Retrotec DM32 Manuel d'utilisateur télécharger pdf (Page 6)

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8.8 Calculated Result will be wrong if the Range and Device installed on fan are different than those

selected on the gauge ................................................................................................................................. 61

8.9 Moving tubes might cause fluctuating pressure readings ............................................................. 61

8.10 Fans with a single tube have results adjusted by gauge ................................................................ 62

8.11 Pressure can overshoot when using the Set Pressure key ............................................................. 62

8.12 Check if large fixed errors are caused by pinched tubes ................................................................ 63

8.13 Check if large fixed errors are caused by water in the tube ........................................................... 64

8.14 Check if large fixed errors are caused by sun heating the tubes.................................................... 65

8.15 Check if wind is causing fluctuating pressure ................................................................................. 65

8.15.1. Use the [@ Pressure] key to reduce the effects of wind ....................................................... 65

8.15.2. Use Time Averaging feature to reduce the effects of wind ................................................... 65

8.15.3. Let Time Averaging take effect before making readings ....................................................... 65

8.15.4. Use Baseline feature to reduce the effects of a constant wind ............................................ 66

8.15.5. In extreme cases you can use a Wind Damping Kit designed to reduce wind-related

fluctuations ............................................................................................................................................. 66

9. Technical Specifications ................................................................................. 68

Appendix A: Understanding Pressures on the Gauge ........................................... 70

Differential Pressure .................................................................................................................................... 70

Positive vs. Negative Pressure ..................................................................................................................... 70

Why static and fluctuating pressures occur, causing bias ........................................................................... 71

Managing fluctuating pressures created by wind ....................................................................................... 72

Reduce uncertainty in results by taking lots of readings ............................................................................ 72

Appendix B: Flow Equations used with Devices ................................................... 74

Appendix C: Manually estimate Flow if required test pressure cannot be reached

............................................................................................................................ 79

Cannot Reach 50 Pa Factors ........................................................................................................................ 80

Cannot Reach 25 Pa Factors ........................................................................................................................ 81

Appendix D: Details about the @Pressure extrapolation function ....................... 82

“n value” for @Pressure extrapolation ....................................................................................................... 83

Errors occur in estimated flow if gauge and actual “n” don’t match .......................................................... 84

Appendix E: Tables to adjust Flow values for temperature difference ................. 87

Appendix F: Tables to correct Flow if range selected did not match the installed

range ................................................................................................................... 89

Appendix G: Measure Supply or Exhaust flow with a gauge and box .................. 90

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Retrotec DM32 Manuel d'utilisateur Page 6

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