Schematic diagram of the structure of a clamp ammeter
Clamp ammeters are divided into AC clamp ammeters and AC and DC dual-purpose clamp ammeters according to different structural principles. If the measuring mechanism in the clamp ammeter uses a rectifying magnetoelectric instrument, it can only be used to measure alternating current. If the electromagnetic system measurement mechanism is used, it can be used for both AC and DC. The clamp ammeter is essentially composed of a rectifier meter (AC type) or an electromagnetic meter (AC-DC dual-purpose type) plus a current transformer, and its structure is shown in Figure 3-11. The iron core of the current transformer has a movable part, which is connected with the handle. When using it, first press the handle to open the movable iron core, put the wire to be measured into the jaw, and then release the handle to close the iron core.
At this time, the wire passing the current is equivalent to the primary winding of the transformer, and the coil wound on the core is equivalent to the secondary winding of the current transformer. The rectifying or electromagnetic ammeter is connected to both ends of the secondary winding. When the secondary winding induces current, the indicated current is the induced current in the secondary winding, and its magnitude is proportional to the working current in the tested wire. So as long as the calculated scale is used as the scale of the ammeter, when the ammeter pointer deflects in proportion, it can indicate the value of the measured wire current.
