Air density gauge

[Don Ferrette]

Last comment on this. I forwarded this "debate" to a old friend last night before I went to bed. He is a seasoned pilot with flight experience in everything from a Cessna to an F14 (retired military). Here is his reply-

"Don

While it is an interesting angle that this friend of yours is using the first question I have to ask is ...why? When flying it is very important have as much accurate, updated data as possible as the conditions in which one flies the variables are ever changing. Different altitudes, weather zones, air speeds, etc. all play a role in planning and executing a safe flight plan. You're not flying a plane, your altitude does not change nor does your location. Even a fast moving weather front is not going affect what you do that quickly compared to flying that a density guage can't handle. True, you can get the same or similar results but if your going to trust something used or off some place like Ebay without having it checked & calibrated you might find yourself shooting in the dark. Ask yourself why that used altimeter is on Ebay in the first place & not still in a plane. So by the time you purchase a used altimeter, have it's calibration checked, & then the "high quality" thermometer as your friend refers to you'll probably have more invested than the cost of one density guage. So why go through all that?"

If your set up makes you happy then that is great. I've always been a big fan of keeping it simple which one guage does for me. B)

 

[Joe_Knesek]

Last comment on this. I forwarded this "debate" to a old friend last night before I went to bed. He is a seasoned pilot with flight experience in everything from a Cessna to an F14 (retired military). Here is his reply-"Don

While it is an interesting angle that this friend of yours is using the first question I have to ask is ...why? When flying it is very important have as much accurate, updated data as possible as the conditions in which one flies the variables are ever changing. Different altitudes, weather zones, air speeds, etc. all play a role in planning and executing a safe flight plan. You're not flying a plane, your altitude does not change nor does your location. Even a fast moving weather front is not going affect what you do that quickly compared to flying that a density guage can't handle. True, you can get the same or similar results but if your going to trust something used or off some place like Ebay without having it checked & calibrated you might find yourself shooting in the dark. Ask yourself why that used altimeter is on Ebay in the first place & not still in a plane. So by the time you purchase a used altimeter, have it's calibration checked, & then the "high quality" thermometer as your friend refers to you'll probably have more invested than the cost of one density guage. So why go through all that?"

If your set up makes you happy then that is great. I've always been a big fan of keeping it simple which one guage does for me. B)

Don, your friend has made a few incorrect assumptions about my gauges.

1. I didn't get them off of ebay. I only refered others to ebay.
   
2. My father-in-law, who was a Master Aviator and a Sr. Flight Inspector, gave me the gauges that came from a friend's helicopter that was retired because of air frame damage caused by a rotor strike.
   
3. Both gauges were calibrated the year I got them.
   
4. As Terry explained in his post, I leave it set at 29.92Hg and using the altimeter to measure the pressure change not altitude.
   
5. Again, it's a good alternative to a density guage that is capable of producing the same results.
   

 

[Don Ferrette]

Joe- Gary (that's his name btw) did not make incorrect assumptions, he replied to the advice you gave on where someone can get used ones. The fact you obtained your gauges in the matter you did is irrelevant as you advise people to look at sources for used ones such as Ebay so his point is quite valid.

"Again, it's a good alternative to a density guage that is capable of producing the same results."

On this I will agree if someone is as fortunate as you to obtain used stuff with a known documented history.

O/B sorry your simple question as to where to buy a density guage got so sidetracked.

 

[Joe_Knesek]

Joe- Gary (that's his name btw) did not make incorrect assumptions, he replied to the advice you gave on where someone can get used ones. The fact you obtained your gauges in the matter you did is irrelevant as you advise people to look at sources for used ones such as Ebay so his point is quite valid.
"Again, it's a good alternative to a density guage that is capable of producing the same results."

On this I will agree if someone is as fortunate as you to obtain used stuff with a known documented history. B)

I'd argue that a used altimeter Mil-Spec out of calibration is still better calibrated than the air density guage you are refering to. As I said, in side by side comparisons, My altimeter will show changes when my Kinsler gauge sites still.

Instead of agruing over the net over this, we should compare the 2 methods side by side when we meet in Atlanta.

 

[Dan_Cousin]

LLLLLLEEEEEEEETTTTSSSSSS get ready to RUMBLEEEEEE!!!!!!!!!!!!!!

