Magnahelic Gauge - which port to plug

[TheScubaPanda]

I bought an old magnahelic Gauge on eBay 0-3 in of water. And try to set it up.

There's 2 ports: 1x LP and 1x HP.

I guess the LP is the one I need to use to measure the cracking pressure.

Now : shall I plug the HP inlet?
I found that plugging it with my finger consirably change the result.

Thanks

 

[rsingler]

Magnehelic Setup

 

[TheScubaPanda]

So if I read correctly. I shouldn't plug the HP port.

Thanks mate