112, Flowfit CYA251, CAV01).

Input

Measured Variables

• Nitrate: NO₃-N [mg/l], NO₃ [mg/l]
• SAC: SAC [1/m], COD [mg/l], TOC [mg/l], BOD [mg/l], DOC [mg/l], transmission [%]

Measuring Range

• Empirical COD values:
  • Municipal WWTP Inlet: 0 to 4000 mg/l COD
  • Milk-processing industry Influent: 0 to 10,000 mg/l COD
  • Chemical industry Influent: 0 to 10,000 mg/l COD

Electrical

• Power Supply: Via M12 plug or sensor cable to transmitter.
• Maximum Cable Length: 100 m (328.1 ft).

Performance Characteristics

• Reference Operating Conditions: 20 °C (68 °F), 1013 hPa (15 psi).
• Measurement Error:
  • Nitrate (2 mm gap): 2% of full scale (>10 mg/l NO₃-N), 0.4% of full scale (<10 mg/l NO₃-N).
  • Nitrate (8 mm gap): 2% of full scale (>2 mg/l NO₃-N), 0.2% of full scale (<2 mg/l NO₃-N).
  • SAC: 2% of full scale (with KHP).
• Repeatability:
  • Nitrate: ±0.2 mg/l NO₃-N minimum.
  • SAC: 0.5% of end of measuring range (homogeneous media).

Detection Limits

• Nitrate:
  • CAS51D-AAA1: 0.003 mg/l NO₃-N
  • CAS51D-AAA2: 0.013 mg/l NO₃-N
• SAC (relative to KHP):
  • CAS51D-AAC1: 0.045 mg/l COD
  • CAS51D-AAC2: 0.3 mg/l COD
  • CAS51D-AAC3: 1.5 mg/l COD

Determination Limits

• Nitrate:
  • CAS51D-AAA1: 0.01 mg/l NO₃-N
  • CAS51D-AAA2: 0.043 mg/l NO₃-N
• SAC (relative to KHP):
  • CAS51D-AAC1: 0.15 mg/l COD
  • CAS51D-AAC2: 1.0 mg/l COD
  • CAS51D-AAC3: 5.0 mg/l COD

Long-term Drift

• Nitrate: Better than 0.1 mg/l NO₃-N over one week.
• SAC: Better than 0.2% of end of measuring range over one week.

Installation

Mounting Location Considerations

• Avoid locations with air pockets or foam.
• Ensure easy accessibility.
• Secure and vibration-free mounting.
• Align the sensor so the measurement gap is rinsed by the medium flow.
• Do not install above aeration discs to prevent bubble accumulation.
• Select a location representing typical application values.

Orientation

Align the sensor with the medium flow to ensure rinsing and air bubble removal.

Assemblies

• Flexdip CYA112 / Flexdip CYH112: Immersion assembly for open basins, channels, and tanks. Can be installed horizontally or vertically.
• Flowfit CYA251: Flow assembly for horizontal installation.
• CAV01: Flow assembly for horizontal installation.

Environment

• Ambient Temperature Range: –20 to 60 °C (–4 to 140 °F).
• Storage Temperature: –20 to 70 °C (–4 to 158 °F).
• Degree of Protection: IP 68 (1 m (3.3 ft) water column, 24 hours, 1 mol/l KCl).
• Process Temperature Range: 5 to 50 °C (41 to 122 °F).
• Process Pressure Range: 0.5 to 10 bar (7.3 to 145 psi) absolute.
• Minimum Flow: No minimum flow required, but ensure sufficient mixing for solids prone to deposits.

Mechanical Construction

Dimensions

Dimensions vary based on the measurement gap size (2 mm, 8 mm, or 40 mm). See the document for specific diagrams and measurements.

Cleaning Unit

Dimensions provided for the adapter with hose and connections.

Weight

• Approx. 1.6 kg (3.53 lbs) (without cable).

Materials

• Sensor Body: Stainless steel 1.4404 (AISI 316 L).
• Optical Windows: Quartz glass.
• O-rings: EPDM.
• Process Connections: G1, NPT ¾", Clamp 2" (depending on version).

Certificates and Approvals

Information on current certificates and approvals can be found on the Endress+Hauser website. The EAC mark indicates conformity with TP TC 004/2011 and TP TC 020/2011 for the European Economic Area.

Ordering Information

Product configuration is done via the product configurator on www.endress.com/cas51d.

Scope of Delivery

• Sensor in the ordered version.
• Operating Instructions.

Accessories

• Assemblies: Flexdip CYA112, Flowfit CYA251, CAV01.
• Holder: Flexdip CYH112.
• Cleaning: Cleaning brushes, compressed air cleaning units (requiring pressure of 1.5 to 2 bar), and compressors.
• Standard Solutions: Nitrate standard solutions and KHP standard solution are available.

Disclaimer: This extraction may miss figures, footnotes, or revisions. Contractual data must match the OEM PDF revision used on the project.

Official datasheet (PDF)

Lenntech datasheet mirror