Retrotec DM-2 Operation Manual page 5

9.2 Check if wind is causing fluctuating pressure .................................................................... 46
9.2.1 Use the [@ Pressure] key to reduce the effects of wind ......................................................................... 46
9.2.2 Use Time Averaging feature to reduce the effects of wind ..................................................................... 47
[Time Avg] exercise to practice reducing the effects of wind .............................................................................. 47
9.2.3 Use Baseline feature to reduce the effects of a constant wind ............................................................... 47
[Baseline] exercise to practice minimizing the effects of wind ............................................................................ 47
9.2.4 In extreme cases you can use a Wind Damping Kit designed to reduce wind-related fluctuations........... 47
No cost wind damping procedure ...................................................................................................................... 48
9.3 Let Time Averaging take effect before making readings.................................................... 48
To learn how Time Averaging can cause error .................................................................................................... 49
9.4 Check if large fixed errors are caused by pinched tubes .................................................... 49
9.5 Check if large fixed errors are caused by water in the tube............................................... 49
9.6 Check if large fixed errors are caused by sun heating the tubes ........................................ 50
9.7 Results will be wrong if the Range and Device being used are different than those selected
on the gauge .................................................................................................................................. 50
To determine correct flow if Range selected was different than the actual Range used: ..................................... 50
9.8 Fans without reference tube have results adjusted by gauge ........................................... 51
9.9 Pressure can overshoot when using the Set Pressure key ................................................. 51
9.10 Keep the Keep Rechargeable Batteries in top shape ......................................................... 52
To charge the batteries: ..................................................................................................................................... 52
9.11 If the Serial Number and Calibration Date are not valid .................................................... 53
9.12 If the keys on the DM-2 Keypad are not working .............................................................. 53
To fix the keypad if the keypad cable has come loose and keys are not working ................................................. 53
9.13 Updating Firmware ............................................................................................................ 54
9.13.1 Firmware Changes ............................................................................................................................ 54
Table 10: Firmware changes from versions prior to 2.29 to the current version 3.01b. ....................................... 54
Appendix A: The gauge calculates Flow based on Pressure readings from the fan ..... 56
To determine the flow for a particular fan pressure FP: ...................................................................................... 57
Check that the measured value for FP meets the two conditions based on MF and K2. If so, find the N, K, K1, and
K3 values in Table xxx (based on the type of fan and the Range Configuration being used), enter those values
along with the values measured for FP, and RP into the Flow equation stated above and calculate the result. .... 57
Appendix B: Manually calculate Flow if required test pressure cannot be reached .... 60
Cannot Reach 50 Pa Factors .......................................................................................................... 60
Cannot Reach 25 Pa Factors .......................................................................................................... 61
Appendix C: Errors occur in estimated flow if gauge and actual "n" don't match ....... 63
Appendix D: Adjust Flow values for temperature difference ...................................... 65
Appendix E: Tables to correct Flow if range selected did not match installed range .. 67
Appendix F: Setting up for a test with Alaska's AkWarm software .............................. 69
Glossary ......................................................................................................................... 70
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