Electronic Development Corporation
Current and Voltage Standards models CR103 and MV106

Serial numbers 8018 and 7706

Model CR-103/J (the top unit shown here) is comprised of two complete instruments. The DC voltage section is an ultra-stable, chopper stabilised amplifier with selectable precision resistors in the feedback loop. The temperature compensated, aged zener diode is the reference for the entire instrument. The DC current section is essentially the same configuration plus a precision, reference resistor.

DC Current: Two ranges ▒10nA to ▒100mA DC High Resolution: ▒0.0001% (1ppm) of both ranges Minimum selectable setting: 10nA
DC Voltage: 10V, ▒11.11110V DC; 100mV, ▒111.1110mV DC; 10mV, ▒11.11110mV DC Resolution (1ppm): 10V, 10ÁV; 100mV, 0.1ÁV; 10mV, 0.01ÁV
source: http://www.krohn-hite.com/htm/calibrators/edcmodelcr103.htm

Model MV106 is a precision voltage standards/sources that are highly versatile references designed to meet the needs of computer systems, production line testing, automated calibration systems and standards laboratories. The MV106 provides 3 voltage ranges which include 10mV, 100mV and 10V. Resolution is 0.01ÁV.
Output: 10V, ▒11.11110Vdc; 100mV, ▒111.1110mV DC; 10mV, ▒11.11110mV DC Resolution (1ppm): 10V, 10ÁV; 100mV, 0.1ÁV; 10mV, 0.01ÁV
source: http://www.krohn-hite.com/htm/calibrators/edcmodelmv106.htm

Model CR-103/J interior

Model MV106 interior

Both instruments were working when I received them but on both of them the decimal point lamps were defective. On the MV106 I managed to remove the one defective bulb and replace it with a Christmas tree light in series with a resistor. On the CR103 I had less luck and ended up replacing all three with red LEDs in series with a resistor. The open circuit supply voltage on both models was 32 Volts. These pictures were taken before modification.