Sampling System; Inlet; Aerosol Sample Conditioner (Asc); Optical Particle Sensor - Teledyne T640 User Manual

SAMPLING SYSTEM

There are several components that are part of drawing in and measuring aerosol
samples: the inlet, the Aerosol Sample Conditioner (ASC), an optical particle
sensor, a flow sensor, and pump.

INLET

The inlet for the T640 is designed to allow complete transmission of all particle
sizes.
The US EPA PM10 inlet used for the 640X Option samples at 16.67-LPM to
mechanically size-cut the aerosol intake for sampling particles at 10 microns and
under.

AEROSOL SAMPLE CONDITIONER (ASC)

The ASC removes volatile components (mainly water) of the aerosol to avoid false
particle size. Its operation includes an air sensor for measuring ambient temperature
and humidity in order to dynamically adjust the heating of the ASC tube for
moisture/humidity compensation.

OPTICAL PARTICLE SENSOR

The optical particle sensor is the main sensor in the instrument. This sensor
analyzes the particles, categorizing them by size and making the conversion to a
mass concentration.

FLOW SENSOR AND PUMP CONTROL

The T640 operates using ambient temperature and pressure compensated mass
flow, for accurate control of flow to actual volumetric conditions. The flow stream
is measured (main flow at 5 LPM for T640 and bypass at 11.67 for 640X Option),
and a feedback loop triggers the pump drive voltage adjustments to maintain a
constant flow (5 LPM in the T640, 16.67 LPM in the 640x Option).
The internal vacuum pump is a 24V DC pump controlled by a pulse-width
modulation (PWM) feedback control for consistently accurate flow through the
sensor.
The external vacuum pump (640X Option only) uses either a 110-120 or 220-
240VAC pump. The bypass flow is controlled at 11.67 LPM by a proportional-
integral-derivative (PID) feedback control for consistently accurate flow through
the PM
bypass flow at 11.67 LPM make up the necessary 16.67 LPM for the US EPA PM
inlet proper size cut.
08354B DCN7877
inlet. The combined flow of the internal pump at 5 LPM along with the
10
Teledyne API T640 PM Mass Monitor
10
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