If you are looking for AC power measurement. To use it just a little, which is not worth it. When we need to buy an expensive tool. Because use little does not need high accuracy. I would like to propose the concept of wattmeter circuit in such a way easy as it was.I collected all three circuit, as follows.
Easy in-line rf wattmeter circuit
This is a little ideas of Easy In-line RF wattmeter circuit, it is insensitive to frequency, so calibration will be correct better than a wide frequency spectrum.
For example the whole amateur HF spectrum; If the values of L2,
the voltage divider at capacitors C1 and C2, and the resistances of R1 and R2 are selected right, R1-R2 and C1-R2 should be matched for best outcome.
Usually, The R1 and R2 must be small compared to the reactance of L2, for to avoid any important effect on the current of L2 , which is induced by the transmission line current flowing through L1.
The lower frequency limit of the bridge is defined by the R1-R2/L2 ratio,
and the cut off point at the value of R1-R2 becomes great with reference to the reactance of L2 at that frequency point.
The amp meter is 100uA – 200uA, it is limited current by the R6.
The S1 uses to choose a range of frequency to Low or High.
Power line frequency meter
This is the meter show the frequency of a power generator, which it has voltage 110V-240V at 10-100HZ.
The output sine waves are converted to square waves by the 100k 2 watt resistor and the 6.8V 1watt (1N3829A) zener diode.
Then the square wave is transformed by the 0.22uF capacitor and the current is averaged by the 1N4148 diodes.
The average current is proportional directly to the frequency, so can read on a 100mA amp meter (M1).
To calibrate, book the circuit up to a 60Hz. Power line and adjust the VR1 5K pot to read 60mA.
Simple led watt monitor
This circuit is the principle of divided voltage. And current divided. Before you take the LED display up to 80 Watt. Operation of the circuit when current is flowing into the resistance. It will divide the voltage to suit each watt range. It has a resistance of 100 ohms to reduce the flow before LED. While the LED display will light sort indefinitely. Depending on the number of watts. For example, a 10-watt LED1, LED2, LED3 will light all. Try to see if the observation that even high-watt. Resistance to Divided voltage is more costly too. That is, resistors R1, R4, R7, R9, R11 and R13 determines the area to the circuit watt.