Frequency setting of rubidium oscillator
(Description of 2005.10 month 27 renewal FE5680A was added)
Several rubidium frequency standard was procured recently at the certain place
As for the manufacturer as for FREQUENCY ELECTRONICS type you call FE5650A.
Because small-sized (approximately 75 x 75 x 40mm) it is extraordinary, funny so is in the one for various installation.
However procuring, when it tries measuring frequency 8.388608MHz (2~23Hz) with at special frequency general
It was not 10MHz frequency
It is to download the catalog from the sight of the manufacturer but concerning Option 58 there is no description in the catalog,
The special item it was found that it seems.
Page of product information of FEI corporation
According to the above-mentioned catalog this rubidium with factory option can set frequency from 1Hz to 20MHz, so is.
(However at the time of rectangular wave at the time of 1Hz~10MHz sine wave 5MHz~20MHz)
With it tried challenging to the modification of frequency with thing
Photograph 1. it is the rubidium which this time is procured.
Photograph 2. synthesizer baseplate
Enlargement of photograph 3. synthesizer baseplate
DDS, AD9830A of the analog devices corporation is used in the synthesizer.
50.255055MHz of 1/136 of resonance frequency 6834.6875MHz of rubidium has entered into that clock.
It can set optional frequency by the fact that the specification of this DDS is modified.
As for the resonance frequency of Rb87 according to the literature with 6834.6826128MHz PRS-10 and the like of SRS has become this frequency, but
Why things such as the EFRATOM corporation and the FEI corporation has become 6834.6875MHz. This perhaps pressure and the buffer gas of the gas cell
You think as the thing due to the difference but as for details it is not understood. When someone more detailed one is please teaches
Two push button switches are visible in other things, but as for this one side already with increase of specification one side with decrease
You forgot, but if it tries pushing, you know immediately either one either one. As for the result of pushing the button being remembered
Turning off power, it is not cancelled, because when there is no necessity, please make sure not to touch
If it is fine control, it can set even here.
Photograph 4. communication port
Photograph 5. communication cable
As for actually setting method making this kind of cable, from the serial port of PC
Sending command to the controller on the baseplate, it sets frequency.
As for the communication software the hyper terminal which belongs to Windows was used
Because you do not use special function, as for the terminal software you think that it is good with anything.
As for communication type
Baud rate 9600 data bit number 8 stop bits 1
Parity it is not there is no flow control
Is.
Communication method
First S (CR) with please strike from the keyboard
(Note. (CR) It is the Enter key on the keyboard. Also operation below is similar.)
When it does, from the controller
R=50255057.015837Hz F=2ABB504000000000
OK
With there is the response which is said. (As for this as for numerical value it changes with one example with the individual.)
As for meaning of this value
Frequency and F= where R= has entered into DDS are the specification of DDS.
Then from keyboard
(CR)
Specification changes that with it inputs. (part is the hexadecimal number of 8 columns.)
Return value from the above-mentioned controller is 16 columns, but because the value which is input is 8 columns, way you do not make a mistake,
As for the numerical value of R= it is possible to modify in the same way, but changing this numerical value, at all without happening, it does.
Somehow as for this value recording the frequency when proofreading, you use for calculation as a calibration value when the setting F=
It is like it does.
When E (CR) with it inputs lastly, the above-mentioned frequency is remembered.
Unless this is executed, when power is turned off, because it returns to original value, please pay attention
It is completion of setting at above.
Calculation method of specification
As for specification it is something which describes the value of 32 pits which set to DDS that way at the hexadecimal number of 8 columns.
As for details downloading the data seat of AD9830 in the home page of the analog devices corporation
Please read that
When with you write, because it ends, just you explain a little.
Because the frequency which is input into DDS (R) with bit number of the accumulator of DDS is 32 bits
Per specification 1 bit
R/(the 2~32) = 0.01170xxxxx (Hz) it becomes.
Then for example intended frequency when it makes 10MHz
F= 10000000/0.0117xxxxx = 854633852
When this is inscribed at hexadecimal number
F=32F0AD7C
With it becomes. Because (to the last it is one example, ramming down this way, it becomes 10MHz with it does not limit accurately)
(As for note frequency being like it is restricted to 5MHz~20MHz with the program of PIC, when it sets outside the range, there was a thing which does not operate just)
Other attention points
To set frequency with approximately 0.0117Hz step, because it is odd value, this way with specification largest approximately 0.006Hz
Error occurs.
When frequency is modified frequently, how it will do it is not, but when you use at fixed frequency, with the trimmer of the photograph under
Somewhat, if (±0.01Hz rank) is, you can adjust.
However in order (naturally) to adjust this, it had the frequency standard and the resolution below 0.001Hz which had the precision above equality to this
The frequency comparator becomes necessary.
Photograph 5. frequency adjustment
Trying modifying the frequency of this frequency standard machine lastly, in various ways it means that the air is attached but with the catalog specifications
周波数 frequency range 5MHz~20MHz be be but 11MHz above frequency at output level decrease see
As for the upper limit of the practical operating range with 18MHz or 19MHz level being too low with 13~14MHz, you understood whether cannot be used
Because (among of the beginnings saw only frequency, the air was not attached directly)
As for this you think as the for the sake of the low-pass filter of the output of DDS with 8.38MHz is made in optimum operation.
That you think. whether (it is not the reason where here becomes factory option,)
That with constant modification of the low-pass filter to 15MHz rank, you think it is possible but above 17MHz frequency of DDS peculiar [supuriasu]
Because it gets near, perhaps it to be necessary also for BPF to jointly use not only LPF,
The rubidium, FE5680A (2005.10 months)
In addition of recently anew the rubidium new type was procured
As for this as for size it is larger than description above, is, but thickness is thin in 25mm and the emergency, is.
Photograph. It is the rubidium which this time is procured.
It is inside.
Inside part there is a part which is different, but it is the same as those on the majority.
Also frequency modification was possible with similar method
You do not open the fine control of frequency and you are possible with adjustment of the trimmer where also the [te] is visible from the groove of the case.
To the last because it is memorandum concerning setting method like this doing, it was good and did not go
It does not accept the claim such that the oscillator of the treasure was broken and the request for modification of oscillation frequency
In addition either sale of this standard has not done
Looking at this, we ask the one which is executed to the last on self responsibility.
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