Frequency Meters
This portable frequency meter measures electrical signals across a wide range—from the slow pulses of power systems to the fast switching of radio and computing circuits. Functionally identical to the earlier Sinclair PFM200, it was rebranded under Thandar Electronics following the 1979 restructuring of Sinclair Radionics by the UK’s National Enterprise Board. While Clive Sinclair distanced himself to focus on new ventures, the existing instruments department continued under new leadership and developed a reputation for reliable engineering.
The PFM200A updated Thandar’s earlier pocket frequency meter with a simplified two-socket input system. This redesigned input stage made the device easier to operate and better suited to a wider range of electrical environments, while still covering the same broad frequency range. Used to measure signals from audio tones to high-speed circuits, the PFM200A reflects Thandar’s effort to modernise Sinclair’s original design and improve usability for technicians working in the field or workshop.
The TF040 was a compact frequency meter designed to measure signals up to 40 MHz—suitable for audio, radio, and other low- to mid-frequency electronics. Its low-power LCD screen and energy-efficient circuitry gave it long battery life, making it practical for extended fieldwork. Although limited in frequency range, it included a rear connector for an external add-on unit, reflecting a modular approach common in portable test equipment of the time.
With an extended frequency range up to 200 MHz and added features, this frequency meter offered technicians greater precision and flexibility. Its LCD screen and low-power LSI (Large Scale Integration) circuitry made it ideal for portable, battery-powered use. It included selectable timing modes, an external clock input, and could be paired with an optional prescaler to expand its capabilities—making it a more versatile tool than the previous TF040 model for both general and advanced testing needs.
The TP600 was an add-on device designed to extend the frequency range of compatible Thandar meters. Known as a “prescaler,” it worked by dividing very high input frequencies by ten—allowing a frequency meter to process signals up to 600 MHz that would otherwise exceed its limits. Compact and lightweight, it could be powered directly from Thandar’s TF040 or TF200 meters. This modular approach gave users a cost-effective way to expand their testing capabilities.
The TF600 extended the series’ reach, measuring frequencies from 5 Hz to 600 MHz—spanning everything from slow timing signals to fast broadcast transmissions. Unlike its LCD-based predecessors, it featured a bright LED display for immediate readability in varied lighting. Two separate inputs supported low- and high-frequency ranges, offering greater accuracy and signal isolation. Designed for both portable and benchtop use, it reflected Thandar’s effort to offer a wider range of tools for different users—from general electronics servicing to more advanced testing needs.