7. Perform 5 runs to determine an average. Pass/fail criteria is ±1.0% for the measurement of uncertainty. If not passing, adjust and repeat the test. After adjusting the pressure in the green tank to zero using the water valve, measure the amount of water in the green tank with the ruler. (Typically around 22 inches ± 1 inch) Interpolate this measurement to the nearest 1/32 of an inch and convert to decimal. This figure is used in the Spirometer Calibration program found where these instructions were located. Enter this number into the spreadsheet and the final DGM number after the run. 5. Plug the manometer hose on the green tank. Turn the water valve on (to start water flowing into the green tank). (The sample rate is usually set on a "set up" run, as the first run will not be used in the calibrations.) Enter the initial DGM reading into the spreadsheet. Sample 1 cubic foot as near as possible then pinch off hose leading from the Spirometer (this prevents the DGM from being driven backwards) and quickly go out to the Spirometer and close the water valve. While sampling, include the barometric pressure, Spirometer temperature, meter temperature and meter pressure (from the manometer) into the spreadsheet. 6. Without removing the hose clamp at the meter, lower the red tank and adjust the water in the green tank using the water valve so there is no pressure in the green tank. This requires you to unplug the left manometer hose. Do this with care, as there might be enough pressure to either blow the fluid out of the hose or draw it into the green tank. Adjust the pressure in the constant volume tank (green) using the water valve. Normally you have to add water to the constant volume tank to equalize the pressure but if you go too far, it will be necessary to lower the red tank and allow some water out of the green tank. This takes some practice. 4. Raise the red tank above the green tank. Plug the manometer on the green tank. (Plugging the manometer hose when transferring water in either direction keeps the fluid in the manometer from being forced either out of the hose or into the green tank.) Using the water valve adjust the water in the green tank just enough to be able to adjust the ruler up or down to zero the ruler with the water level. Set the ruler bottom at the top of the meniscus. Unplug manometer slowly on green tank and using the water valve, toggle on and off until the manometer on the green tank shows no pressure at all. The fluid in the two tubes will be level when there is no pressure in the green tank. Leave the clamp open and reset the ruler if necessary. At this point, clamp open, water off, manometer levels the same and the ruler at the top of the meniscus in the water level vial, you are ready to start sampling.
Following the successful calibration of this piece of equipment a calibration sticker shall be attached to the instrument.
Measurement Uncertainty is calculated using the following formula: O.M.U. = k*((A.D.)2 + (S.D.)2 + (R.M.U.)2)1/2 O.M.U. = Overall Measurement Uncertainty A.D. = Average Deviation of the percent difference of all measured results compared to the reference value. S.D. = Standard Deviation of the percent difference of all measured results compared to the reference value. k = Confidence Factor (2 for 95% confidence) R.M.U. = Standard Measurement Uncertainty of Reference Measurement Equipment. R.M.U. is considered as the measurement uncertainty as stated on calibration certificates of equipment, or the tolerance listed in the calibration standard of the test equipment
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