DrDAQ is a versatile instrument that connects to the USB port of any PC. Using the supplied PicoScope software it can be used as an oscilloscope, spectrum analyzer and signal generator.
The PicoLog graph below shows the measured results.
The results appear to show a cycle occurring daily between Monday and Friday. The voltage at night rises to around 240 volts. During office hours, the voltage drops significantly below 240 V, which may indicate a higher demand on the National Grid. This higher demand is probably due to heavy plant machinery and office usage.
During the weekend, the voltage is generally at a higher level and does not show the daily fluctuations described above.
Using PicoLog, the Minimum, Maximum and Average values for the mains voltage and frequency were recorded and calculated as shown below:
Originally, the UK mains voltage supply was specified at 240 V RMS ±6%. Some while ago, the specifications were changed (230 V +10%, –6%) to allow harmonization across Europe. The average value clearly indicates 240 volts.
At first sight, the spikes in the frequency data are outside the specified tolerance, indicating that the generating company is not meeting their published specification. Closer research into the specification small print shows that the frequency is allowed outside the specification provided that the average frequency over one minute is within the spec. The experiment sampled the frequency every thirty seconds, and therefore the spikes are reasonable. A one minute sampling rate would be more suitable for checking compliance.
This experiment was written by James Carey at Pico Technology.