Digital Manometer- Uses? Tips/tricks? Never touched one

[Itsjustdirt]

Never had our touched a digital (or manual) manometer before. Few questions...

1. Is a $30 generic one ok if its not a tool I use frequently?

2. WTF can they be used for? Any use in homeowner AC work? How do you use it to tell if you have a gas line leak like others have mentioned? Can it tell if I have negative or positive pressure in my house? Can it be used to tune a positive pressure fan to get "just a little" positive pressure or am I WAYYYYYYYYY OFF with its uses? Tips/tricks?


I'm clueless...be nice (or be really mean but teach me something, please).

 

[texasprd]

...WTF can they be used for?...

You can use it for testing blow-by on a Dodge Cummins 12-valve - likely on other engines as well, if you know what the specs are.

 

[Itsjustdirt]

interesting....

 

[Milton Shaw]

Manometers are used to check extremely low air/gas pressures and differences in air pressures. Most mechanical gauges don't really read and work much below 5 psi. Manometers work in inches of water pressure. For instance approx 400 in water pressure is about 15 psi. You use a manometer to check and set gas pressure on stoves, furnaces, etc. You can also use them to check back pressure on tuning air ducts and checking for pressure drop on filters and whether or not filters are clogged. On vehicles the pressures and too much for most manometers to read or be much use on. As one other mentioned crankcase blow by or PCV valve operation would be a low enough pressure to use them on. On gas systems for instance NG needs about 7 inches of water pressure before the valve and is reduced to about 4 inches at the burner. Propane burns at about 10 inches after the regulator. No way to test these low pressures easily without a manometer.

 

[bonneyman]

I once had an instructor who claimed all he needed was a gauge set and a magnehelic (fancy old school manometer) to troubleshoot any A/C system.

While I never got to that level of proficiency I know manometers can be really helpful. I'd stick with Dwyer products. They've been making quality measuring instruments for over 80 years.

http://www.dwyer-inst.com/Product/Pressure/Manometers/

 

[danski0224]

For measuring typical positive or negative pressure in a building, you will need a micro manometer and a blower door.

Measurement scale is Pascals. Small.

 

[royesses]

At Caterpillar we used Dwyer H2o manometers to check exhaust back pressure. Also use it for adjusting gas pressure on natural gas valves.

Roy

 

[timgunn1962]

If you need one, you will already know. As you asked the question, it's a pretty safe bet you don't need one.

For measuring low pressures, there's not much to beat a U-tube manometer. One can be cobbled together very easily from a length of clear flexible tubing and coloured water. For lower ranges, an inclined U-tube can be used.

I use digital manometers because I need to use them in the field and they are easier than faffing about with a u-tube. I check the digital against a U-tube regularly and use a U-tube whenever I need to be certain of a low-pressure measurement in the shop.

I like the Dwyer 1227, which is a dual-range (vertical and inclined) U-tube.

The big advantage of a U-tube is that there are only 2 things, apart from the pressure being measured, that can affect the reading. One is the density of the fluid (so you make sure you use the right stuff) and the other is Gravity, which we can reasonably assume to be constant: If Gravity fails, you'll have much bigger problems than inaccurate pressure readings to contend with.

 

[67CarGuy]

The above explanations are pretty satisfactory... what are you expecting or trying to measure? I use one as an energy/building analyst, with a blower door or duct blaster to measure air leakage. Most homeowners don't need one, as the good ones are prohibitively expensive unless you're earning your living from it.