The Personnel Sensor is a Passive Infra-Red (PIR) occupancy detector which detects the
presence / absence of the fume hood user.
Note: If the user is detected, the sash will not automatically close. The Sash can be opened /
closed manually or using the Up / Down pushbuttons.
On power up, the Personnel Sensor ‘learns’ the reflection characteristics of the environment
within its field of view and stores this information as reference background data. The sensor
then 're-learns' the background every three minutes. A stationary object, such as a stool, that is
left in the field becomes part of the background and is 'ignored' by the sensor. When the user is
not present at the fume hood, the sash will close automatically. This follows a pre-set delay
time, if the Sash Light Curtain is not broken and the sash is open.
4.3.3 Sash light curtain
The Sash Light Curtain is a safety device designed to detect whether the opening below the sash
is clear of obstructions before the sash is automatically closed.
• When an obstruction is detected, the sash drive is disabled and the alarm is activated.
• The Sash Light Curtain comprises an infra-red transmitter mounted on one side of the fume
hood and an infra-red receiver mounted on the opposite side of the fume hood's inner
chamber.
• The infra-red transmitter has multiple, closely spaced, Light Emitting Diodes (LEDs) to
facilitate the detection of small objects.
• Objects are detected when infra-red light from the transmitter is not detected by the
receiver due to an obstruction in its path.
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