Help! How Is Anyone Supposed To 'accurately" Read An Air Pressure Gauge Like This One?

The pic of my gauge on page 1 is the same dual setup. Two needless on one gauge. Mine has a white needle for primary and blue needle for secondary. His had an orange primary and as green secondary.

This is going to sound like a dumb question, but this is the first time I have seen primary and secondary air on the same gauge. How does one determine whether it's showing the reading for the primary or secondary?

This is going to sound like a dumb question, but this is the first time I have seen primary and secondary air on the same gauge. How does one determine whether it's showing the reading for the primary or secondary?

On my 2019 Freightliner primary and secondary are on the same gauge with 2 needles, a white one for primary and underneath it is a blue for secondary. Same for fuel and DEF white is fuel and blue is DEF

Oh man......that's some unfortunate math right there! No wonder you're unhappy about this gauge.

Thanks for trying.......but no cigar

I know. Anyway I should have said 1/2 way between 90 psi and 120 psi is 105 psi.

And yes; No Cigar!

I did ask my instructors about it. As has been said here, the reading of the gauge is important and close enough (IOW, will not have to be absolutely 'exact') in all likelihood will be close enough to pass a DMV test.

Also, as has been said here, and adamantly emphasized and insisted by my instructors, the correct psi ranges for each test must be verbalized to the DMV tester.

As I study the photo of the gauge I notice that one needle width is about 1 psi.

Increments of 30 can be evenly divided by 6 to find where the the 5 psi increments are.

There are red and blue segments that are separated by a black line centered between the numbers on the gauge. The black line is the 3rd 5 psi increment between the numbers (15 psi above and below the numbers).

The center of each red or blue segment would be about 7 1/2 psi (which is what made it more confusing to me).

For the DMV test, if the needle is right at center of a red or a blue segment, I will say whatever even number it would be; example: 117 psi for (saying) needles have settled @ (117 psi) when preforming the Air Compressor Governor Cut-In Test if the needle on gauge is center of the 'higher' psi segment between 120 and 90. I will not bother saying 117 1/2 psi.

I am am sure I have it correct enough for DMV test now.

Thanks to everyone for your input.

Re what I just said:

For the DMV test, if the needle is right at center of a red or a blue segment, I will say whatever even number it would be;

OK, I know, I made a 'technical' error; I should have said:

For the DMV test, if the needle is right at center of a red or a blue segment, I will say whatever whole number it would be;...

OK I got it wrong again! Center of blue segments between 90 and 120; center of first segment (above 90) is 97 1/2 psi second segment center between the black line and 120 is 112 1/2 psi. etc.... ...I think anyway

I am not going to post here again until I pass all my DMV tests scheduled for next week and am waiting for CDL to come in the mail.

I am going to focus on all what I need to to pass the DMV tests for my CDL.

To all who undoubtedly have said something of my error/s, thanks even though I have not read any more posts and will not be answering them directly at this point in time because I will be taking a break from most computer things for the next week so I can do what I must in order to pass DMV Pre-Trip, Air Brakes, Skills, and Driving tests the first time.

Thanks everyone for your so very valuable input.

BTW, FWIW, I just want to pass the tests at DMV, I could care less about a 'Cigar'.

Hi all. I passed all the DMV tests!

The instructors were helpful. I was able to get it correct how to read the air pressure gauges.

I admit I was stressing a bit over it but I got over it and put my head into it.

Thanks to everyone that chimed-in.

Here is the photo of the same gauge that I added some lines and psi numbers to illustrate. I just did the best I could with the Microsoft paint program, did not use a micrometer so the lines are not 'exact' but as some have said here (thanks to those that did say) does not have to be dead-on exact. Close enough to the 'exact' reading and knowing the parameters for each particular test is what matters to pass. Also to be closer to 'exact', one pointer needle width at the tip of the needle is about 1 psi. I did when I read the gauge end up saying the reading is 104 psi because that is where it was pointing about 1 pointer needle width lower than right on the 105 psi line.

Hi all. I passed all the DMV tests!

This is all that matters. Congratulations. The next thing that matters is don't hit anything.