McNab Model HSB High Sensitivity Clarity Analyzer

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Model HSB-XP (Explosion Proof)

• High sensitivity
• 90-degree scatter
• Four-head design

A nephelometric particle measuring instrument, self-correcting for variations in illumination, color & fouling of optical surfaces.

Related Technical Papers/News Releases:

• Brewery uses turbidimeter to constantly monitor beer clarity

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• Optical Measurement of In-Process Fluids

• Payout Economics on Process Stream Analyzers

• Turbidity monitoring system aids in the removal of solids as small as 0.5 microns

• Turbidity monitoring system continuously checks filter performance in fruit juice production

How It Works

Scatter is the effect particles have on a light shining through liquid. Typical engineering units are PPM (parts per million), NTU, EBC, JTU and others.

In a scatter analyzer, light is collimated in a liquid, and the light scattered (by reflection, etc.) is proportional to the concentration of particles.

The HSB measures light scatter at a right angle to the incident light. This has become an international standard, accepted by the EPA in the United States, the EBC in Europe and other authorities

The Model HSB consists of a flow cell unit and the control/indicator unit.

The unique 4-chamber design isolates scatter, transmitted and trapped stray light.

The flow cell includes:

1. The optical light source.

2. The measuring detector which measures light scattered 90 degrees from the main light path – the nephelometric measurement.

3. The reference detector measures transmitted light from the main light source to provide a compensating ratio for variations in color, lamp deterioration and/or fouling of optical surfaces.

4. A test lamp is used to test the measuring detector sensor. This also provides a light trap.

The indicator/control cabinet contains the modular electronic circuitry necessary to process signals from the photo-sensors to provide readings in the required units, to display those readings, to input desired set points, to indicate alarm levels, to operate relays and to provide self-diagnostics.

From Light Beer to Coal Slurry…

McNab Clarity Analyzers measure suspended solids in process liquids with:

• 0.1% Repeatability per year
• Complete international conformance—EPA, DIN, ISO; correlates with original hazemeter and other instruments

No Standardization Required

The HSB achieves measurement stability of 0.1% per year, allowing maintenance-free operation. This is made possible by two critical matched signal verifying modules (SVMs), each with 100-megohm input impedance. These SVM’s eliminate drift, so there is no need for constant restandardization. SVM's also correct for any variation in sensor cable length, so nearby electric interference does not affect operation, even at cable distances of 600 feet (180m).

Built-in Zero Standard

The unique built-in zero standard can be used at any time to verify standardization, even when the process is operating. Simply press the test button, and the system verifies that actual standardization has been maintained; no drift has occurred. No down time or removal is needed.

High-Sensitivity Measurement In Problem Liquids

New high technology optics and UV-enhanced sensors deliver 1,000 times more sensitivity than was possible just a few years ago. The HSB uses this dramatic improvement to measure suspended solids in "problem" liquids like dark stout and orange juice.

Complete Color Compensation

Color is "dissolved" in a liquid. Color does not scatter light, but it will attenuate light, interfering with accurate particle measurement.

To prevent color interference, the Model HSB measures light attenuated by color and completely adjusts for this interference. The result is accurate, stable measurements without moving parts or adjustments.

Center-Of-Pipe Measurement

The ideal scatter measurement is made in the center of the actual process pipe. Near the pipe wall, in a by-pass pipe or in a slipstream, scatter particles will settle out because minimum velocity is not maintained. To eliminate this problem, the HSB measures only in the high velocity region in the center of the pipe. This is essential for high accuracy measurement and can yield a 2:1 improvement in accuracy.

Extended-Life Light Source

Optical lamp life has been extended to an average of five years by use of optional improved lamp control circuitry. This makes a truly maintenance-free system.

High Sensitivity For Ultra-Clean Liquids

Measurement of liquids, like WFI and ultra-pure water, requires high sensitivity measuring geometry. The HSB uses a new, proprietary light trap chamber to give a 3:1 improvement in sensitivity over the previous state of the art. This chamber configuration traps stray light that would otherwise block high-sensitivity measurement, as in other designs.

About McNab

Specifications

A90-85B  Rev B