Inexpensive high pressure gauge head w/ bumper?

[n8n]

Hi all,

Just bought myself a new "toy" (which really isn't, as I needed it) - a Viair 450P 12V compressor. It's so much nicer (albeit much heavier!) than the HF cheapie it's replacing, but it's the real deal.

One niggle: the Viair supplied pressure gauge is wildly inaccurate, it reads 4 PSI high at 36 PSI vs. my Longacre gauge.

My immediate thought is to replace it with another Longacre head, but the highest pressure reading one they sell is 60 PSI and this compressor is capable of 150 PSI. I don't really have any need to inflate anything *now* that would go over 46 PSI I think? (rear tires on my car) but I just don't like installing a gauge head that could conceivably bump the needle off the stop in normal operation.

Thanks for any advice!

 

[jeejay]

How do you know the Longacre gauge is more accurate by comparison?

 

[n8n]

I have several other gauges and a Longacre inflator, they all agree within 1 PSI

 

[larry_g]

Hi all,

Just bought myself a new "toy" (which really isn't, as I needed it) - a Viair 450P 12V compressor. It's so much nicer (albeit much heavier!) than the HF cheapie it's replacing, but it's the real deal.

One niggle: the Viair supplied pressure gauge is wildly inaccurate, it reads 4 PSI high at 36 PSI vs. my Longacre gauge.

My immediate thought is to replace it with another Longacre head, but the highest pressure reading one they sell is 60 PSI and this compressor is capable of 150 PSI. I don't really have any need to inflate anything *now* that would go over 46 PSI I think? (rear tires on my car) but I just don't like installing a gauge head that could conceivably bump the needle off the stop in normal operation.

Thanks for any advice!

This supplied gauge that is so wildly inaccurate, where is it located?

Is this gauge the one on the pressure tank or is it a separate gauge that you measure tire pressure with?

If it is the one on the pressure tank then can you describe your testing procedure?

How are you connecting the two gauges to the same pressure source at the same time?

On edit; the following is from the manual;

INLINE PRESSURE GAUGE:
1. The pressure gauge on the inflation gun provides convenient tire pressure monitoring when airing
up or down (not airflow of the compressor). This eliminates switching back and forth between a
tire chuck and a tire pressure gauge.
2. Please note that during inflation and deflation, due to air velocity, pressure gauge cannot provide
accurate pressure readings. Release lever on the tire inflation gun during inflation to check
tire air pressure.

Are you following this procedure?


Dwyer makes good gauges and this link will take you to some 1.5% gauges. http://www.dwyer-inst.com/Product/Pressure/SinglePressure/Gages-Dial/SeriesUGK

You do realize that a 1.5% gauge could read up to 3 psi off on a 200 psi gauge and still be 'accurate'. The gauge on your inflator is probably a 3 to 5% gauge and well within specs.

by "bumper" do you mean "snubber" ?

lg
no neat sig line

 

[jeejay]

The other thing about analog gauges is that they should have double the pressure capacity you're checking for best accuracy. So if you're comparing two with different scales, that could be a problem also.

 

[larry_g]

The other thing about analog gauges is that they should have double the pressure capacity you're checking for best accuracy. So if you're comparing two with different scales, that could be a problem also.

I concur. Another way to say this is your desired pressure reading should be at ~50% of full scale Readings near each end of the scale tend to be less accurate. I believe the OP is working with a 200 psi gauge.

lg
no neat sig line

 

[rshadd]

I've always found Ashcroft's pressure gauges to be spot on.

 

[n8n]

This supplied gauge that is so wildly inaccurate, where is it located?

Is this gauge the one on the pressure tank or is it a separate gauge that you measure tire pressure with?

If it is the one on the pressure tank then can you describe your testing procedure?

How are you connecting the two gauges to the same pressure source at the same time?

On edit; the following is from the manual;



Are you following this procedure?


Dwyer makes good gauges and this link will take you to some 1.5% gauges. http://www.dwyer-inst.com/Product/Pressure/SinglePressure/Gages-Dial/SeriesUGK

You do realize that a 1.5% gauge could read up to 3 psi off on a 200 psi gauge and still be 'accurate'. The gauge on your inflator is probably a 3 to 5% gauge and well within specs.

by "bumper" do you mean "snubber" ?

lg
no neat sig line

The gauge is on the inflator gun that was included with the compressor. There is no tank, it's an "automatic" compressor meaning it shuts off when no air is flowing. you basically squeeze the trigger to inflate, release to check pressure (so the gauge is connected to the chuck but not the hose.)

And yes, I do understand the percentage thing, but when my eyeball can see the needle clearly over the 40 PSI line but when I check with my 60 PSI Longacre gauge, which I trust to be accurate, it reads 36 PSI, that's a problem.

Or am I being overly picky and should just accept that if I want my tires inflated more accurately that I'll have to carry a separate gauge?

 

[larry_g]

And yes, I do understand the percentage thing, but when my eyeball can see the needle clearly over the 40 PSI line but when I check with my 60 PSI Longacre gauge, which I trust to be accurate, it reads 36 PSI, that's a problem.

Or am I being overly picky and should just accept that if I want my tires inflated more accurately that I'll have to carry a separate gauge?

If you want your tires inflated to a known pressure then your going to have to get a calibrated gauge. You have two unknown gauges, one which you "trust" but probably have never calibrated and one that you don't "trust". I spent to many years with instruments to trust any of them.

If your going to be picky then your going to have to pay up and get calibrations done and done on a regular schedule. I linked you to some good gauges, did you look at them? If you read and study a few catalogs you'll find most gauges are not that accurate, and if you want accuracy your going to spend some money.

Confucius said, "Man with two watches never know what time it is".

Good luck on your quest.

lg
no neat sig line