User manual VAISALA GMP343

[. . . ] USER'S GUIDE Vaisala CARBOCAP® Carbon Dioxide Probe GMP343 M210514EN-C PUBLISHED BY Vaisala Oyj P. O. Box 26 FIN-00421 Helsinki Finland Visit our Internet pages at http://www. vaisala. com/ © Vaisala 2007 No part of this manual may be reproduced in any form or by any means, electronic or mechanical (including photocopying), nor may its contents be communicated to a third party without prior written permission of the copyright holder. The contents are subject to change without prior notice. Please observe that this manual does not create any legally binding obligations for Vaisala towards the customer or end user. [. . . ] However, you can change the measurement range to optimize measurement performance for a certain concentration level. To achieve the most accurate 'ppm CO2' measurement, the measurement should be compensated for T, P, %RH, and O2 concentration in the environment. The compensation settings are specific to the selected measurement range, so selecting a suitable measurement range optimizes the compensation performance. Each range also has its own linearization function; see section Linearization on page 46. VAISALA _______________________________________________________________________ 41 User's Guide ______________________________________________________________________ There are 6 measurement ranges available. The range always begins with zero and only upper end value is changed. RANGE x SAVE x = 1. . . 6 Example: >range 4 1. SPAN (ppm) : : : : : : 1000. 00 2000. 00 3000. 00 4000. 00 5000. 00 20000. 00 RANGE : 4 > >save EEPROM saved successfully. NOTE RANGE-command only optimizes measurement. The scaling of the analog output is an independent issue. Normally it is necessary to change also ALOW and AHIGH values. For more information, see section, Setting and Testing the Analog Outputs, on page 52. Measurement Data Filtering The raw measurement values (measurement interval = 2 seconds) are an input to a chain of three filters: a median, an averaging, and a smoothing filter. The filters can be individually enabled or disabled by setting the filter coefficient to 0 (zero) or by choosing CO2RAW instead of CO2 for the measurement output quantity (see FORM command). Figure 8 Entering Measurement Values 42 __________________________________________________________________ M210514EN-C Chapter 4 ________________________________________________________________ Operation Median Filter Median filter is the first section in the filter chain, removing random peak values caused by external interference. The output of the median filter is the moving median of the values over the set number of measurements. The median filter arranges the values in the order of magnitude and outputs the middle value (not the average) if the number of the measurements is odd. In case an even number is set, the output is the average of the two middlemost measurements. The lowest reasonable set number of measurements is 3. Note that if the noise distribution is somewhat uniform the median filter does not give any additional value. The number of the measurements is set by the MEDIAN command. The default value is 0 (meaning that the median filter is disabled). Averaging Filter The averaging filter calculates a moving average over the user-set period of time. The longer the averaging time is the lower the noise at the measurement signal. For example, if the averaging is set to 30 seconds, the most recent average filter output is the average of the last 15 measurements (2 seconds measurement interval). The averaging time is set by the AVERAGE command. The default value is 10 seconds, and the maximum filter length is 60 seconds. [. . . ] Phone: +1 781 933 4500, Fax: +1 781 933 8029 E-mail: us-customersupport@vaisala. com EUROPEAN SERVICE CENTER Vaisala Instruments Service, Vanha Nurmijärventie 21 FIN-01670 Vantaa, FINLAND. Phone: +358 9 8949 2658, Fax: +358 9 8949 2295 E-mail: instruments. service@vaisala. com TOKYO SERVICE CENTER Vaisala KK, 42 Kagurazaka 6-Chome, Shinjuku-Ku, Tokyo 162-0825, JAPAN. Phone: +81 3 3266 9617, Fax: +81 3 3266 9655 E-mail: aftersales. asia@vaisala. com BEIJING SERVICE CENTER Vaisala China Ltd. , Floor 2 EAS Building, No. 21 Xiao Yun Road, Dongsanhuan Beilu, Chaoyang District, Beijing, P. R. [. . . ]