The Model 487 is designed for measurement of low currents and very high resistances. This instrument incorporates all the capabilities of the 486, and adds a programmable ¡ 500V source. This combination of picoammeter and voltage source provides a powerful high resistance meter and fast picoammeter in one instrument. The 487 makes current measurements from 10fA to 2mA. Two voltage source ranges are available: a 500V range with 10mV resolution and a 50V range with 1mV resolution. A PRESET button allows the user to toggle between two separate source values. The 487 sources up to 500V, measures the current with 10fA sensitivity, and then instantly calculates the resistance value, from 500m Ù to 5 ¡¿ 1016 Ù. The unit displays either current or resistance. Reading intervals from 10ms to 1000s can be programmed, simplifying tests that require a predetermined ¡ soak¡± time.