DIY measurement of low pressure?


I want to measure changes in air pressure in the under 10 pascal range. I'm interested in relative measurements, so absolute accuracy is not an issue.
I have a digital manometer, but it has resolution of only 2 pascals. I'd like to have maybe 10x that resolution.
If my math is correct, a pascal is about .004" of water. I made a quick attempt to build an inclined tube manometer with water. Surface tension of the water is greater than the pressure being measured. Tried dishwasher soap as a surfactant (cause it was handy) without success.
Next experiment is to blast a tiny air jet onto something light like gold leaf??
Any ideas on how to fashion a temporary gizmo to do what I want? Thanks, mike
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If you haven't already, check out the wikipedia article "Pressure Measurement" for ideas.
On 5/7/2010 7:53 AM, mike wrote:

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Cas-Environ LLC Palisades Park, New Jersey Ph: 201-944-6294 *** Fx: 201-944-9053 General Altitude Pressure Conversion Chart line feet meter in Hg torr mbar psia deg C deg F line feet meter in Hg torr mbar psia deg C deg F 1 -1000 -304.8 31.02 787.9 1051.50 15.25 17.0 62.6 68 32500 9906.0 7.910 201.00 268.21 3.890 -49.4 -56.9 2 -500 -152.4 30.47 773.8 1030.10 14.94 16.0 60.8 69 33000 10058.4 7.730 196.40 262.01 3.800 -50.4 -58.7 3 0 0.0 29.92 760.0 1013.50 14.70 15.0 59.0 70 33500 10210.8 7.750 191.80 255.80 3.710 -51.4 -60.5 4 500 152.4 29.38 746.4 994.95 14.43 14.0 57.2 71 34000 10363.2 7.380 187.40 250.29 3.630 -52.4 -62.3 5 1000 304.8 28.86 732.9 977.71 14.18 13.0 55.4 72 34500 10515.6 7.200 183.00 244.08 3.540 -53.4 -64.1 6 1500 457.2 28.33 719.7 958.40 13.90 12.0 53.6 73 35000 10668.0 7.040 178.70 238.57 3.460 -54.3 -65.8 7 2000 609.6 27.82 706.6 942.55 13.67 11.0 51.8 74 35500 10820.4 6.870 174.50 232.71 3.375 -55.0 -67.0 8 2500 762.0 27.31 693.8 924.62 13.41 10.0 50.0 75 36000 10972.8 6.710 170.40 227.36 3.296 -55.0 -67.0 9 3000 914.4 26.81 681.1 909.45 13.19 9.1 48.4 76 36500 11125.2 6.550 166.40 222.02 3.220 -55.0 -67.0 10 3500 1066.8 26.32 668.6 890.83 12.92 8.1 46.6 77 37000 11277.6 6.390 162.40 216.50 3.140 -55.0 -67.0 11 4000 1219.2 25.84 656.3 875.66 12.70 7.1 44.8 78 37500 11430.0 6.240 158.60 211.45 3.067 -55.0 -67.0 12 4500 1371.6 25.36 644.2 854.43 12.45 6.1 43.0 79 38000 11582.4 6.100 154.90 206.44 2.994 -55.0 -67.0 13 5000 1524.0 24.89 632.3 843.26 12.23 5.1 41.2 80 38500 11734.8 5.950 151.20 201.68 2.925 -55.0 -67.0 14 5500 1676.4 24.43 620.6 827.48 12.00 4.1 39.4 81 39000 11887.2 5.810 147.60 196.65 2.852 -55.0 -67.0 15 6000 1828.8 23.98 609.0 811.54 11.77 3.1 37.6 82 39500 12039.6 5.680 144.10 192.92 2.798 -55.0 -67.0 16 6500 1981.2 23.53 597.6 