Data Sheet

Page 14 ams Datasheet
Document Feedback [v1-00] 2016-Jul-13
TCS3200, TCS3210 − Application Information
The output goes high upon the next subsequent pulse of the
principal frequency, beginning a new valid period. This
minimizes the time delay between a change on the input lines
and the resulting new output period. The response time to an
input programming change or to an irradiance step change is
one period of new frequency plus 1μs. The scaled output
changes both the full-scale frequency and the dark frequency
by the selected scale factor.
The frequency-scaling function allows the output range to be
optimized for a variety of measurement techniques. The
scaled-down outputs may be used where only a slower
frequency counter is available, such as low-cost
microcontroller, or where period measurement techniques are
used.
Measuring the Frequency
The choice of interface and measurement technique depends
on the desired resolution and data acquisition rate. For
maximum data-acquisition rate, period-measurement
techniques are used.
Output data can be collected at a rate of twice the output
frequency or one data point every microsecond for full-scale
output. Period measurement requires the use of a fast reference
clock with available resolution directly related to reference
clock rate. Output scaling can be used to increase the resolution
for a given clock rate or to maximize resolution as the light input
changes. Period measurement is used to measure rapidly
varying light levels or to make a very fast measurement of a
constant light source.
Maximum resolution and accuracy may be obtained using
frequency-measurement, pulse-accumulation, or integration
techniques. Frequency measurements provide the added
benefit of averaging out random- or high-frequency variations
(jitter) resulting from noise in the light signal. Resolution is
limited mainly by available counter registers and allowable
measurement time. Frequency measurement is well suited for
slowly varying or constant light levels and for reading average
light levels over short periods of time. Integration (the
accumulation of pulses over a very long period of time) can be
used to measure exposure, the amount of light present in an
area over a given time period.