self made balometer

[eskimo2]

alnor and testo to name a couple have micro-manometers.
these can measure velocity in the duct etc etc
they are programable to measure duct size and hence volume......

now my question

has any one made their own "flow hood" using these?

alnor has one (a kit) that seems to include the matrix which is used in the TSI and Alnor flowhoods

any thoughts

[Steve Wright]

We have made devices to capture air from odd teminal devices so we could measure airflow, however I don't think anything will duplicate accuracy like a certified flow hood.

[TRASH101]

Hello Eskimo2

You can lash a balometer/ hood together but consider these issues before you do.

1) how are you going to calibrate it.

(different hoods at different air volumes can produce different resistance characteristics)

2) Anyone involved in validation/commissionig should be asking what instrument you used and prove it is calibrated.

3) Homemade hoods tend to be heavy and cumbersome.

4) You need a REASONABLE seal around the diffuser/grille

5) Use a flow grid if possible, which should cover a high percentage of the hood apeture you intend to measure from. ( avoid using single point equipment i.e. pitot, hot wire and avoid small diameter anemometers). The whole idea is to measure as much of the volume at the apeture as possible in an instant.

If you still think it is worth building one then before using it in anger cross reference at regular intervals to a known reading from a calibrated industry approved meter and still be prepared to have your figures thrown back at you.

It can get pretty nasty when consultants and commissioning engineers start getting bitchy about their equipment.

[eskimo2]

Steve,
Your right of course...but what did we use before them...the flowrite? with self made cone

[eskimo2]

Trash 101
if you check the alnor site they have a micrometer which also has a matrix (same thing at the bottom of the alnor flowhood)......i was wondering that if one used the matrix with a cone/hood with the dimensions programmed into the micrometer then why wouldnt it be right?

i can make a cone/hood and buy the kit cheaper that what they sell a complete flow hood?...or at least thats my reasoning....I'm guessing its the same instrument/meter and wonder why it wouldnt it work if fitted to a different hood?

As i wont be doing work for consultants it wouldnt matter...and besides commissioning guys have been known to record doggy figures for perusal by consultants...i was taught by the best of them.....when in desparate of course

[TRASH101]

if you check the alnor site they have a micrometer which also has a matrix (same thing at the bottom of the alnor flowhood)......i was wondering that if one used the matrix with a cone/hood with the dimensions programmed into the micrometer then why wouldnt it be right?

i can make a cone/hood and buy the kit cheaper that what they sell a complete flow hood?...or at least thats my reasoning....I'm guessing its the same instrument/meter and wonder why it wouldnt it work if fitted to a different hood?


Yes Eskimo it would work although you will still have to "tune" your results to the specific hood and may alter as much as 20% from measured to actual and then its different again for "reversed flow" so cross calibration is still required (as you are buying a micromanometer then an average of multiple pitot readings for various flow rates will put you in the right ball park)


and besides commissioning guys have been known to record doggy figures for perusal by consultants

I couldn't disagree more;)