Portable pump or floor pump to maintain tire pressure

I’m using Birzman mini pump which can realistically pump up to 85psi of the recommended pressure for my tyres and checking the pressure by using a Digital pressure gauge.
Earlier tried the floor pump but cannot sustain the required pressure of 85 psi although it showed in the built in pressure gauge at 85psi reading, when I counter check it with the digital pressure gauge, the margin of error is so huge.