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This description outlines the design and construction of an oven for an UI precision calibrator. As quantitative investigations have shown, the temperature coefficients of the active components and resistors, as well as the numerous thermocouples on the PCB, significantly impair the accuracy of the device. For this reason, a temperature-controlled oven is required in which ─ apart from the reference source ─ all other sensitive components are also decoupled from environmental influences.

The bipolar calibration unit (still under construction) provides output voltages of ±10 V, which can be set with a resolution of 20 nV thanks to the 20-bit precision DAC AD5791. The current source using the AD8276 difference amplifier delivers output currents of up to ± 100 mA in 200 nA steps. 

The topology of both, the voltage and current source largely corresponds to the Analog Devices application notes [1] and [2].
Vincent on ElektorLabs had already realized this concept with an impressively compact design for the calibrator [3].
 Later, he upgraded the device with oven stabilization for the MAX6350 reference voltage source to enhance the thermal stability.

The present project incorporates all these ideas. However, since the device is designed to be a bench-top unit, further improvements regarding temperature stability, supply filtering, noise suppression, and long-term drift can be integrated into the design.

This description outlines the design and construction of the oven for the bench-top unit; see attached document: Oven Controller for UI-Calibrator_en_V3.pdf.
The report of the UI calibrator will follow later. 

To minimize temperature drift effects, all active components and resistors associated with reference voltage generation and signal conditioning are housed in an oven.
 This includes all thermocouples within the PCB circuit that are mainly formed by the solder joints.

The oven is maintained at a constant temperature of 50 °C and operates continuously to prevent temperature hysteresis.
 The overall power consumption of the device is less than 3 Watts.

The oven, containing the relevant components, is located beneath the main circuit board, while the capacitors are positioned on the cooler top side (outside the oven).

The attached document describes the development steps, such as the design of the PI controller using the results from step response tests, the construction of the oven itself and the manufacturing of the PCB.

An initial functional test demonstrated that the oven maintains a stable temperature ─ even during rapid fluctuations in external temperature ─ within a tolerance range of less than 0.5 °C .
 This fulfils an important requirement for the precision calibrator.