SF Sizes

[Chad Speier]

I'll be interested in the gage oil comparison. Zeroing the manometers like they want you to.

I understand I calibrated with the same plate and same processor. However, the plate is a MUST and I personally think that is the entire issue. They don't calibrate it properly. Like I said, being linear is more important and it passed with an A++..

[blaktopr]

Thats great info and love the responses.

Must be the use of Bruce's plates that keep the measuring more linear as airspeeds increase through the measuring orifice.

Chad, if anything, looking at 5 cfm difference? The others must be in an uproar due to a larger difference and/or their stuff backing up at .6/.700.

Oh, and as for the DC using PTS plates and digital manometer. In my bench with LARGE chambers and adjusting the air and water variables in the config window to current temp, the DC approaches .62 like the plate's.

[Chad Speier]

OK Guys...

Got the blue gage oil and did it exactly like the manual says. Small hole flowed 22% and both holes on #4 flowed 240cfm.

I then put my 2.250 plate (356 calibrated cfm w/electronics) and it showed 78.2% of 442.9cfm = 346.3 cfm

Then I flowed the head..

.200 145.9
.300 215.3
.400 256.5
.500 289.6
.600 307.4
.700 314.8
.800 316.6
.900 318.4
1.00 322.8

[jfholm]

What I would like to see is someone "t" into the hi pressure and low pressure taps for the inclined manometer with a vertical manometer. Put a head on and then choose an orifice to where you could get a 100% reading at your test pressure. 25" or 28" whatever you are using, and see what the actual Delta pressure is. I think Bruce's DM is set to 16" correct Bruce? Maybe SF is calibrating at the wrong Delta pressure.

John

[1960FL]

Chad, I would have to agree with John, it would be nice to know the true DP in inches of water,

The PTS DM can do this if yo do not have a water manometer laying around. Something just does not sound right.

Rick

[Chad Speier]

I can use the extra manometer on the bench.

Won't my FP1 do this? I think I have done this on my PTS. Just don't remember how I did it, LOL.

[jfholm]

Chad,
I am sure it will work. Just hook up the test pressure from your FP1 via t's to the inclined taps on the flow bench and it should work. It will show the Delta P as a test pressure reading but we will know that is the true delta p. I first discovered that when I was setting up my Black Box from Performance Trends. It did not match what the water manometers were reading because when I set the black box up I had entered a Delta P lower that what I really had. Once I had entered the real DP in the setup then it matched what the water manometer was reading.

John

[Chad Speier]

Chad,
I am sure it will work. Just hook up the test pressure from your FP1 via t's to the inclined taps on the flow bench and it should work. It will show the Delta P as a test pressure reading but we will know that is the true delta p. I first discovered that when I was setting up my Black Box from Performance Trends. It did not match what the water manometers were reading because when I set the black box up I had entered a Delta P lower that what I really had. Once I had entered the real DP in the setup then it matched what the water manometer was reading.

John

I was thinking I just put the FP in manometer mode. I will check it all out tomorrow.

[Brucepts]

Yes, my DM uses a 16" sensor on the CFM channel

[Brucepts]

On the PTS DM you can change a channel calibration # which allows you to dial in the linearity of the sensor, this is done in my shop for each DM model but, can be tweaked in the field (not recommended). It allows up to 8 decimal places of tweakness which is way more than any normal person requires trust me on this one

I use a water gage and compare the DM scale readings at various water readings and then use a set of plates from 25-600 cfm with various internal plate ranges. I tweak the channel calibration till everything matches to get a final calibration factor and there is a label on each DM showing this number. Each model requires a different calibration number. We now have 3 models of the 40" DM in the field. So each DM has a slightly different scale length on the configuration, so they might show a different Cd once the bench is finally calibrated, tweaking the channel calibration is not a good thing so the Cd is there fore changed. You want the scale to be linear and if you go playing around with that calibration factor you are not going to have a linear scale.

Now to further this discussion you could set the calibration factor to assure you have each plate reading it's rated cfm number and have a non-linear scale (been there tried this) but I do not recommend this as each internal plate would require a different calibration and it's much easier to deal with the Cd. Not a road I want to go down on discussing so please understand it's been tried and discussed to death already

On a fixed incline manometer you can't tweak the scale so you are kind of stuck with whatca got, one plus for digital you can tweak the scale! The scale has to stay at the same rise even if it does not match what is required for it to be linear. OS you can not tweak your scale based on size differences of your internal orifice plate, so any differences in hole sizes between flowbenches can not be accounted for other than through math. Hence, the reason you see SF flowbenches reading different numbers?

The level of tweakness built into the PTS DM within Flowsoft by Rick is pretty much above the level of what anyone else allows on their digital product! Rick and I have gone back and forth on this subject many times for hours on end trust me on this! He wins the discussion everytime