The ohmmeter and the high resistance meter are basically the same thing, both are used to measure the resistance value up to megohm, of course, the zd high resistance meter may be higher, such as tens of hundreds of internal mega.
There is a device for generating high voltage in the insulation resistance meter, such as a shaking meter, which generates high voltage, which means that it may produce a breakdown effect during measurement, while the other two types will not. Therefore, the insulation resistance meter can measure the insulation capacity under a certain voltage, that is to say it can measure the withstand voltage and the insulation resistance under a certain voltage.