Now You Can Buy the Smallest Atomic Clock Ever Made

Now You Can Buy the Smallest Atomic Clock Ever Made
The new clock, precise to a millionth of a second, is 100 times smaller than its predecessor

By Julie Beck


World's Smallest Atomic Clock Symmetricom

If you have a spare $1500 burning a hole in your pocket, perhaps you’d like to spend it on an ultra-precise, ultra-small atomic clock, now available for purchase from Symmetricom Inc. Draper Laboratory and Sandia National Laboratories.

The Chip Scale Atomic Clock (CSAC), originally developed for DARPA, is 100 times smaller than its predecessors and uses 100 times less power as well. It requires only 100 milliwatts of power, measures about 1.5 inches per side and is less than half an inch deep.

The clock measures the passage of time in millionths of a second by counting the frequency of electromagnetic waves. These waves are emitted by cesium atoms are stored in a tiny container, no bigger than a grain of rice, when they are shot by a vertical-cavity surface-emitting laser (VCSEL). Replacing the previously used rubidium-based atomic vapor lamp with the VCSEL is what reduced the clock’s power consumption.
Measuring The Wavelength of CSAC's Laser: Randy Montoya/Sandia National Laboratories
A CSAC clock continues to function when GPS signals are blocked, making it incredibly useful deep underground or underwater. It could also prove handy when experts are blocking telephone signals from detonating explosive devices with electromagnetic interference, as the CSAC would continue to function.

After 10 years of development, CSAC went on the market in January. DARPA projects rarely become commercialized, so this product page, available for anyone to peruse on the web (and purchase for their deep-sea explorations), is a pretty big deal.



Atomic clock accuracy and low power make the SA.45s ideal for portable applications requiring precise synchronization and time keeping, especially in GPS-denied environments.

Breakthrough Leadership The CSAC’s unmatched portability derives from specs that include:

115mW power consumption
16cm3 volume
35g weight
±5.0E-11 accuracy at shipment
σy < 5 x 10-12 at τ = 1 hour short-term stability (Allan Deviation)
<3.0E-10/month aging rate

A New Class of Applications At two orders of magnitude better accuracy than oven-controlled crystal oscillators (OCXOs) — and up to four orders of magnitude better accuracy than temperature-controlled oscillators (TCXOs) — the CSAC’s unmatched portability opens the door to new classes of applications, such as:

Underwater sensors for seismic research or gas and oil exploration
Military systems including dismounted IED jammers, dismounted radios, GPS receivers, and unmanned aerial vehicles (UAVs)

Device Connectivity The SA.45s CSAC produces two outputs, a 10MHz square wave and 1PPS, both in a CMOS 0 – 3.3V format. It also accepts a 1PPS input for synchronization and provides an RS-232 interface for monitoring and control.



The SA.45s Chip Scale Atomic Clock (CSAC) is available in two versions:

Option 001, which operates from -10° C to +70°C for commercial applications
Option 002, which operates from -40°C to +85° C for military applications

A CSAC Developer's Kit is also available.
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