Keithley calibration and verification sources have been designed to calibrate capacitance measurement equipment operating at frequencies to 1MHz. The sources are configured for 3-terminal (shielded) capacitance and conductance measurements. They use stable glass dielectric capacitors and high-quality film resistors, both with very low residual impedance. The sources are specified at 1kHz, 100kHz, and 1MHz, and the conductance sources are specified at DC, 100kHz, and 1MHz. Their calibration is traceable to the National Institute of Standards and Technology. The Model 5907 Calibration Capacitors can be used to correct for 1MHz connection errors in the Model 590.