I'd like to buy an IP gauge; would like to understand differences between two types.

[Hatul]

I also bought the cheap one, #1. What bothers me is the zero is not floating like in the SPG but fixed against a post. I'm no expert on this but my understanding is the zero should be free and not be fixed.

Adam

 

[HenrikBP]

I have one of these that I picked up in perfect condition for $65.

Now that's just not fair ...

Henrik

 

[redacted]

I also bought the cheap one, #1. What bothers me is the zero is not floating like in the SPG but fixed against a post. I'm no expert on this but my understanding is the zero should be free and not be fixed.

Adam

Most of my SPGs have a stake at the zero. I found 2 out of over a dozen that float and they are 2 of the lower quality ones.

 

[Zung]

Most of my SPGs have a stake at the zero...

Same here. As long as it's OK-ish mid-scale, don't worry about the rest: it's only a Bourdon tube inside. Btw, the one shown also has a stop.

 

[Zung]

What you REALLY, REALLY need is a gauge with a mirror on the scale so you can line the needle up with its reflection to get it accurate within a needle-width and eliminate parallax error. Oh yeah--and the gauge needs to be calibrated to an example traceable to the National Bureau of Standards. That oughta set you back a few sheckels!!

NOOOOOOOO!
What you REALLY need is this.

"The Series DCG Digital Calibration Gage features a remarkable 0.05% full scale accuracy that includes the effects of linearity, hysteresis, repeatability, and temperature across the entire compensated temperature range. This gage was specifically designed to be a portable test gage where its unmatched accuracy is required. This is a highly durable gage that is housed in a rugged and compact 3 inch stainless steel case.
This highly accurate test gage offers menu configurable and password protected features that include engineering unit conversion, seven selectable languages, field calibration capabilities, as well as an adjustable bar graph and update/dampening rates.
Every unit includes an NIST Calibration Certificate."​

Currently on sale at $1186.75 only!

 

[herman]

If you are not using one of these,

Than you are not geting an accurate reading. Only $596.00 at Amron International.

Actually, the el cheapo one will be more accurate than this one....with it's bent needle from being used at 150% of scale.

For field use, accuracy is not really that important as long as it's repeatable (the same pressure reads the same all the time). The things you are looking for in the field are:

1. Is the IP the same as it was the last time. For service work we obviously want to know 135 psi really is 135 psi but for a field test as long as the IP measures the same each time, its exact value is not really important. What we do want to be sure of is it's not changing, either from dive to dive or increasing as we watch it. From a field test prespective, an unsteady/changing IP is the real indication of a problem, not the exact IP.

2. When just back from service, does it read the same as it did when it was sent out..if not why not. You should always check your regs when they are just back from service. The tech may well have changed the IP, no big deal in and of itself but you need to know it and if it changed a lot, why was it changed (it is possible it was not set properly).

3. Is the IP stable. This is the real thing the inexpensive gauge is good for. Acutal IP is no where near as important as it being stable. Reguardless of the accuracy of the gauge, it will almost certainly be consistant (ie off 10 psi every time) and will show creep (a slow increase in IP as the regs sets pressurized).

I own both, the inexpensive one that stays in my dive kit and a much better on that stays on the bench.