I have wanted an easier way to judge tongue weight (i.e. no bathroom scale & lever), but didn't want to pay for a $140+ scale. I finally put together a "budget" version that should at least get me in the right ballpark when I have concerns using a small hydraulic ram & a pressure gauge.
I had looked at a few hydraulic rams, like those in a porta-power unit & ran across the Strongway hydraulic 2-ton mini ram sold at Northern tools (& Amazon). It is a small unit with a cylinder face area of 0.95 square inches (diameter = 1.10"). It is a bit under 6" tall & 1.5" across. I bought one for about $23 & also bought a 0-1000 PSI gauge with 1/4" threads for about $10.
I removed the hydraulic quick connect fitting from the ram (it was tight!), extended the cylinder & added hydraulic fluid. I got the bubbles out & set the cylinder at about 1/2 extension (1.5" ?) then attached the gauge in place of the fitting. I made sure that the hydraulic fluid was level with the top of the hole when I attached the gauge to avoid adding air. The gauge was tightened until it was face up with the ram upright. A quick test in the vice showed the gauge respond to pressure & return to zero when the pressure was removed.
The gauge readings are a little above the actual weight (5%) but good enough for my purposes. It was simple to use with a jack stand as support. Lowering the hitch with the trailer's screw jack until the jack foot was unloaded (off the ground) I was able to see the empty tongue weights of the small dump trailer (400 x .95 = 380 lb) & the 18' Aluma car hauler (150 x .95 = 142.5 lb).
These are the pieces used (pics are from amazon):