Development of multi-functional grounding resistance meter based on DSP

According to the present development of the grounding resistance testing system, the paper designs a new multi-functional inverter grounding resistance meter based on BF504 chip. It's forward channel acquisition circuit to get information of the grounding resistance by testing terminals and clamp mouth, using AD7942 chips to get real-time data of voltage and current; after data processing by DSP to get related parameters of grounding resistance, finally realizes the docking ground resistance measurements. Using direct digital frequency synthesis (DDFS) technology to automatic frequency selection, avoid interference frequency. After testing, the results show that the instrument is reliable, high accuracy, low cost, compact and lightweight.