797.06 11.56 2.1 35.8 83 40000 12192.0 5.540 140.70 187.54 2.720 -55.0 -67.0 17 7000 2133.6 23.09 586.4 781.89 11.34 1.1 34.0 84 40500 12344.4 5.410 137.40 183.41 2.660 -55.0 -67.0 18 7500 2286.0 22.65 575.3 766.72 11.12 0.1 32.2 85 41000 12496.8 5.280 134.20 178.93 2.595 -55.0 -67.0 19 8000 2438.4 22.22 564.4 751.55 10.90 -0.8 30.7 86 41500 12649.2 5.160 131.00 174.79 2.535 -55.0 -67.0 20 8500 2590.8 21.80 553.7 737.77 10.70 -1.8 28.8 87 42000 12801.6 5.040 127.90 170.31 2.470 -55.0 -67.0 21 9000 2743.2 21.38 543.2 723.97 10.50 -2.8 27.0 88 42500 12954.0 4.920 124.90 166.51 2.415 -55.0 -67.0 22 9500 2895.6 20.98 532.8 710.18 10.30 -3.8 25.2 89 43000 13106.4 4.800 122.00 162.72 2.360 -55.0 -67.0 23 10000 3048.0 20.58 522.6 696.39 10.10 -4.8 23.4 90 43500 13258.8 4.690 119.10 158.86 2.304 -55.0 -67.0 24 10500 3200.4 20.18 512.5 683.29 9.91 -5.8 21.6 91 44000 13411.2 4.560 116.30 155.14 2.250 -55.0 -67.0 25 11000 3352.8 19.79 502.6 670.88 9.73 -6.8 19.8 92 44500 13563.6 4.470 113.50 151.35 2.195 -55.0 -67.0 26 11500 3505.2 19.40 492.8 657.09 9.53 -7.8 18.0 93 45000 13716.0 4.360 110.80 147.55 2.140 -55.0 -67.0 27 12000 3657.6 19.03 483.3 644.68 9.35 -8.8 16.2 94 45500 13868.4 4.260 108.20 144.38 2.094 -55.0 -67.0 28 12500 3810.0 18.65 473.8 630.89 9.15 -9.8 14.4 95 46000 14020.8 4.160 105.70 140.80 2.042 -55.0 -67.0 29 13000 3962.4 18.29 464.5 618.48 8.97 -10.8 12.6 96 46500 14173.2 4.060 103.20 137.69 1.997 -55.0 -67.0 30 13500 4114.8 17.93 455.4 607.45 8.81 -11.7 10.9 97 47000 14325.6 3.970 100.70 134.31 1.948 -55.0 -67.0 31 14000 4267.2 17.57 446.4 595.04 8.63 -12.7 9.1 98 47500 14478.0 3.873 98.38 131.00 1.900 -55.0 -67.0 32 14500 4419.6 17.22 437.5 583.32 8.46 13.7 7.3 99 48000 14630.4 3.781 96.05 128.11 1.858 -55.0 -67.0 33 15000 4572.0 16.88 428.8 570.91 8.28 -14.7 5.5 100 48500 14782.8 3.693 93.79 125.01 1.813 -55.0 -67.0 34 15500 4724.4 16.54 420.2 560.56 8.13 -15.7 3.7 101 49000 14935.2 3.605 91.57 122.18 1.772 -55.0 -67.0 35 16000 4876.8 16.21 411.8 548.84 7.96 -16.7 1.9 102 49500 15087.6 3.520 89.41 119.21 1.729 -55.0 -67.0 36 16500 5029.2 15.89 403.5 538.50 7.81 -17.7 0.1 103 50000 15240.0 3.436 87.30 116.46 1.689 -55.0 -67.0 37 17000 5181.6 15.56 395.3 526.78 7.64 -18.7 -1.7 104 51000 15544.8 3.276 83.22 111.01 1.610 -55.0 -67.0 38 17500 5334.0 15.25 387.3 516.43 7.49 -19.7 -3.5 105 52000 15849.6 3.124 79.34 105.70 1.533 -55.0 -67.0 39 18000 5486.4 14.94 379.4 506.09 7.34 -20.7 -5.3 106 53000 16154.4 2.978 75.64 100.87 1.463 -55.0 -67.0 40 18500 5638.8 14.63 371.7 495.75 7.19 -21.7 -7.1 107 54000 16459.2 2.839 72.12 96.19 1.395 -55.0 -67.0 41 19000 5791.2 14.33 364.0 485.41 7.04 -22.6 -8.7 108 55000 16764.0 2.707 68.76 91.70 1.330 -55.0 -67.0 42 19500 5943.6 14.04 356.5 475.75 6.90 -23.6 -10.5 109 56000 