In this episode Shahriar dives into the concept of a capacitance bridges. In particular, the Andeen-Hagerling AH2500A Ultra-Precision Capacitance Bridge:

https://www.andeen-hagerling.com

The theory of operation is explained in details alongside a comparison with more traditional LCR meters. A simple replica transformer-based bridge circuit is also used to demonstrate the principle operation using a Zurich-Instruments MFIA lock-in amplifier. The teardown of the unit provides further insight into the engineering design of the instrument.

The capacitance bridge is also used to measure small shifts in a parallel plate capacitor. Furthermore, a complete set of air capacitor standard modules are calibrated & adjusted using the bridge as a standard.

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In this episode Shahriar take a look at a broken Chub. These instruments are able to measure PRTs, Thermistors as well as other resistive based thermometers. They can also be quipped with thermocouple reader modules.

This specific instrument has a blown fuse and draws an excessive amount of current. The first problem is a faulty 5V DC/DC converter. Although changing the IC does resolve the 5V power supply problem, it is likely that the failure has also caused excessive voltage to appear across the unit. There is no activity from the microprocessor. After replacing the processor and re-programming the EEPROM, the unit is up and running. A few experiments with various sensors and precision resistors verified the functionality of the instrument.

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