Dwyer PMT - Manual (Page 12)

Particulate Monitoring Systems
Installation & Operating Manual
Document No. 210-1015-F Page 6 ©2007
3.3 Particulate Sensor/Probe
The particulate sensor consists of a stainless probe with a non-conductive protective layer or coating,
a stainless steel nipple/mount and the sensor housing. It is a very rugged assembly that is virtually
maintenance-free. It does not require special alignment, is not affected by normal vibration and does
not require cleaning.
3.4 Smart Transmitter Module
The smart transmitter module processes the signals induced into the probe, quantifying and digitally
filtering them into an absolute measurement of pA (picoamps). The pA reading is transmitted over a
4-20mA current loop for remote monitoring with a control system, PLC, panel meter, recorder etc. It
is important that the 4-20mA signal be converted back into pA at the monitoring location to enable
evaluating the instrument output readings properly. Electrical isolation is provided between the 4-
20mA loop and the pA measurement circuitry. This isolation provides immunity to ground loop and
power supply/plc analog input card grounding possibilities.
The smart transmitter module is located directly inside the particulate sensor housing for one-piece
configurations. For two-piece configurations the smart transmitter module is located in a separate
TYPE 4X enclosure.
3.5 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.
This cable is required for two-piece configurations only.
3.6 Sensor Test Port (Non-Hazardous Areas Only)
The test port is not a necessary component to operate the system, but it is recommended. It is a
1/8”NPT x 3” pipe nipple used to introduce particulate into the process to perform a natural response
check. The nipple is screwed into or welded to the pipe/duct upstream of the sensor. Particles are
injected into the flow stream to simulate a natural increase in particle flow. It is primarily intended for
use at negative pressure locations in fabric filter outlet ducting so that when the cap is removed line
suction will enable particles to be sucked into the flow. A test port is not recommended for hazardous
area applications.
Location: A test port should be installed in a negative pressure location. It must be located upstream
of the sensor so particulate can flow very near and around the sensor. It should be located at least 3 ft
(1 m) upstream of the sensor and it should be located on the same side of the duct as the sensor so
particles can pass very near and around the sensor. If possible locate the test port at ground level.
Mounting: The test port is either screwed into a 1/8 inch NPT threaded hole, or welded in position.
(Note: A foot or so of tubing can be connected to the nipple to make it easy to draw particles out of a
container. Only a pinch of particulate at a time is needed for a response check.)
_ TEST PORT INSTALLATION
• Installation of a sensor test port enables checking the response to an actual
increase in particulate.
IMPORTANT