This is a continuation of the previous two circuits. This circuit controls the temperature in a miniature oven that holds a stable dual voltage reference.
Temperature Measurement and Control
In colder seasons or locations this will maintain the temperature at a higher level. A mini fan in the equipment ensures external heat does not reach the oven, fan keeps the larger chassis cool.
LM399 is a Precision Reference chip. From this a dual polarity mirrored reference is derived using OP07 op-amps. This assembly is mounted in a miniature oven to ensure temperature stability.
Instrumentation and Measurement Circuits
The oven used Two Steel Boxes one mounted in another with Glass Wool In-between to reduce heater losses. Steel was used to ensure excellent EMI-RFI Shielding. Both the outer and internal shell was earthed.
This is part of a precision High Voltage but Low current Power Supply for Testing leakage currents in passive devices. This Supply is a module for a Automatic Test system in component inspection.
HV Precision Power Supply Circuits
Insulation of Transformers and the Isolation of plastic capacitors are best analyzed by applying a High Voltage and measuring the leakage currents.
These currents are in the order of nano-amps and pico-amps; values close to the bias-currents and leakage currents of devices. Some offsets and corrections can be done in software for the ATE systems.