RI Title
RI logo


This document provides factory and field procedures for calibrating and independently verifying the 10 MHz time base in the Cassini system. This should NOT be performed during annual calibration. The offset identified at the factory will be sufficient for the lifetime of the tester, EPC can be returned to factory after 10 years for Cal after verification.



IMPORTANT: As of 2018, Cassini and Guru work together to initialize the RIFL master based on this file and the local Guru ID. Please follow the EPC Exchange Checklist to guarantee this step is completed correctly. If using a Cassini Short Cut issued before 2018, the offset value is stored in "C:\RI\RiflMasterDef.cff" file.

See this relevant Service Bulletin: Service Bulletin - EPC Exchange (Guru ID from RIFL Hub) http://roos.com/docs/RBEH-9PH2UU?Open

Factory Calibration:

Equipment Required:
Secondary GPS frequency standard, 10 MHz, better than 1e-10 absolute accuracy
Frequency counter, able to count 10 MHz, with external time base input.
Waveform TIM (to access 10 MHz signal) or 10 MHz reference port on RIFL Hub in the Testhead or access to 10 MHz reference port on RIFL Master located in the EPC.
Cassini application initialized for

Factory Adjust 10 MHz Reference:
The 10 MHz time base is part of the RIFL master, and is located in the EPC (computer). It must be adjusted for frequency accuracy. After initial adjustment, the accuracy is good for the life of the tester.

IMPORTANT: the tester must be continuously operating for at least 24 hours before the time base can be adjusted.

1. Connect the counter's time base input to the frequency standard. Be sure the counter is set to 'external time base reference'. If the counter does not display "EXTREF" check the BNC cable coming from the time base standard for proper hook up.
2. Connect the counter to the waveform generator TIM's WF8. Using the control panel, set the sine generator to 10 MHz, 1V P-P. (The sine generator matches precisely the tester time base frequency).
3. The time base frequency should be 10 MHz +/-5 Hz (0.5 ppm)
4. If the time base frequency is not 10 MHz +/-5 Hz, adjust it as follows:
  1. Open the equipment pool window (System > Equip > Nodes). Highlight the 'Master'.
  2. Select Pool > Correct 10 MHz. The tester will open a popup window with the current reference offset value.
  3. Change the reference offset. Note that a change of '5' in the reference offset represents roughly 1 Hz change in the time base. Select OK.
  4. Repeat steps b and c until the frequency is 10 MHz +/-1 Hz.
5. Open the module browser window (from the Equipment Pool window, select Pool > Control Modules). Highlight the 'Master'. Select Node > EE Save Node Info. When it asks if you're sure, select Yes.

Perform a System > Startup, set the sine generator to 10 MHz, 1V P-P again, and confirm that the time base is accurate.

The system time base is now calibrated to be within +/-0.1 ppm. At the maximum specified aging rate, the system will remain within spec for >20 years.

Field Verification/Calibration:

The time base is specified to remain within tolerance for a period of 20 years. Additionally, the 'consensus of time bases' guarantees to a high confidence that the time base is correct. (ref. document Understanding Frequency (Time Base) Accuracy on the Roos 7100A Testers.) However, if independent confirmation is desired, the following procedure can be used:

Equipment Required:

Frequency counter, properly calibrated to better than 1e-8 absolute frequency accuracy, able to count 10 MHz.

NOTE: both the frequency counter and the tester must be continuously operating for at least 24 hours before the time base can be verified or adjusted.

To Adjust 10 MHz Reference:
  1. Connect the counter to WF8. Using the control panel, set the sine generator to 10 MHz, 1V P-P. The sine generator now precisely matches the time base frequency.
  2. The time base frequency should be 10 MHz +/-30 Hz (3 ppm).

If the time base frequency is not 10 MHz +/-30 Hz, adjust it as follows:

Caution: This procedure modifies permanent memory in the tester. Failure to precisely follow this process can result in improper operation of the tester.
  1. From the main Cassini window, choose a system startup (System > Equip > Startup)
  2. After the startup is finished, open the configuration window (System > Tester). from the configuration window, open the diagnose window (Tester > Diagnose).
  3. Run a self test (Run > Self Test).
  4. Hide details for 3)   [Expand for additional instructions for calculating RI7100A offset]3) [Expand for additional instructions for calculating RI7100A offset]
    3a) For RI7100A sources only: Note the 'Ref Offset' for each source. (The Ref Offset represents the reference phase lock voltage, in volts.) Check that the Ref Offsets are centered around 0.
    If the Ref Offsets are not centered around 0, calculate how much the time base needs to change to center all the Ref Offsets around 0. Note that a change of '100' in the time base value represents roughly 1 Volt change in the phase lock voltage.

    Example: If the 'Ref Offsets' at startup are:
    Src1: +3.2, Src2: +2.7, Src3: -1.5, RecLO: +0.4 then Src1 is the highest at +3.2 and Src3 is the lowest at -1.5
    We want to center that around 0, so we want to lower the reference frequency to lower Src1's value by 0.85, putting it at +2.35 and putting Src3's value at about -2.35.
    If '100' = 1V, then we want to lower the reference number by 85.

    Note: If one of the sources report Ref Offset Fail, then temporarily ignore that one and calculate the value based on the other sources.

  5. Open the equipment pool (System > Equip > Nodes). Select Pool > Correct 10 MHz. Adjust the value until a source reports a Ref Offset Fail.
  6. From the equipment pool, open the module browser (Pool > Control Modules). Highlight the EPC and select 'Node > EE Save Node Info'. When it asks if you're sure, select 'Yes'.
  7. Do a system startup again (System > Equip > Startup).
  8. From the diagnose window, run a self test again. (Run > Self Test). Confirm what sources do not have a Fail.
  9. If the reference offsets are not centered at 0 (+/-0.5V), then repeat the procedure again.

The system timebase is now verified to be within +/-3 ppm. At the maximum specified aging rate, the system will remain within spec for an additional 10 years.

PrintEmail Link
https://roos.com/docs/RBEH-8YFTL9
ROOS INSTRUMENTS CONFIDENTIAL AND PROPRIETARY
©2012-2023 Roos Instruments, Inc. All rights reserved.