Pressuretrol & internal syphon gauge-is it true?

Steve_168

Is it true that these two devices can be out of sync?
Meaning if the pressure gauge on my Single Pipe gas fired boiler is reading 1.5psi the pressuretrol may have a different reading? Per the tech, the two units are in different spots of boilers (adjacent to one another) it is possible to have a slightly different reading.
Unit is not cutting off at pressuretrol limit and the pig tails are cleaned. But the unit does turn back on at cut in psi, set at .5 psi. any ideas?

Last question, as i understand it, water hammer is loud. If i have noise that sounds like a silver dollar rolling around in my pipes, is that consider water hammer?

Thanks in advance.