 

[Rudy Formanek]

Kinsler also makes a air density gauge,sorry don't know how it compares on price. It used to be around $70.00, but I can't even remember how long ago that was. Seen alot of model boat racers with them on the Left Coast. Rudy

 

[JKramer]

Here is a chart from a Daqpod unit back last December

AIR DENSITY CHART

0.0765716

Date 25-Dec

Percent Time A/T R/H Bar/P DaqPod

101.31 3:23 42 56 29.34 0.077578

101.31 4:29 42 55 29.34 0.077573

101.82 5:11 40 59 29.37 0.077967

101.83 5:41 40 58 29.37 0.077975

101.83 5:46 40 56 29.37 0.077975

101.84 5:47 39 56 29.37 0.077978

102.05 5:51 39 55 29.37 0.07814

102.04 5:53 39 56 29.37 0.078137

99.29 5:56 52 66 29.37 0.076025

98.04 6:01 59 52 29.4 0.07507

97.67 6:04 61 47 29.4 0.074789

97.49 6:07 62 44 29.4 0.074653

97.12 6:11 64 41 29.4 0.074367

96.69 6:36 67 34 29.43 0.074038

I am attaching a file in Excel that shows the changing Air Density as the Air temperature, Relative Humidity and Barometric Pressure numbers change. I had the unit outside until around 6:00 and then moved it into the shop

With this you are checking all three, Air temp, humidity and barometric pressure. No guess work here!!!!

 

[Brad Christy]

Terry,

If I am guessing correctly, an "altimeter" uses air pressure to indicate altitude. How does it differentiate between a change in altitude and a change of barometric pressure? If you fly through a pressure front and the barometric pressure changes a significant amount, what is it about its sensors that tell it you didn't increase/decrease your altitude?

Just curious...........

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[Terry Keeley]

Terry,

If I am guessing correctly, an "altimeter" uses air pressure to indicate altitude. How does it differentiate between a change in altitude and a change of barometric pressure? If you fly through a pressure front and the barometric pressure changes a significant amount, what is it about its sensors that tell it you didn't increase/decrease your altitude?

Just curious...........

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Hey Brad, it's a sensitive barometer, that's all. The needle is calibrated to read 1000' for every inch of mercury change in air pressure, that's the "standard". When you go from say sea level to somewhere that's 1000' asl it'll read 1000' feet if the air pressure is the standard 29.92" Hg (14.7psi).

Pilots set the actual air pressure given by air traffic control in a little window that compensates for variation from standard, so it reads correctly. But, if you leave the window set at 29.92" it'll read what's called a "pressure altitude" and will basically give an altitude related to standard pressure, so it compensates for change in elevation and changes in air pressure at the same time, just like a barometer. Totally confused now? :blink:

Now you can tell me how to cut an arched exhaust port on a 10 degree upward angle w/o CNC. :lol:

I actually think I've got that one figured out, scarry. h34r:

Here is a chart from a Daqpod unit back last December

AIR DENSITY CHART

0.0765716

Date 25-Dec

Percent Time A/T R/H Bar/P DaqPod

101.31 3:23 42 56 29.34 0.077578

101.31 4:29 42 55 29.34 0.077573

101.82 5:11 40 59 29.37 0.077967

101.83 5:41 40 58 29.37 0.077975

101.83 5:46 40 56 29.37 0.077975

101.84 5:47 39 56 29.37 0.077978

102.05 5:51 39 55 29.37 0.07814

102.04 5:53 39 56 29.37 0.078137

99.29 5:56 52 66 29.37 0.076025

98.04 6:01 59 52 29.4 0.07507

97.67 6:04 61 47 29.4 0.074789

97.49 6:07 62 44 29.4 0.074653

97.12 6:11 64 41 29.4 0.074367

96.69 6:36 67 34 29.43 0.074038

I am attaching a file in Excel that shows the changing Air Density as the Air temperature, Relative Humidity and Barometric Pressure numbers change. I had the unit outside until around 6:00 and then moved it into the shop

With this you are checking all three, Air temp, humidity and barometric pressure. No guess work here!!!!

Cool stuff Joe, any idea how it measures humidity?

