SPG and DIVE watch disagree

[2New2Scuba]

Should i adjust the SPG with the screw on the face to match the watch (Shearwater Peregrine)? SPG shows about 200 psi more.

 

[fred32176]

A peregrine is not air integrated. Can't tell you the pressure in a tank.

 

[Dan]

Should i adjust the SPG with the screw on the face to match the watch (Shearwater Peregrine)? SPG shows about 200 psi more.

I have never seen a screw adjustable SPG and Peregrine with AI. May be you can post some pictures of what you are talking about?

 

[2New2Scuba]

I have never seen a screw adjustable SPG and Peregrine with AI. May be you can post some pictures of what you are talking about?

They're both at the dive shop now. It's Perdix AI with transmitter.

 

[Dan]

That looks like an analog SPG. I don’t think you can adjust it.

The gauge that has screw on the face at the center is not SPG. It’s a depth gauge. The screw is only for resetting the max depth dial to zero after a dive.

I’d trust your Perdix and use your SPG as a back up. 200 psi off (on the low / safe side, I hope) out of 3000 psi is about 6.7%. Not much to worry about. The actual tank pressure would be more than what your SPG would show.

My old SPG had similar lower display. I just replace it with a new one since it only costs $75.

My old SPG (no screw adjustment)

 

[2New2Scuba]

Thank you. I found a similar post in the list before- differed by 150 psi. In my case the watch is 150ish psi lower than the SPG. Be nice to match but I'll rely on the watch with the SPG as backup if watch breaks (glass on rock, stolen etc but build that lower 7% to the SPG reading...unless someone has better advice.

 

[Dan]

What is more likely to happen is your pressure transmitter runs out of battery charge during a dive.

You can conserve the transmitter’s battery by only turning on the tank valve right before water entry (verify the tank pressure with your Perdix and SPG) and turn the valve off after the dive and purge the air pressure off your regulator.

If you see any pressure in your SPG, the pressure transmitter will be ON and transmitting the digital pressure signal to your Perdix. If that happens when you are not diving, you are wasting the pressure transmitter battery.

My Teric’s pressure transmitter battery lasted over 2 years / 500 dives by only turning the tank valve on right before water entry and turning the valve off right after the dive. I only replaced it when the Teric failed to display the pressure right before water entry (which I ended up using my SPG for the dive). After the dive I replaced the transmitter battery, but the Teric was still not showing the pressure until I put the Teric right on top of the transmitter, which means the Teric antenna is broken, not the transmitter battery running out of juice.

I sent the Teric to Dive-Tronix for evaluation. They confirmed that my Teric had a broken antenna.

 

[2New2Scuba]

What is more likely to happen is your pressure transmitter runs out of battery charge during a dive.

You can conserve the transmitter’s battery by only turning on the tank valve right before water entry (verify the tank pressure with your Perdix and SPG) and turn the valve off after the dive and purge the air pressure off your regulator.

If you see any pressure in your SPG, the pressure transmitter will be ON and transmitting the digital pressure signal to your Perdix. If that happens when you are not diving, you are wasting the pressure transmitter battery.

My Teric’s pressure transmitter battery lasted over 2 years / 500 dives by only turning the tank valve on right before water entry and turning the valve off right after the dive. I only replaced it when the Teric failed to display the pressure right before water entry (which I ended up using my SPG for the dive). After the dive I replaced the transmitter battery, but the Teric was still not showing the pressure until I put the Teric right on top of the transmitter, which means the Teric antenna is broken, not the transmitter battery running out of juice.

I sent the Teric to Dive-Tronix for evaluation. They confirmed that my Teric had a broken antenna.

Very helpful.
Did you see the discrepancy between the two readings?

 

[Rilelen]

My SPG consistently reads 200psi higher than my transmitter; I'm not sure which is correct, so use the lower reading. Been meaning to check both against other gauges.

Interestingly enough, I ran a tank down to nearly empty the other day (on purpose), and the SPG & transmitter both converged at the very end. The transmitter was actually reading slightly more air at that point (88psi) than the SPG (which was at 0).

 

[Dan]

Very helpful.
Did you see the discrepancy between the two readings?

My new SPG reads 100 psi lower than my Teric AI. The gap gets smaller at lower pressure. At half tank it’s only 50 psi. The % error is constant though out the pressure range, 3,3%.