Hello Taho and thank you for the post.
We must be guided by the Do's and Don'ts of the handbook that refer to the maximum permissible operating pressure of the WPS600....... 600 bar, 60 MPa, 8700 psi
Please also be aware the WPS600 is designed specifically for hydraulic fluid and no other liquid or gas.
(I know it can be tempting to try other applications!)
Please also ensure your connection/test hose is rated at 600 bar (minimum) as this too could lead to measurement error, not to mention the safety implication.
I hope this information is of some help, take care.......Steve