 

[Don Ferrette]

Terry-

Ok let me get this straight, you saying set the altimeter to 29.92"hg as a benchmark just like we typically use 40 as a benchmark Magnehelic setting on a flowmeter. You then watch for changes on the altimeter, not actual reading since unless you know the exact barometric pressure for where you're at the exact moment you set it you are not reading actual correct data. Is this right? :huh:

Joe (Knesek)-

How about posting a link for a pic of your altimeter. Just for grins I checked Ebay & Yahoo auction site & the cheapest used altimeters that ain't 30 years & look like you might trust them after you had them checked out were $150 and up. The cheapest one was at $100, 2 days left & a BIG disclaimer to have it calibrated before you used it. :blink:

So where is the savings you speak of? I guess we need to send some cases of beer up to Terry & see if he could do some more "trading" .

Also found a nice looking Tanner density guage at Racing Parts Warehouse for $99.95

http://store.racerspartswarehouse.com/tan81020.html

 

[Terry Keeley]

Terry-

Ok let me get this straight, you saying set the altimeter to 29.92"hg as a benchmark just like we typically use 40 as a benchmark Magnehelic setting on a flowmeter. You then watch for changes on the altimeter, not actual reading since unless you the exact barometric pressure for where you're at the exact moment you set it you are not reading actual correct data. Is this right? :huh:

Ya, think you got it. For instance, if you're in New Orleans at sea level it'll read sea level if the air pressure is standard or 29.92". To account for changes in air pressure you just leave the setting window at 29.92" and it will show below sea level if the air pressure is high (making the density high) and above if the pressure is low, like when weather is coming.

In Denver it'll read 5000' on a "standard" day or plus or minus for variations in air pressure.

A barometer does the same, at sea level on a standard day it'll read 29.92", at Atlanta on a standard day it'll read 28.92" (1"Hg = 1000'), Denver will be around 24.92...

BTW 100% air is 29.92" Hg and 15 deg C (59F) and goes down about 1% for every 60' of pressure altitude (0.06"Hg) or 3 degrees C (5F).

I've seen a high of 104% here, that was 250' (29.67"Hg) and 4C, the hard part is burning the fuel when there's ice forming around the pond. :blink:

 

[JKramer]

Terry, it has its own Honeywell sensor +_ 2 % accuracy from -40 to 185-F Range from 0% to 99%.

 

[Don Ferrette]

This is cool. Not cheap, but boy it sure is compact & easy to read-

http://www.microtim.com/

My trusty density guage has been 'ol faithful for over 7 years but those easy to read digital numbers..... hmmmm. B)

Anyone got any experience with one? Do you need the static port ($20 more) option? :unsure:

 

[DaveMarles]

U'all muss be more teknickul than me so's I only use one of them RAD meters. ( or got too much time on your hands)

I got mine from Speedway in the USA phone 420 474 4411. Its the same meter as the Kinsler but about 40 bucks cheaper. B)

 

[Preston_Hall]

Save your money and invest in 3rd channel needle setups.

 

[Joe_Knesek]

This is cool. Not cheap, but boy it sure is compact & easy to read-http://www.microtim.com/

My trusty density guage has been 'ol faithful for over 7 years but those easy to read digital numbers..... hmmmm. B)

Anyone got any experience with one? Do you need the static port ($20 more) option? :unsure:

I'll let you know Don when I get mine in. It's what I'm using with my new flow meter. As for your request regarding my altimeter, I have a photo of it in my gallary.

 

[JKramer]

I know this is a little off topic but I run RC Drag cars and a third needle is of no need for us guys. You have to be on the first time because there is no second time, as the big boys say, "your on the trailer". We have 21's that cover the 132 feet(1/10 of a quarter mile) in the 1.5 second bracket and MPH range of mid 90's. The best turned so far is 98 MPH but could not back it up.

 

[Don Ferrette]

I know this is a little off topic but I run RC Drag cars and a third needle is of no need for us guys. You have to be on the first time because there is no second time, as the big boys say, "your on the trailer". We have 21's that cover the 132 feet(1/10 of a quarter mile) in the 1.5 second bracket and MPH range of mid 90's. The best turned so far is 98 MPH but could not back it up.

Cool. B) So Joe, are you gonna be the first to crack 100?

 

[JKramer]

Don, not to miss lead you but I did not turn them times. I will be going to that class next year. I do hold the national Funny Car record.