Additional Features: Measure Current from 1fA to 20mA Source Bias Voltage from 500μV to 100V Programming Language and Remote Interfaces Reading and Setup Storage The Keithley 2500 Dual Photodiode Meters can measure and display either photodiode current or optical power for two photodiodes with appropriate user-supplied optical power gain/wavelength calibration factors. The Keithley 2500 Dual Photodiode Meter combines two stable DC bias voltage sources with two low-noise ammeters for dual-channel, low-current photodiode measurements. The unit has 0.1% basic measurement accuracy with up to 6.5-digit resolution. At 5.5-digit resolution, the Model 2500 can transfer up to 475 readings per second over the GPIB, and up to 900 readings per second with 4.5-digit resolution.