Measuring instruments Prostat PAS-ESI 870 Resistivity Indicator Resistance and Resistivity ASTM D-257 61-100-0404 Prostat PAS-ESI 870 resistivity indicator: measures surface resistivity and resistance to ground per ASTM D-257. 2 display units (resistance + resistivity). Range: 10³–10¹² Ω. 40–60°C. Portable.