Stanford Research Systems
PRS10 Rubidium Frequency Standard

Brooke Clarke 2000 - 2007

Stanford Research Systems
          PRS10 Rubidium Frequency Standard
Appliations
Bench Operation with Optional PRBB
Bench DC Power Supply
Block Diagram
Programming
Acceleration Effect on 10 MHz Xtal
Rb monitor Software from SRS
Aging Rate
Patents
Links

Applications

Bench Operation with Optional PRBB

My bench supply only has 1.0 Amp capacity and the startup heater power requires 2.2 Amps.  Since the current draw after warm up is less than 0.6 Amps I connected 2 each 12 V gel cell batteries across the power supply and added a diode to isolate the power supply in case the power fails.  The batteries supply the extra current needed during warm up and power fail protect.

Bench DC Power Supply

Mouser carries a Phihong 552-PSS-45W-240 45 Watt power supply for$37.60 that has the correct 2.1x5.5mm plug to connect directly to the PRS10 power socket.  They also have the IEC EN603020/C7 line cord as Mouser # 173-21101.  This is typically the 2 wire cord used for Laptop AC power modules.

Have been using the Phihong power supply instead of the HP lab supply in order to free up the HP.  The down side is that the PRS10 shuts down during a power failure, but that's OK since all the other test equipment alos shuts down.

Block Diagram


 Programming

 The PRS10 manual details the RS-232 commands.

I have started to write some LabVIEW code to work with the PRS10.
A plot of the Frequency Control word "FC" (22 bits) sent to the 10 MHz Xtal oscillator shows what that crystal is doing.  Remember it's output is always 10 MHz so that the changes in the control word indicates what would have happened without the Rb lock.  You can easily  see temperature and load changes.  Also for a number of hours after start up you can see the Xtal settling into a stable state.

Frequency Synthesizer

This LabVIEW program now reads all the synthesizer parameters.  Here is a screen shot (LV_Synth.jpg)

Physics Package

Consists of: Here is a screen shot Phy.jpg showing the front panel of the LabVIEW program.

Acceleration Effect on 10 MHz Xtal

Just to see the effect of Gravity on the 10 MHz crystal I rotated the PRS10 from heat sink fins up, to fins on the right, fins on the bottom, fins left and back to fins up.  Here is the FC plot showing the movement. (Note that on the FC plot 1 count is close to 1E-12). FC_ROT.jpg

Rb monitor Software from SRS

To support the newer bench top version of the PRS10, called the FS725, SRS has a free software package that reads all the parameters from the PRS10 or FS725 once each second.  I use an Edge Port box with 4 serial ports that connects to the computer via USB, so am using COM5 for the PRS10 and the software supports this port.

What they didn't tell you is to go into My Computer and set the COM port parameters for:
9600 Baud, 1 stop bit, No parity and Xon/Xoff protocol, if you don't do this it will not work.
A simple check is to type "ID?<cr>" into the message box and see if you get the ID string back.

Real Time plots of the performance of a PRS10. Driven from a Motorola UT+ with the latest firmware that has the sawtooth spike bug fixed.

Aging Rate

When my house GPS antenna system quit working the PRS10 was not getting it's 1 PPS to steer the Rb, but becasue the aging rate for Rb is so much better than a crystal, I can keep using it as my house standard without the updates and still measure the aging rate of a crystal oscillator.

Patents

Class 331/3 has a lot of atomic clock patents most are Rb

Links


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