Quartz furnace
A heated quartz oscillator , sometimes called quartz oven and English Oven Controlled Crystal Oscillator designated (OCXO), a crystal oscillator , which in a heated and temperature-controlled is housed chamber. The quartz oscillators used in quartz oscillators are subject to a small thermal dependency of the oscillating circuit frequency , which is important for precise applications , which is also referred to as thermal drift. By regulating the temperature of the quartz crystal and the oscillator circuit to a value above room temperature, the oscillating circuit frequency can be stabilized and thus a higher accuracy can be achieved than without heating.
General
In contrast to temperature-compensated crystal oscillators (TCXO), which minimize the annoying temperature-related frequency deviations by means of temperature measurement and calibrated correction values, the influence of temperature on a heated crystal oscillator is minimized by active heating and keeping the temperature at a constant high level. Applications of heated quartz oscillators include simple frequency standards and digital frequency counters , where higher accuracy is required than with non-stabilized quartz oscillators and, at the same time, less accuracy than atomic clocks can be tolerated.
The typical operating temperature is +75 ° C, but depending on the specific type and application, it can be in the range of +30 ° C to +85 ° C and is agreed with the quartz manufacturer. The AC cut and SC cut are used as quartz cuts for the quartz used in the furnace . A selection criterion for the temperature to increase the stability is that operating point where the crystal frequency as a function of the temperature has no or only the smallest possible slope. A further improvement results when power transistors are used as heating elements in the furnace instead of heating resistors . The reason is that the heat loss from bipolar power transistors is directly proportional to the current, while heating resistors have a quadratic dependency. The quadratic dependence makes it difficult to keep the temperature constant.
The short-term stability of heated quartz oscillators for several seconds is about 10 -12 , the achievable long-term stability in the range of 10 -8 , which is in operation to several days depending on the type achieved after a few hours. The relative value 10 −8 corresponds to a maximum deviation of 1 Hz at an oscillator frequency of 100 MHz.
The following table shows a comparison of the data for some oscillators:
| Oscillator type | rel. Measurement uncertainty | Aging / 10 years |
|---|---|---|
| Crystal oscillator | 10 −5 to 10 −4 | 10 to 20 ppm |
| Quartz furnace (OCXO) 5 to 10 MHz 15 to 100 MHz |
2 × 10 −8 5 × 10 −7 |
2 × 10 −8 to 2 × 10 −7 2 × 10 −6 to 11 × 10 −9 |
| Rubidium atomic clock | 10 −9 | 10 −12 to 10 −11 |
| GPSDO | 4 × 10 −8 to 10 −11 | 10 −13 |
| Atomic clock ( Cs ) | 10 −11 to 10 −12 | 10 −12 to 10 −11 |
literature
- Bernd Neubig, Wolfgang Briese: The large quartz cookbook . Franzis-Verlag, 1997, ISBN 3-7723-5853-5 ( online ).
Individual evidence
- ↑ Temperature Controller for Crystal Oven , FreeCircuitDiagram from May 2, 2009, (Engl.)
- ^ Frerking Marvin E .: Fifty years of progress in quartz crystal frequency standards . Institute of Electrical and Electronic Engineers. Pp. 33-46. 1996. Archived from the original on May 12, 2009. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved March 31, 2009.
- ↑ Time and Frequency from A to Z ( Memento of the original from September 15, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , NIST glossary, (Eng.)
- ↑ a b c Tutorial Precision Frequency Generation Utilizing OCXO and Rubidium Atomic Standards with Applications for Commercial, Space, Military, and Challenging Environments IEEE Long Island Chapter March 18, 2004 (PDF; 4.2 MB) Retrieved January 31, 2011. 091116 ieee.li
- ↑ z300 High Precision Time Server synchronized by GPS (PDF; 512 kB) Archived from the original on July 18, 2011. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved January 31, 2011. 091117 zti-telecom.com
- ↑ Time and Frequency - Precisely the Way You Need It Time and Frequency - Precisely the Way You Need It (PDF; 188 kB) Retrieved on January 31, 2011. 091118 spectruminstruments.net
- ↑ GPS Time and Frequency Reference Receiver (PDF; 2.1 MB) Retrieved January 31, 2011. 091118 leapsecond.com
