McNab Model HSD Back Scatter Yeast Analyzer
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automatic and continuous real-time unattended monitoring of suspended
solids concentration in liquid process vessels
Technical Papers/News Releases:
How It Works
The HSD probe assembly contains a combination detector unit, a sensor assembly and McNab's exclusive modular optical cell. The probe assembly mounts directly in the wall of the tank being monitored and the process liquid passes in front of it. The parameter is measured by passing a light beam into the process liquid and measuring the light scattered back to the probe. The light back-scattered (or fluorescence) to the detector is proportional to the signal of interest in the liquid. The signals are then sent to the indicator/controller cabinet.
The indicator/controller cabinet contains the modular electronic circuitry necessary to process the signals, to display the readings, to input desired set-points, to indicate alarm levels and to operate alarm relays. It also has continuous output for proportional control connections.
Because the probe assembly is vessel-mounted, without the need for the measuring beam to go across the process fluid, two heads are not necessary
The HSD provides immediate measurements at operational pressures and temperatures. Errors potentially caused by sample temperature and/or pressure variations are avoided, as are compromises normally required of off-line sample lines.
The optical window can be visually inspected anytime without vessel drainage. McNab's unique modular optical cell can be quickly hand-removed for off-line inspection, pressure test or replacement of the unit and/or to inspect the wetted surface. This design has effectively eliminated the measuring problems often caused by glass fogging, condensation, power and/or temperature fluctuations, or light-source bulb aging.
The Model HSD uses the very latest optical technologies to provide stable, low-noise signals across the range of light used for measuring.
Model HSD photometric analyzers measure process liquids in tanks with:
No Standardization Required
The HSD achieves measurement stability of 0.5% per year, allowing maintenance-free operation. This is made possible by a matched signal verifying module (SVM), with 100-megohm input impedance. This eliminates drift, so there is no need for constant restandardization. The SVM also corrects for any variation in sensor cable length, so nearby electric interference does not affect operation, even at cable distances of 600 feet (180m).
Advanced Optical and Electronic Design Provide Greater Range
The HSD’s electronics have been specially designed so that the digital meter readings can be adjusted to fit parts-per-million (ppm) units.
The HSD/B operates on the reflection principle. The formula is:
or in the HSD/A diffuse reflection, and this formula would be:
Continuous Accuracy Verification
The HSD features McNab's exclusive lens fog alarm transmitter. This unique feature verifies accuracy of the analyzer by continuously monitoring the modular optical cell against the fogging effects of moisture.
An alarm system is contained within the indicator/controller cabinet to advise plant personnel when measuring accuracy is in danger of being compromised.
When the moisture removal system has reached the end of its useful life, or has been otherwise disturbed, an alarm will be indicated on the remote panels and may be coupled in to the 4-20 mA loop to signal the console of lens fogging.
This feature assures accuracy of the readings and helps reduce preventive maintenance requirements.
Comparing other photometric instruments to McNab
McNab Photometric Analyzers
Other McNab instrumentation is available to provide photometric analysis of such items as particle size and/or concentration – using monitors that measure using nephelometric (scatter) and forward-scatter technologies for the measurement of low-level particles (NTU, PPM, EPA, etc.) – as well as high-level chemical concentration, optical density and others.
McNab, Inc. is located in metropolitan New York City. Our offices in Mount Vernon, New York include our research & development laboratory, design engineering department, modern manufacturing plant and automatic testing facilites to evaluate our products. McNab's Quality Assurance Process meets Mil-I-45208. We also maintain an engineering and parts facility in Europe.