Navigation:  Tutorials > Power module tutorials > Single phase power measurement > DEWESoft 7.0  data acquisition, processing, analyzing and storage software Measurement

Let's go to the overview screen and create a display for power parameters. Additionally, there are two visual controls available in the control tool box, if we have at least one power module in the setup which  includes vector scope and harmonic FFT.

 

So let's place a vector scope at the top, which shows the phase relations between voltage and current. We can see there is a phase angle between voltage and current, since there is an electro motor inside the hair dryer. The recorder on the top right shows the period value of the current, showing how the hair dryer was switched on or off.

The bottom right scope shows the voltage and current and we can see nicely how the hair dryer is only operating at half power. The current on the lower part is cut because of regulations. We can see this behaviour even better with speed variable tools like a drill.

On the bottom left there are two harmonic FFTs, where the upper one shows the voltage and the lower one shows the current harmonic. We can observe nicely that the 5th harmonic of the voltage has approximately 7% of the line voltage value, while the current has many harmonics, due to the regulation circuit.

 

Now let's observe these characteristics at full power. The current is taken from the full cycle and the phase angle between voltage and current is much lower. Also, the current harmonics have dropped significantly are following the voltage harmonics.

 

Now let's do make another test - observing the difference between a normal and an energy saving light bulb.
First let's connect the energy saving light bulb. I have used a 11 W light bulb, which should be similar to a 60 W normal light bulb. The total power is indeed very low, but the shape of the current is not really a sine wave. Therefore we have lots of harmonics of the current, which "pollutes" the power grid.

 

Now let's take a look at the classic 40 W light bulb. The first thing to notice is that the load on the grid is linear to the voltage. The measured power is exactly 40 W, but the vector scope looks strange. In fact, since the light bulb is a purely ohmic load, the voltage and current should be perfectly aligned, but as we can see, they are not. What is the reason for this? Remember the voltage and current tutorial where we have seen the difference between the current clamps and the shunt resistor? Since we are using the current clamps, we have amplitude and phase errors. As a result, the current clamp is main source of the calculation error in this case.

 

In DEWESoft we have a chance to compensate for these errors. Let's take a look how.