MiniBSV FAST(Indoor) Manual
MiniBSV FAST is a low price sensor for visibility in heavy fog like smoke orsnowstorm etc. The main application is detection of different kinds of very low
visibility in a fast reaction. To make it happen, FAST model outputs measured
visibility in every 1 second.

The sensor is heated to a few degrees above ambient temperature in order to keep
moisture away. In order to keep the electronics dry a membrane ventilator that keeps
the pressure inside at the same level as outside. This prevents liquid water fromsucking into the sensor through micro cracks etc. at falling temperature – a creative
solution to a big problem.
The sensor produces analog and digital signals:

About the analog output:
The microprocessor controls the analog output giving the visibility directly (vis=0100
meters gives 0.5 Volt, and up to 5 Volt at 1000 meters by 20mV steps). While temporalmeasurement errors such as sensor saturations by sunlight or reflections from anobject it the sensitive zone like an insect of fallen snow covering the front, the sensor
outputs 5 Volt as an error code. The analog output is refreshed at each every 1 second
after once the voltage is dropped to 0 volt.

About the digital output:We recommend this digital output since more and better information can be taken fromit. The calculated data is presented in digital form as an ASCII string on theRS232output, 19,200 baud 8N1, that is transmitted “streaming” every 1 second the fixed
length data. This string can be received by many loggers with RS232 inputs but also by
a PC via the serial port and with a terminal program like TeraTerm.
An example of an output string:
amb=+100 alfa=+0.0120 vis=0250
The first figure – the amb parameter is uncalibrated measure of the ambient solar
irradiance in W/m2. The sensitivity depends strongly on how the sensor is aimed. It mayvary as much as -50 to +100%. But the repeatability is much better and the offset error
between units is only +/- 2. The sensor can, when mounted, be calibrated by comparing
it with an irradiance sensor. But a simple method is to take data from a clear day atnoon. If the sun is 60 deg or more above the horizon the irradiance is not far from 1000
W/m2. The measurement is not very accurate, but it may be useful for instance for telling
if it is day or night.
The second figure is the so-called extinction coefficient often called alfa. The relation
between the extinction and visibility is alfa=3/vis.* The alfa parameter can be used formonitoring trends in visibility when the visibility is larger than 1,000 meters. But note thatthe absolute accuracy in alfa is limited in such cases.
The third figure – the vis parameter – is the measured visibility in meters.
The displayed visibility will also be 1000 if the measured visibility is larger than 1000meters.

MiniBSV FAST Specifications
Dimensions（W*D*H）

68*34*45 mm

WeightAbout 170 g

Warm up time

About 10 seconds

Current consumption<50 mA DC12 Volt (8-14) supply

Outputs

Analog 0-5 V, and Digital RS232 19200bps

Update time

About 1 second

Operation Temp. range-20 to +50 deg C

Optical output power

About 3 mW (NIR LED) eye safe, class 1 M

Wavelength

850nm

Housing

Anodized aluminum, opening sealed with O-ringsVisibility range

2m – 1,000m

Mounting
The sensor should be mounted so that it "looks" horizontal and roughly north (south on
the southern hemisphere) – minimizing sunlight into receiver. There must not beanything in the sightline closer than 5 to 10 meters. Outside a cone of about 30 degrees
angle objects can be tolerated at down to 2 about meter. See figure below.

The outer dimensions are 68*45*34 mm and the four M3 holes for fastening are locatedon the top surface on a centered rectangle 14*51 mm.
We deliver a mounting bracket –seen in picture above - made of PMMA plastic. The
picture shows our solution for mounting on a vertical 42 mm dia. tube. The sensor iselectrically isolated when using this mounting bracket.
Mounting on a wall or too near to a roof of a building is not recommended. The reason isthat the air near a building is a little warmer than some meters away from it. And in thewarmer air the small “drops”will evaporate resulting in a higher measured visibility not
representative for the visibility in the area.
The sensor is delivered with a 6 meter 5-wire cable connected. The wire colors arechosen as follows:

redblack
whitegreen
yellow

12 Volt DC Power inPower ground
Signal ground
Digital signal out
Analog out