EGM-5 Operation Manual V. 1.04 43 support@ppsystems.com
2
concentration (ppm) associated with the maximum Analog
Output voltage (2.5 V).
Returns to the Settings 2 Menu.
To change the CO
2
concentration represented by to the maximum analog output value, select the button
to the right of the “CO2
Conc (ppm):” text. The numerical keypad will appear, allowing a new number to
be entered.
In the example above, an analog output range of 0-2.5 volts corresponds to a CO
2
measurement range of
0-2,000 ppm. Again, the maximum analog output voltage is 2.5V.
After entering the desired value, press the “Back” button to return to the Settings 2 Menu.
Averaging Settings
This function allows the user to change/view the CO
2
averaging method used by the EGM-5.
The default EGM-5 averaging window is 1 second long. An optional running average function is available
to improve resolution and reduce the effect of transient fluctuations.
Running Average: The instrument’s response time to a step change is 2.5 seconds to reach 66% of a
new value, and 10 seconds to reach 99%, due to the time it takes samples to reach the IRGA. In other
words, if an instrument goes from measuring Sample Gas A to Sample Gas B, it would take 2.5 seconds
for the CO
2
reading to change by 66% of the difference between the two samples; after 10 seconds, the
measured value will be within 1% of the concentration of CO
2
in Sample Gas B. An exponential running
average algorithm can smooth out small fluctuations while remaining sensitive to larger differences. When
the running average is enabled (by setting Avg Limit greater than 0), the response time is 3.5 seconds to
reach 66% of a new value, and 16 seconds to reach 99%. A special feature of this running average
algorithm is that whenever a new reading differs from the current running average by more than the CO
2
Avg Limit value, a new running average begins. Thus, when the CO
2
concentration is changing rapidly,
averaging is suspended and the instrument can track changes at the basic instrument data rate of 1
second. When the CO
2
Avg Limit is set to 0, no running average is performed. The default CO
2
Avg Limit
is 30 ppm. The running average is applied to displayed data, recorded data, and analog output signals.
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