To programmatically read all 500 harmonic orders measurement values, please use the ":NUMERIC:LIST" command set.
Please refer to the attached file taken from the Communications Interface Manual.
The WT1800 Power Analyzer offers maximum flexibility with up to six wattmeter elements, high bandwidths, simultaneous high speed digitizing, and wide voltage and current ranges. Although this model is still available, the newer WT1800E offers higher accuracy.
Measure characteristics of devices that generate, transform or consume electricity. Also called power meters or wattmeters, these devices measure parameters such as true power (watts), power factor, harmonics, and efficiency.
Yokogawa's Power Analyzer software manages numeric, waveform, and harmonic data measurements. It enables data logging and instrument configuration from your computer.