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Teledyne API Ultrafine Particle Monitor - Model 651 Technical Description
07506C DCN6727 57
The critical pressure ratio is found by dividing the absolute
pressure downstream of the orifice P
D
, by the absolute pressure
upstream of the orifice P
U
. This ratio must be below 0.528 for air.
528.0pressure Critical
U
D
P
P
The following pressure values are displayed on the Status screen
and can affect the Model 651 flow.
Pressure Value Description
Vacuum
The vacuum pressure
Inlet Pressure
The inlet pressure.
Nozzle Pressure
The differential pressure across the sensor flow
orifice
Temperature Control
The temperatures of the conditioner, growth tube, and optics are
nominally maintained at 20°C, 60°C, and 60°C, respectively, with
specified ambient temperatures in the operating range of 10°C to
40°C. Temperatures are controlled through feedback circuits on the
main electronics board and are displayed on the Status screen on
the front-panel display.
Note: For ambient temperatures outside the instrument operating
range, the instrument temperature performance may not be
maintained. Moderate increases in conditioner temperature
will raise D
50
a small amount.
Vacuum Supply
The external vacuum supply must be sufficient to maintain the
sample flow at 0.12 L/min along with the auxiliary and transports
flows. The recommended supply is 4 SLPM at 400 mbar absolute
pressure.
Inlet Pressure Measurement
With an adequate vacuum supply, the Model 651 can operate at
inlet pressures in the range of 75 to 105 kPa. The inlet pressure is
measured by an absolute pressure sensor and is equal to the
barometric pressure if no inlet restriction is present.