ERMA PH-8424 PH meter ORP meter Tester is a highly accurate, portable pH/mV meter. It is one of the most popular pH meters on the market. This instrument is able to perform pH, mV and temperature measurements with a high degree of accuracy and fast response. Users can exchange the pH probe for an ORP probe to obtain ORP readings in the mV range. Besides, the special electrode can be replaced, which is suitable for measuring the pH of beauty, soil, fruit and milk, etc.