does it need to be connected to the first stage directly or can i also put it on a hose?
Has to be on the 1st stage
I don't know. I attached mine onto the first stage. It screws into one of the threaded attachment points. I think putting it on a hose would defeat the purpose.....to keep your pony/bail out bottle set-up compact and streamlined as possible. Another dangling hose is not what I wanted on my set-up. If you want to use a hose and this fits your set-up, I'd just go with a pressure gauge that is a little bigger/easier to see. Hope this is helpful.
This pressure gauge is great for direct connection to a high pressure port of a regulator first stage. I have an air integrated computer on my primary regulator rig & use this gauge as a backup in case of computer failure. To answer your question, it COULD be connected via a high pressure hose, if desired, but if that's the intended configuration I'd use a slightly larger & more finely tuned mini pressure gauge.
I connected it to my first stage directly, however, I don't know why you could not mount it to a hose first, you would just need to make sure you have the right fittings.
I don't see any reason why it would not work on a hose, if you can find a hose with the proper connections, but it is not really designed to be used that way, and I have not done it, so I can't answer from experience. They make pony bottle gauges with short hoses, so those would be a better choice, I would think.
Theoretically, this could be mounted on a hose... However this is really not advisable. Others I have dove with have had the glass on the face of this type of gauge shatter when bumped and crushed against other objects, so mounting it in a less protected area might reduce the life of it.
I have mine connected on my pony bottle first stage. With the proper hose connector fitting I don't see why it couldn't be connected to a high pressure hose and port. If it is to be your primary gauge I'd invest in an OMS or similar pressure gauge.
No, you need a Mini-SPG to HP Hose adaptor to accomplsih that. I am not sure if LP has those, but Dive Gear Express does...