Signal power of irregular shape or high frequency cannot be measured by a wattmeter. Meanwhile, at adjustment of power amplifiers and transmitters it quite often is required. Indirect methods of measurement come to the rescue.
It is required to you
- - diodes;
- - K155AG1 one-vibrator or another;
- - resistors and condensers;
- - voltmeter;
- - probes;
- - soldering iron;
- - solder;
- - neutral gumboil.
Instruction
1. As loading for the power amplifier or the transmitter use the glow lamp. In the warmed status it should consume approximately the same power, as well as loading (respectively, a dynamic head or the antenna). Connect a lamp to an output of the device which signal power at the output you wish to measure, and then place it in an opaque tube that results of measurement were not affected by foreign lighting. If a tube metal, take the measures excluding short circuit.
2. From the opposite side place a photo cell of desirable type in the same tube. Connect it to the measuring device in the way which is the most suitable for this purpose. For example, connect the photoresistor or the phototransistor to the milliammeter via the power supply, and the photo diode - directly, without using such source.
3. Give a signal of the known amplitude on an input of the amplifier or transmitter. The lamp in a tube will begin to shine, lighting a photo cell, and the arrow of the measuring device will deviate. Remember its indications.
4. Now switch off the amplifier or the transmitter, disconnect from it a lamp then attach it to a constant voltage source via the ampermeter. Parallel to a lamp attach the voltmeter. Set such output voltage of the power supply that the device connected to a photo cell showed the same result, as in the previous case.
5. Now read indications of the voltmeter and the ampermeter, transfer them to the SI system then increase at each other. You receive the power consumed by a bulb at present. Just the same signal power was developed in the previous experience and by your amplifier or the transmitter.
6. If you have no photo cell, but there are two identical bulbs, them it is possible to arrange a row, and on one of them to give a signal from the amplifier or the transmitter, and on another - from the power supply. Adjustment of output voltage of the last achieve that both bulbs shone with identical intensity then read indications of the voltmeter and the ampermeter and calculate power as it is described above.