The ordinary ampermeter shows mean square value of current. The oscillograph will help to define its amplitude value. For this purpose it is necessary to add the special powerful low-impedance resistor to it — the shunt.
Instruction
1. Make sure that the chain in which it is necessary to define amplitude value of current has no galvanic contact with the power supply network. If such communication is available, the way of measurement described further cannot be used.
2. Cut off power a chain, turn on in its gap the shunt with such resistance that its influence on current was minimum (if the chain consists of several consistently connected parts, choose the place of its gap as it is possible closer to a point with a zero potential).
3. Parallel to the shunt connect the electron beam oscillograph switched to an operating mode with an open entrance. Do not connect the case of an oscillograph to anything and not to receive electric shock because of potential difference between the general wires of an oscillograph and the test device, work in rubber gloves.
4. Until the chain is switched off, the handle of movement of a beam down precisely combine a horizontal line on the oscillograph screen with the zero line of a slip with a grid.
5. Include current in chains then adjustment of strengthening of an oscillograph achieve that the amplitude value of tension was located on the screen on height. Count and write down the number of divisions on the screen (rather zero line) corresponding to this value.
6. Cut off power a chain. Disconnect the shunt from the checked chain, but not from an oscillograph, and in the checked chain restore connection. Turn on the shunt in a rupture of other chain consisting of the loading consuming approximately the same current, the ampermeter of a direct current and a source of adjustable constant tension.
7. Regulating a source, achieve that the line on the screen deviated the zero line of a grid on the same number of divisions. Read indications of the ampermeter — they will correspond to current amplitude during the previous measurement.