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The Hydrostatic Leveling System (HLS) is a reliable and controlled method for monitoring heights, pitches, and rolls of girders. This system utilizes hydrostatic pressure and various sensors for accurate measurements. The integration of HLS with the Undulator provides absolute measurements, calibration, and controlled monitoring. This presentation provides an introduction to HLS, its principle, types of sensors, configuration, and its integration with the Undulator.
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HLS Monitoring System Georg Gassner, SLAC / METOctober 21, 2005 • HLS Introduction • HLS Principle • Types of Sensors • Integration of HLS with the Undulator 1
Hydrostatic Leveling System Introduction The free surfaces of bodies of water have been used for several thousand years as a vertical reference. The proposed Hydrostatic Level Systems (HLS) has several significant advantages over optical methods in determining height differences between two points. Some of these advantages are: • No direct line of sight needs to exist • Not affected by optical refraction • Higher accuracy • Fully automated • Self calibrating • Equipotential surface is the reference 2
Motion of Earth Surface The disadvantage of using the equipotential surface as a reference is that the earth surface itself is not stable but in constant motion. • Earth tides due to sun and moon • Are up to 30mm for a 123 m long Undulator • Can be modeled • Ocean tide loading and atmospheric loading • Can reach up to 30 mm • Can not be modeled 3
HLS Principle Hydrostatic Leveling Systems are based on the principle of communicating vessels or more precisely on the equilibrium of the pressure of the fluid in the communicating vessels. This is mathematically described by the Bernoulli equation. p + r g Z = const. Dp = 0.10 hPa => DZ = 1.02 mm DTemp = 1°C; Z = 100 mm => DZ = 67 mm 4
HLS Configuration There are two principle configurations: • Full filled pipe system • Faster damping time <2 min • Easier installation • Half filled pipe system • Temperature differences do not affect the measurements • Damping time ~10 min 5
Types of Sensors - Capacitive Sensor • Principle Measures the Capacity C of the System • Attributes • Proven to work for many years • Inexpensive • Precision < 1 mm • Accuracy (10 mm range) < 5 mm • Possibly affected by drift • Absolute height measurements are only indirectly achievable 6
Types of Sensors - Ultrasound Sensor • Principle Measures the runtime of an ultrasound pulse • Attributes • No drift (self calibrating) • Precision < 0.1 mm • Accuracy (10 mm range) < 3 mm • Absolute Measurements • More expensive • No long-term experience (10 years) 7
HLS measurements related to the Girder • Any three HLS sensors provide independent monitoring of • Height of the girder • Roll of the girder • Pitch of the girder • The fourth sensor provides a controlled measurement 8
Integration of HLS with the Undulator • Three capacitive sensors per girder • reliable determination of height, roll and pitch • One ultrasonic sensor per girder • Absolute measurements • Calibration of the system • Controlled measurements • 2 inch stainless steel pipes to connect the pots for optimal damping and maintenance • All sensors are connected with TCP/IP (IEEE 802.3af) • Following a standard (off the shelf products) • Power supply included • Each sensor communicates independently from all others 9
Conclusion • Reliable and controlled method for monitoring • heights of the girders (1 mm level small range) • pitches of the girders (0.5 mrad) • rolls of the girders (2 mrad) • Damping within 10 min • Supplies Wire Positioning System with information to determine the sag 10
