using only 1 orifice with DAQ - will it work?

[106-1194218389]

We have discussed whether or not you can get away with using only one large range orifice when using an Digital Manometer compared to a water manometer. I know that when you use the water manometers you DO have to use each range of orifice trying to keep the flow above the 50% range of the orifice as they have a sweet spot. The following is a comparison between a flow test using the full range of orifices and just using the largest orifice I have. Test on left is using my full range of orifices keeping the test above 50% and the test on the right is using only my top range orifice. You be the judge. btw I am using the Performance Trends Black Box.

all orifices 1 orifice only for all flows
.050" 33.0 cfm .050" 33.7 cfm
.100" 65.8 cfm .100" 69.1 cfm
.150" 103.4 cfm .150" 103.0 cfm
.200" 132.3 cfm .200" 134.4 cfm
.250" 161.7 cfm .250" 163.0 cfm
.300" 185.9 cfm .300" 186.5 cfm
.350" 211.0 cfm .350" 211.3 cfm
.400" 227.5 cfm .400" 226.1 cfm
.450" 242.1 cfm .450" 241.7 cfm
.500" 251.8 cfm .500" 252.2 cfm
.550" 259.8 cfm .550" 259.0 cfm
.600" 262.0 cfm .600" 261.9 cfm
.650" 263.3 cfm .650" 262.8 cfm
.700" 263.5 cfm .700" 262.3 cfm
.750" 261.8 cfm .750" 259.9 cfm
.800" 260.3 cfm .800" 261.8 cfm

[MrHijet]

It's pretty precise in the range above 160 cfm.

What orifices have you used for the water manometer and which single one for the digital ?

Cheers,

Daniel

[49-1183904562]

[color=#000000]John I find your comparison quit timely as just yesterday I was trying to talk Bruce into working with me on a set of plans for a Mini bench top bench, 2 to 3 motor, speed control for depression and electronics only. I stole the idea from Rusty

[106-1194218389]

[color=#000000][quote="1960FL"]John I find your comparison quit timely as just yesterday I was trying to talk Bruce into working with me on a set of plans for a Mini bench top bench, 2 to 3 motor, speed control for depression and electronics only. I stole the idea from Rusty

[106-1194218389]

[MrHijet]

No need for checking. Your answer to Rick already explained everything.

Cheers,

Daniel

[106-1194218389]

Here is an update. What I did was another test run tonight 10/29/08 with just one orifice. You will notice that there are a couple of flows where there was a change of around 4 cfm where as the other lifts were pretty darn close. I think what this may be more than anything is my valve opening device not being able to be exactly duplicating. It is very close, but as we have discussed using a digital manometer can pick up very small changes and I mean small. I changed the opening just .002" and it picked it up. was at least 1 to 1.5 cfm different. Keep that it mind when using a DAQ you will have to have something that is very repeatable to the thou for opening and closing valves. When you are using the water manometer it would not show that very well. Here are the flow comparisons. All flows with just one orifice and it is the same one in all tests. The worse difference at one lift was 1.9% and the best was 0%. I figured the average difference for all lifts was around .6%. Not too shabby for a homemade unit using 2 shop vacs. Now with a super precision valve opener and some of Bruce's orifices and I bet it will be much closer!

1 orifice 10/29/08 1 orifice 10/28/08
.050" 34.2 cfm .050" 33.7 cfm
.100" 69.5 cfm .100" 69.1 cfm
.150" 102.5 cfm .150" 103.0 cfm
.200" 133.2 cfm .200" 134.4 cfm
.250" 162.4 cfm .250" 163.0 cfm
.300" 187.2 cfm .300" 186.5 cfm
.350" 207.4 cfm .350" 211.3 cfm
.400" 226.3 cfm .400" 226.1 cfm
.450" 241.5 cfm .450" 241.7 cfm
.500" 252.1 cfm .500" 252.2 cfm
.550" 258.9 cfm .550" 259.0 cfm
.600" 262.0 cfm .600" 261.9 cfm
.650" 262.4 cfm .650" 262.8 cfm
.700" 262.0 cfm .700" 262.3 cfm
.750" 259.9 cfm .750" 259.9 cfm
.800" 257.3 cfm .800" 261.8 cfm