Analog Devices EVAL-ADPD188BIZ-SK, Руководство пользователя

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UG-1274 EVAL-ADPD188BIZ-SK User Guide
Rev. 0 | Page 6 of 10
3. With the sensor board in a fixed position and no aerosol or
smoke in the optical path, run the WaveTool by pressing
the play button. The raw data view,
Slot A/B vs Time , must
be at some average level. This average level must be nulled
out before measuring smoke or aerosol, as described in the
following steps (Step 4 to Step 6).
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015
Figure 15. Average Value Prior to Nulling Offset
4. Open the Statistics window by clicking the Statistics
button in the data view.
5. In the Statistics window, select Continuous Update . Allow
the Statistics window to calculate the mean value. After a
mean value is calculated, click the Subtract mean from
Offsets button.
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016
Figure 16. Statistics Window
6. In the data view, click the Null Offset button to set
the Time Slot A and Time Slot B raw data values to
approximately zero, plus or minus the noise that may
be present (see Figure 17).
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7
Figure 17. Data View Following Null Offset
After these steps are complete, the user can begin testing with
different aerosols. Figure 19 shows the raw output data, as well
as the blue/IR ratio of the response to a jet of smoke spray. The
EN_MW button can be pressed to enable an eight point moving
average filter on the data being plotted.
The settings can be further optimized by manipulating the LED
drive currents, the transimpedance amplifier (TIA) gain, the
number of pulses, and the decimation rate until the desired
signal-to-noise ratio (SNR) is obtained from the response to the
smoke or aerosol being detected. For information about optimizing
the
ADPD188BI , refer to the ADPD188BI data sheet. For
functional descriptions of the Applications WaveTool , refer to
the Applications WaveTool user guide provided in the software
package download.