In below picture, is ammeter AC or DC? Is there direction for connection with load in series? If so what if I connect in wrong direction?
It's a moving iron meter hence this symbol: -
Taken from here
Moving iron meters are used for DC AND AC so, the meter needle will only move in a clockwise direction irrespective of current polarity. If it used a magnet it would be polarized and with AC, the needle would barely move (because the needle would try and move clockwise and counter-clockwise at the AC frequency).
It's also worth noting that the symbol that looks like an upside-down "T" next to the moving iron symbol also has a meaning as does the 5 sided star with a 2 inside: -
Extra picture from here.
There are three clues:
- The scale isn't linear so that implies that it is a moving iron meter.
- The ≂ symbol indicates that it can handle DC and AC. (The '-' indicates DC and the '~' AC.
- The terminals are not labelled. If polarity mattered they would be.
The meter can be wired either way.
The moving iron works on the principle that the iron place near the magnet attracts towards it. The force of attraction depends on the strength of the magnetic field and not on its polarity.
See the linked article for a list of advantages and disadvantages of moving-coil meters. They are favoured on cheap electrical devices such as 12 V battery chargers, etc., where they can be considered as a current indicator. Calibration in many cases is going to be terrible.
The symbol, circled in red, indicates it's an AC/DC meter.
