Combined sample probe for simultaneous dust, flow,temperature and pressure measurements.

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Feb 2000 Analytical Instrumentation & Environmental Monitoring

OEN Enterprisers -

Durag's D-RX 250 is a new combined sample probe which is capable of measuring dust concentration, volume flow, absolute pressure and temperature simultaneously. It is designed for continuous monitoring of dust concentration in flue gas ducts, dust extraction pipes and similar applications.

The transmitter is mounted at the measuring point and with transmission of the raw data via the bus interface, the mounting location of the operating and evaluation unit can be positioned up to 100 m from the measuring point. Alternatively, the raw data can also be computed by an emission computer or a process control system.

Dust concentration is determined according to the tribo-electric measuring principle while the volume flow measurement operates on the differential pressure principle. The absolute pressure in the flue gas is sampled in one chamber of the probe and measured by a piezo-resistive pressure transmitter. Temperature is measured in a separate chamber within the probe directly in the core flow of the flue gas by a Pt100 resistance thermometer.

The probe is mounted in the stack path using a flange that is connected to the stack. The probe is built in isolation due to the tribo-electric measurement and contains two chambers for the measurement of differential and absolute pressure. The gas temperature is measured in a third chamber.

The differential pressure transducer detects the flow of speed of the gas and transmits this as a 20 mA measurement signal to the transmitter. The transmitter is connected to the probe and modifies the tribo-electric current, the temperature sensor's signal, absolute pressure, as well as the volumetric flow value from the differential pressure transducer to raw values and transmits these over a bus interface to the control and evaluation unit.

These raw values are received by the operating and evaluation unit, which computes the normalised dust concentration from them. Measurements are available as 20 mA current signals for dust concentration volume flow, temperature and absolute pressure together with a series of associated status signals.

Operation is menu-guided using four keys and a 4-line display. The measurements are displayed in various menus and for improved readability, measurements can be shown in large characters. The probe is not suitable for use after an electrostatic precipitator, in wet stack gases, or where abrasive dust particles may damage the probe.

OEN Enterprises

(011) 792 2859

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Analytical Instrumentation & Environmental Monitoring

Combined sample probe for simultaneous dust, flow,temperature and pressure measurements.

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