Dwyer DPM - Manual (Page 11)

Particulate Monitoring Systems
Installation & Operating Manual
Document No. 210-1003-M Page 4 ©2007
2. Introduction
A Particulate Monitoring System consists of a control unit, a particulate sensor and a sensor coaxial
cable. Applications include continuous emissions monitoring, baghouse filter leak detection and
process particulate flow monitoring. Types of particulate include both solid particulates (dusts,
powders, granulars and pellets) and liquid particulates (mists). Various control unit models and
sensors are provided to match the application and process monitoring needs.
Principle of Operation
Particulate Monitoring Systems employ a highly reliable technology based on induction. A sensor
probe is mounted in an airflow stream such as a pipe, duct or stack (for small tubing an inline non-
intrusive ring sensor is employed). As particulate flows near and over the sensing element, minute
electrical currents are induced in the sensor and transferred to the control unit by a coaxial cable. A
microprocessor filters and processes the signal into a normalized, absolute output that is linear to the
mass concentration of particulate.
_ MASS CORRELATION
It is important to note that the above relation between instrument units (pA) and
actual mass (mg/m
3 or gr/cf) is just an approximate guide for selecting the
appropriate model and range and for providing a general indication of the typical
particulate levels monitored. For a true correlation between (pA) and actual
mass (mg/m
3 or gr/cf), a gravimetric correlation such as an isokinetic sample
must be performed for each application and a recommended model and
detection level must be ordered. It is also important to note that the accuracy of
such correlations is application dependent and produces the best results with
consistent particulate and process conditions. The user must follow proper
procedures and must understand the typical accuracy of such correlation
techniques. Consult factory for details.
Control Unit
The control unit (i.e. electronics) is housed in a rugged cast aluminum enclosure. An LCD displays
particulate levels in bar-graph and digital forms. A lockable membrane keypad is provided for setup
and adjustment. An optional self check sub system is available to automatically verify calibration and
operation of the control unit, sensor and cable. Various relay, analog inputs and outputs, as well as
serial communications are available in the control unit.
Particulate Sensor
The particulate sensor is very rugged and virtually maintenance-free. The sensor is passive with no
active circuits for high reliability and durability. It does not require special alignment and is not
affected by normal vibration.
Coaxial Cable for Particulate Sensor
The cable that connects the particulate sensor to the control unit is a high-quality coaxial cable
specifically designed for the system. Maximum length is 300 ft (91m). Do not use substitute cable.
IMPORTANT