17068.8 2.581 65.55 87.50 1.269 -55.0 -67.0 43 20000 6096.0 13.75 349.1 465.41 6.75 -24.6 -12.3 110 57000 17373.6 2.460 62.49 83.29 1.208 -55.0 -67.0 44 20500 6248.4 13.46 341.9 445.76 6.61 -25.6 -14.1 111 58000 17678.4 2.346 59.58 79.43 1.152 -55.0 -67.0 45 21000 6400.8 13.18 334.7 446.79 6.48 -26.6 -15.9 112 59000 17983.2 2.236 56.80 75.71 1.098 -55.0 -67.0 46 21500 6553.2 12.90 327.7 437.14 6.34 -27.6 -17.7 113 60000 18288.0 2.132 54.15 72.26 1.048 -55.0 -67.0 47 22000 6705.6 12.63 320.8 428.18 6.21 -28.6 -19.5 114 61000 18592.8 2.033 51.63 68.95 1.000 -55.0 -67.0 48 22500 6858.0 12.36 314.1 419.22 6.08 -29.6 -21.3 115 62000 18897.6 1.938 49.22 65.64 0.952 -55.0 -67.0 49 23000 7010.4 12.10 307.4 409.57 5.94 -30.6 -23.1 116 63000 19202.4 1.847 46.92 62.47 0.906 -55.0 -67.0 50 23500 7162.8 11.84 300.9 401.29 5.82 -31.6 -24.9 117 64000 19507.2 1.761 44.73 59.64 0.865 -55.0 -67.0 51 24000 7315.2 11.59 294.4 393.01 5.70 -32.5 -26.5 118 65000 19812.0 1.679 42.65 56.88 0.825 -55.0 -67.0 52 24500 7467.6 11.34 288.1 384.74 5.58 -33.5 -28.3 119 66000 20116.8 1.601 40.66 54.19 0.786 -55.0 -67.0 53 25000 7620.0 11.10 281.9 375.78 5.45 -34.5 -30.1 120 67000 20421.6 1.526 38.76 51.57 0.748 -55.0 -67.0 54 25500 7772.4 10.86 275.8 367.50 5.33 -35.5 -31.9 121 68000 20726.4 1.455 36.95 49.23 0.714 -55.0 -67.0 55 26000 7924.8 10.62 269.8 359.92 5.22 -36.5 -33.8 122 69000 21031.2 1.387 35.23 46.95 0.681 -55.0 -67.0 56 26500 8077.2 10.39 263.9 352.33 5.11 -37.5 -35.5 123 70000 21336.0 1.322 33.59 44.75 0.649 -55.0 -67.0 57 27000 8229.6 10.16 258.1 344.06 4.99 -38.5 -37.3 124 71000 21640.8 1.261 32.02 42.68 0.619 -55.0 -67.0 58 27500 8382.0 9.94 252.5 336.48 4.88 -39.5 -39.1 125 72000 21945.6 1.202 30.53 40.68 0.590 -55.0 -67.0 59 28000 8534.4 9.72 246.9 329.58 4.78 -40.5 -40.9 126 73000 22250.4 1.146 29.10 38.75 0.562 -55.0 -67.0 60 28500 8686.8 9.50 241.4 322.00 4.67 -41.5 -42.7 127 74000 22555.2 1.093 27.75 36.95 0.536 -55.0 -67.0 61 29000 8839.2 9.29 236.0 314.41 4.56 -42.5 -44.5 128 75000 22860.0 1.041 26.45 35.30 0.512 -55.0 -67.0 62 29500 8991.6 9.08 230.7 307.52 4.46 -43.4 -46.1 129 76000 23164.8 0.993 25.22 33.65 0.488 -55.0 -67.0 63 30000 9144.0 8.88 225.6 300.62 4.36 -44.4 -47.9 130 77000 23469.6 0.946 24.04 32.06 0.465 -55.0 -67.0 64 30500 9296.4 8.68 220.5 294.42 4.27 -45.4 -49.7 131 78000 23774.4 0.902 22.92 30.54 0.443 -55.0 -67.0 65 31000 9448.8 8.48 215.5 287.52 4.17 -46.4 -51.5 132 79000 24079.2 0.860 21.85 29.17 0.423 -55.0 -67.0 66 31500 9601.2 8.29 210.6 280.63 4.07 -47.4 -53.3 133 80000 24384.0 0.820 20.83 27.79 0.403 -55.0 -67.0 67 32000 9753.6 8.10 205.8 274.42 3.98 -48.4 -55.1 134 85000 25908.0 0.647 16.44 21.90 0.318 -55.0 -67.0 COURTESY OF YOUR SERVICE COMPANY
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