I have a three point mounted Fimco sprayer with a roller pump. The gauges that I have bought has the needle bounce up and down and no way to actual read it. Need help from some experts.
Mine does it too, I think that's just inherent in the design with the pressure regulator or relief valve. A bladder accumulator of some sort may help a little.
Get an oil filled gauge. The oil dampens the movement of the brass (gauge) pressure chamber. Any application where non-steady pressures are involved do best with that type gauge. Also, selecting a gauge that will work in the mid position rather than full scale deflection will be the most reliable.