Circuit symbol for ammeter with output
We don't normally call that an ammeter, but a current-controlled voltage source. One common symbol is this (courtesy of Wikimedia):



Text next to the symbol should indicate how it's controlled. For example, "\$I_1\times{}10\Omega\$".

If you want to represent a physical device that has this function, you'd probably just use a rectangular box with pins corresponding to each of the physical pins.