CTS air tightness_CTS instrument calibration rate_How to calibrate a CTS instrument?

What is the role of the CTS instrument calibration rate?

Performance factor: A quantitative parameter used to describe an instrument's ability to distinguish between acceptable and unacceptable parts.

Similar to the AI learning process, the instrument learns to determine the values for "pass" and "fail" products.

For example: The pressure decay of a standard part (non-leaking part) = 10 mBar , and the pressure decay of a standard part + leak hole (simulated leaking part) = 100 mBar. The discrimination between a qualified part and an unqualified part is therefore 90 mBar. Performance factor =  (100-10)/100  = 90% = 90PF.  The larger the value, the more distinct the discrimination.

The most critical discrimination capability is calculated as follows: (pressure decay of the master part + leak orifice − pressure decay of the master part) > 0.3 mBar, then the test is highly reliable. Users only need to check the data under the menu to know the discrimination capability themselves and can then use it with confidence. If the discrimination capability does not reach 0.3 mBar, adjust the test cycle time to achieve the optimal discrimination capability.

The PF in the instrument is only a reference value for users and does not affect the testing capability of the instrument at all. There is more than one method for calculating this PF as described above. It can be extended to two or three methods. The CTS algorithm is linked to the user's judgment criteria; the lower the judgment criteria are set, the lower the calculated PF will be. It is merely a rigid reference value and does not affect anything.

1. Minimum PF  This parameter is designed to prevent customer errors during calibration, such as the leak orifice not being opened or system instability. The instrument can identify these issues and avoid calibration errors.

2. Some customers now understand calibration well enough that they do not need to focus on the exact PF value. As long as the pressure decay difference between a leaking and a non-leaking part is greater than  0.1 ~ 0.3mBar, they can quickly judge whether the instrument is working reliably.

3. This is another area where CTS direct pressure outperforms differential pressure: the CTS sensor can accurately measure pressure decay and can detect very large pressure drops, an important capability that differential pressure machines do not have.

The CTS algorithm is tied to the user's judgment criteria. The lower the judgment criteria are set, the lower the calculated PF will be.   Then set the instrument's judgment criteria to 4 sccm and calibrate again; at this point the PF should be twice as high.

1. The pressure decay tends to be larger during the first test on a cold machine.

2. The PF calculated by cold machine calibration will be low.

3. Therefore, it is still recommended to first test two or three times under normal working conditions before calibration.