In this episode Shahriar experiments with a SunPower CryoTel Mini Cryocooler:

https://www.sunpowerinc.com/products/stirling-cryocoolers/cryotel-cryocoolers/ds-2_1

A three-stage turbomolecular vacuum system is used to reach very low pressures of 10E-6 Torr to provide a suitable environment for the cryocooler. Unfortunately, due to the age of this unit, the maximum applied power is limited to 22W. Despite this, reaching temperatures of -210C is possible with no thermal load. A custom heater element is also used to inject thermal energy into the cold tip and measure the available lift from the engine. A new GUI is also developed to control the cryocooler, measure the cold tip temperature, rejection temperature and applied power as a function of time. This allows several cryocooler modes to be explored.

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In this episode Shahriar explores the mechanism and reasons for fiber optic polarization scramblers. The video discusses the many fascinating methods for embedding data onto fiber optic links. Amplitude modulation, phase modulation, dual polarization (MIMO), wavelength division multiplexing, & spatial division multiplexing are all discussed. The overall architecture of typical coherent optical communication systems is also discussed.

With the theory of coherent communication in place, we can dive into the importance & application of such a polarization scrambler instrument. We further dive into how the unit works followed by a complete optical test system which characterizes the polarization scrambling capabilities. Lastly, a complete teardown shows the ultrasonic, multi-segment transducers which induce birefringence on the fiber segment and cause polarization scrambling.

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In this episode Shahriar asks an AI LLM to solve problems from the final exam of a metrology & instrumentation course intended for electrical engineering graduate students.

We also do some experiments to verify the theory from one of the questions. Let’s see how well AI can tackle these problems!

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In this episode Shahriar repairs a Keysight 53230A frequency counter with an unusual problem. The instrument reports OVERLOAD for both high & low thresholds on both Channel 1 & Channel 2 with or without an input signal. With this problem, the instrument also fails self-test.

There is no schematic or even a block diagram for this instrument. But since the unit is equipped with both the Microwave Pulse Measurement as well as the 15GHz Microwave input option (as Channel 3), it is certainly worth repairing. Channel 3 of the instrument is fully functional, which is a good sign for the health of the latter DSP portion of the unit.

Teardown reveals two parallel & identical Channel 1 & Channel 2. The circuits are examined in details and the primary comparators are identified. After some testing, it becomes clear that the comparator thresholds are controlled via some ADI DACs which are maxed out due to inactivity at the output of the comparators. Interestingly, the latch inputs ports of the comparator ICs are also controlled by a different DAC. This is the first part which is in common with both channels. After replacing this DAC, the instrument no longer reports the OVERLOAD error.

The instrument is also upgraded with an OCXO which should bring much better frequency stability. The unit is then calibrated against a Rubidium standard. The microwave pulse measurement is demonstrated first using a R&S SMBV100B Vector Signal Generator & Tektronix MSO-6B Mixed-Domain Oscilloscope. The Keysight 53230A is easily able to measure pulse duration, repetition as well as the carrier frequency. The frequency counter's trend chart, histogram & other advanced DSP functions are also demonstrated.

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In this episode Shahriar re-traces history and measures an important characteristics of a fundamental sub-atomic particle: the charge to mass ratio of an electron.

This experiment, first performed in 1897 by J.J. Thomson, changed physics by showing that atoms are indeed made of further sub-atomic particles through the discovery of electrons. We build a setup using a pair of Helmholtz coils, a cold-cathode vacuum tube driven by a multi-kV DC power supply & careful measurements of the beam deflection angle. The theoretical foundation of the experiment is described in details.

The measured e/m ratio is compared with the NIST established number with great agreement. The historical impact of the work of J.J Thomson & Robert Milikan (measuring the charge of an electron) are also presented.

The two winners of the giveaway are:

@nicolasblomstrand2912 (YouTube)
Robert S. (Patreon)

Each will receive a Siglent SDS1104X HD!
https://www.siglentna.com/product/sds1104x-hd/

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