Hotwire ammeters are used for measuring :

• The hotwire ammeter is a device used to measure the intensity of alternating current or direct currents.
• It is based on the thermal expansion of a wire.
• Thermal expansion is proportional to the heat produced in the wire which is proportional to the square of direct current or the root mean square value of alternating current.

Therefore, we can say that hot wire ammeters are used to measure both alternating current and direct current.