practical advice on differential pressure gauge selection? 1

[amazing azza]

Hi guys, trying to select a pair of diff pressure gauges to monitor

- supply pressure at AHU fan, and
- static pressure inside a clean room

I am looking through the Dwyer offerings and even after eliminating the obvious misfits there are still too many choices and the difference between them is not always clear.

Any advice in picking one over the others? Are there any particularly popular models?

 

[Compositepro]

Well, we are as clueless as you are because you have not told us much. Call Dwyer and you can play 20 questions with them instead of us.

 

[MintJulep]

trying to select a pair of diff pressure gauges to monitor

But you linked us to a transmitter page.

Which do you want?

 

[amazing azza]

Call Dwyer and you can play 20 questions with them instead of us.

Someone is having a case of the mondays

But you linked us to a transmitter page.

Gauges are people transmitters too

 

[Compositepro]

Gauges are not transmitters. You are now starting to ruin our Tuesday as well.

 

[amazing azza]

Gauges are not transmitters. You are now starting to ruin our Tuesday as well.

u mad bro?

 

[MintJulep]

No, seriously pressure gauges and pressure transmitters are different things.

That's why they have different names.

That's why Dwyer has different pages for them.

Picking advice step 1: Identify your need.

 

[danw2]

A gauge is an indicator. A transmitter creates an electrical signal. Gagues can have options that include an electrical transmitter or switch(es).

For either gauge, transmitter or switch, you need to know the pressure range needed because that limits selection. Room-to-room differential might be as low as 0.1"wc full scale. Fan ? Accuracy falls off on the low end (as does resolution) so a 5" span is not a good fit for something like that.

For these kinds of ranges an empirical test method is a water manometer- a length of transparent tygon tubing partially filled with water held to form a U shape and a tape measure to measure the difference in levels.

Who is going to stand and read a fan supply pressure? Isn't a signal needed for automation/control? Is there even a need local indication for fan suction pressure?

Are the display engineering units OK (in wc)?

How does it mount? door panel? subpanel/wall?

Are the hose/tube barbs positioned well for installation?

What accuracy (comparison to national standard) is required?

Is internal damping needed, if so, available? Low pressures can be too 'jumpy' as the lab gals say.

If you do need a signal out, is it 2 wire 4-20mA or a 4 wire signal? Is the output isolated ? Can the zero be tweaked?

Are there exposed screwdriver/tweaker adjustments (zero, alarm SP, display brightness) that gremlins will play with? Is that good or bad?

Can the units be calibrated by a 3rd party? Both Input/pressure side and signal side? (Low range sometimes need to be calibrated by the manufacturer.)

Is the cost of re-calibration a fraction, equal to or greater than replacement cost?

Does the unit use anything quirky like a fob (or HART) for any operations or commissioning/cal purposes? Is the end user high functioning enough to deal with a fob? Are you?

Is the final product replaceable out-of-the-box with a new unit or does a new unit require technician level commissioning? Is your intention to build a continuing service base or not?

Is the room wash down? Does the so-called NEMA 4 rating (like the bezel gasket) really look robust enough to hold up to the cleaning crew, the hose and the chemicals they use? Does the DP really have to be in washdown area or can just the pressure tap be there?

Is the unit robust enough to be removed from service (tube fittings wiring, mounting) multiple times for non-in-situ calibration and survive? Is the wiring plug-removeable or screwdriver-wires-dangle?
Relatively delicate measurements have been done in the past by some relatively delicate instruments. That's fine, so long as the working environment is equally delicate.

Does it come with a cal cert? Std or optional? Traceable to? Does the cal cert meet end user's requirements or will you have to have it cal'd to get a suitable cal cert?

 

[Compositepro]

Okay, let's make that a game of 27+ questions.

 

[amazing azza]

danw2, thank you so much for a meaningful reply!