58 CBLé System Guidebook
TI Probes
About the Light Probe
The TI light probe uses a phototransistor to measure irradiance. The
units of irradiance are milliwatts or microwatts per square centimeter.
The light probe’s output is a voltage that is linearly proportional to the
amount of irradiance it senses. The range of light over which the probe is
sensitive is 10µW/cm
2
to 1mW/cm
2
.
The
AutoIDENT
resistor in the probe causes the CBL software to
automatically convert the measured voltage to mW/cm
2
units. The probe
is direction dependent and achieves the highest output when the end of
the probe is pointed directly at the light source.
The light probe is sensitive in the visible and near-infrared (
IR
) light
range. This means you can use it with
IR
emitting diodes as well as all
visible light sources. The light probe is designed to work in air only—it is
not waterproof.
Light Probe Specifications
Channels Connects to
CH1
,
CH2
,
CH3
(analog
channels)
Current drain 5 mA max.
Voltage range 0–5 Volts
Irradiance range 10µW/cm
2
to 1mW/cm
2
Spectral response range 300nm to 1100nm (nanometers) (non-flat
response)
Chemical tolerance None (air only)
Conversion equation
Coefficients
(units = mW/cm
2
)
Irradiance = (K
0
* voltage) + K
1
K
= 0.198795
K
1
= 0.00602410
Accuracy ±20% (Calibrated to a tungsten lamp. Using
other light sources will return irradiance <
actual.)
Pins used 2 ground
4
AutoIDENT
resistor
5 +5 Volts DC
6 Signal
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