R36US0002EU0100 Rev 1.00
Page 11
Aug 26, 2021
RTD120D-EVK Evaluation Kit Software Manual
6. The amount of change of the raw value in the last several samples is displayed in the plot labeled “Variation
(peak-to-peak)”. In this plot, there is a normal (green) and a magnified (blue) trace.
These peak-to-peak values get updated every 5 seconds or so, which is the normal sample period. Watch the
blue trace as it goes down in value until it dips below 1.0. This should complete in a minute or two. If the
peak
-
to-peak variation never dips below 1.0, then just wait until it stabilizes around a certain value. It will
change a bit continually but only by a small amount
7.
Advanced Operation
: If you learn and understand the effect of adjusting the digital filter stages while you are
watching the raw value change, you can use them to save some time in this part of the procedure. The filter
buttons can be used to change the number of samples used in the two digital filter stages in order to speed up
the convergence of the raw value (and also the calculated CO
2
concentration value) to a steady reading. If you
use these buttons, be sure to restore the filter settings to the
default
values (shown with button text in
green
).
The left column of buttons (“Fa: #”) sets the number of samples used in the first filter stage, which filters A/D
readings (that is, it filters the difference between CO
2
and Reference A/D readings). The right column (“F: #”)
is for the second filter stage, which filters raw readings after the
log(I/I
0
)
function has been applied.
8. Once the peak-to-peak variation is below 1.0 (or stabilizes slightly about that value), store the raw value by
clicking the “Set” button associated with the CO
2
concentration you are currently calibrating. For example, for
1000ppm CO
2
, click:
