A.Chupyra IWAA10, DESY Hamburg, September 13-17, BINP CAPACITIVE AND ULTRASONIC HYDROSTATIC LEVEL SENSORS A.G. Chupyra, G.A. Gusev, M.N. Kondaurov, A.S. Medvedko, Sh.R. Singatulin BINP, , Novosibirsk, Russia DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, INTRODUCTION. 2.MODIFICATIONS OF CAPACITIVE LEVEL SENSOR: SAS, SASE. 3.MODIFICATIONS OF ULTRASONIC LEVEL SENSORS: ULS, ULSE. 4.COMPARISION OF TWO KINDS OF THE SENSORS. 5.CONCLUSION. 6.REFERENCES. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Introduction Slow ground motion study for future accelerator projects and alignment of large accelerator machine components with high accuracy are important tasks now. One of the prevalent tools for solution of these tasks are Hydrostatic Level Sensors designed to work into the Hydrostatic Levelling System, which is based on principle of communicating vessels. Since 2000 year BINP took part in development and fabrication of Hydrostatic Level Sensors in the network of team-work with FNAL and SLAC. For this time some modifications of capacitive and ultrasonic HLS sensors were developed. During last 9 years more then 300 sensors of both type were fabricated and delivered to FNAL, SLAC, KEK and Montana Tech. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, The biggest delivery of BINP HLS sensors (138 capacitive and 49 ultrasonic) was made at 2008 to SLAC for LCLS project. The sensors were installed by SLAC team on the LCLS Undulator magnet line at the end of Spring 2010: 12 SASE and 12 ULSE were delivered to FNAL for Montana Tech Laboratory, 10 SASE were delivered to KEK. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, MODIFICATIONS OF CAPACITIVE LEVEL SENSOR : SAS, SASE. DESYBINP BINP data acquisition module.Fogale HLS sensor at Aurora mine, March 2000, Illinois.

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP The task was to develop hydrostatic level sensor for slow ground motion study at different sites for NLC project. It was decided to develop capacitive HLS sensor. Capacitive HLS sensor works on principal of capacitance-based sensing. The principal is to create a capacitor, the liquid surface being one electrode, the sensor electrode placed in air medium upper of water surface being the second electrode of capacitor, the capacitance of which is measured in order to derive the distance between these two electrodes. One of disadvantage of existing at that time Fogale HLS sensor was analog representation of output signal. It took to use long multiwire cables for data acquisition and power supply. It was decided that electronics of the developed sensor had to have a built-in microcontroller to provide measurements, initial calculation of signals and interface for digital representation of the measuring data. The RS-485 interface was choose for the data acquisition system.

A.Chupyra IWAA10, DESY Hamburg, September 13-17, A method used for the measurement is to convert variable capacitance into frequency, after that to convert the frequency to digital form. The developed circuit uses the idea presented at the work of N.Toth and Gerard C.M. Meijer [1]. General idea of the converter is an RC-generator with oscillating frequency determined by it’s internal parameters. To connect by turns Cr and Cz one can measure 3 periods T0,T1, T2 and calculate Cz removing parasitic capacitance C. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP T0  11  sec T2 => 11÷18  sec (depending on water level in vessel). The time value of 2 14 periods is measured to determine the all periods. Measurement time for 3 periods is about 1 sec. Frequency of data acquisition is no more 2 Hz. Because measured Cz is normalized with help of reference Cr the all drifts of last one directly influences on measured level value. Temperature coefficient for used Cr is 0±30x10E-6 ℃. Another feature of the capacitive sensor is level noise dependence from measuring level. Greater distance between free water surface and the electrode => less capacitance and worse ratio signal/noise.

A.Chupyra IWAA10, DESY Hamburg, September 13-17, There is also nonlinear dependence of measuring level from capacitance. So each sensor needs in calibration. Linearization with 3-d order polynom is used. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Test system from 4 prototype SAS sensors and 2 Fogale HLS sensors at BINP. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP SAS sensor at Sector 10, SLAC.SAS electrode

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP The capacitive Hydrostatic Level Sensor is a device with two independent parts: Upper part is with electronics; lower part, usually named as vessel, filled with the water. Lower volume was designed in four modifications: a) Vessel-1 with separate outlets for connecting with air tubes and 12 mm water tubes: for the systems with “fully-filled” lower tubes. b) Vessel-2 with 2 outlets of 22 mm diameter for “half-filled” tubes. c) Vessel-3 with 2 outlets of 50 mm diameter for “half-filled” tubes. d) Vessel-4 with one outlet of 33,4 mm diameter for “half-filled” tubes.

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP a)b) c) d)

A.Chupyra IWAA10, DESY Hamburg, September 13-17, The development of last modification of capacitive level sensor was initiated by SLAC for control system of LCLS Undulator magnet line. DESYBINP The electronics of SASE is mounted on two printed circuit boards. The board 1 includes Lantronix XPort [3], Power supply controller, DC-DC converter and transformer. The board 2 includes C=>F converter and flash microcontroller. The board 1 is at the right side, the board 2 is at the left one.

A.Chupyra IWAA10, DESY Hamburg, September 13-17, MODIFICATIONS OF ULTRASONIC LEVEL SENSORS: ULS, ULSE. The development of ultrasonic level sensor also was initiated by SLAC in 2004 for control of LCLS Undulator magnet line. A pulse-echo method is used in ultrasonic HLS for water level measurements. The ultrasonic hydro-location is well known and widely distributed method of distance measurements for many applications. One of precise methods was described by Markus Schlösser and Andreas Herty at their report presented at the 7th IWAA[4]. Their idea is to locate not only the water surface in a vessel, but also two addition surfaces with calibrated distance between them and at the calibrated distance to alignment reference target. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Principle of organizing the reference surfaces at the ULSE (from the M. Schlösser & A. Herty report) H - distance from the water surface Hw to external reference surface (point) Hp DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP Some basic principles of ultrasonic sensor Pulse-echo method for water level measurements: Determine the location of free water surface in a vessel Determine the location of reference reflective surfaces Accurately measuring the time required for a short ultrasonic pulse, generated by a transducer to travel through a thickness of water, to reflect from the free water surface or from the reflective surface, and to be returned to the transducer. The result is expressed by the relation: d is the distance, v is the velocity of sound waves in water, t is the measured round-trip transit time.

8/1/2015A.Chupyra IWAA10, DESY Hamburg, September 13-17, Special transducers => immersion transducers These transducers are designed to operate in a liquid environment. They usually have an impedance matching layer that helps to radiate more sound energy into the water and to receive reflected one. Immersion transducers can be equipped within a planner or focused lens. A focused transducer can improve sensitivity and axial resolution by concentrating the sound energy to a smaller area. The sound that irradiated from a piezoelectric transducer does not originate from a point, but from all the surface of the piezoelectric element. Round transducers are often referred to as piston source transducers because the sound field resembles a mass in front of the transducer. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, For a piston transducer with: Diameter D, Central frequency f, Sound velocity V. Estimation of the near/far zone transition point N. DESYBINP Sound field pictures of the typical piezoelectric transducer

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Near zone => Far zone The ultrasonic beam is more uniform in the far field zone The transition between these zones occurs at a distance N  "natural focus" of a flat (or unfocused) transducer. This near/far distance N is very significant: This area just beyond the near field where the sound wave have maximum strength. Optimal measurement results will be obtained when reflective surfaces are close to N area: N < d < 2N This requirement determines the minimal distance from transducer to target surfaces. DESYBINP

8/1/2015A.Chupyra IWAA10, DESY Hamburg, September 13-17, Parameter \ Transducer Type UnitsV310-RU Panametric H10 KB 3 Krautkraemer H10 KB 3T General Electric (Krautkraemer ) Central frequency f MHz Transducer diameter D mm Beam spread angle α/2 Degree (rad) ( ) (0.0154) (0.022) near/far distance N mm Unfocused immersion transducer parameters Table 1 DESYBINP

8/1/2015A.Chupyra IWAA10, DESY Hamburg, September 13-17, Time: 0.2microsec/div Amplitude: 0.2 V/div Typical time response of V310-RU transducer DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, The goal of the sensor electronics is to measure time intervals with the accuracy as fine as possible and to calculate the resulting values. t1t1 t2t2 t of Transmission Receiving Next transmission Time diagram of one measuring cycle DESYBINP

8/1/2015A.Chupyra IWAA10, DESY Hamburg, September 13-17, Drawings of Krautkraemer and GE (former Krautkraemer) transducers. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP Typical characteristics of GE H10KB3T transducer.

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Real oscillograms of reflected signals. DESYBINP

8/1/2015A. Medvedko27 Ultrasonic HLS prototype with Panametric transducer DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Ultrasonic HLS prototype with Krautkraemer transducer DESYBINP

8/1/2015A. Medvedko29 Last mechanical design of ULSE. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, ULSE for Montana Teach. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, COMPARISION OF TWO KINDS OF THE SENSORS Ultrasonic sensor has a lot of benefits in comparison with capacitive one: more high absolute accuracy more sensitivity at more high sample rate measuring data don’t depend on electronics drifts (temperature and time) because of calibration capability during each measuring cycle no dependence of relation “signal/noise” from measuring level high linearity of transfer coefficient (output signal => level) no need in precise calibration – only accurate measurement of two linear sizes for reference part DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Test of the ULSE and SASE sensors: green line – ULSE level, blue line – SASE level, purple line – level difference. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Noise test of the sensors: green line – ULSE level, blue line – SASE level, purple line – level difference. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, Capacitive level sensors have now only two benefits. 1.Capacitive sensors are more inexpensive. For ultrasonic sensor price of transducer forms considerable part of costs. 2.Capacitive sensors are working during many years. There is a big experience of work with them. Ultrasonic level sensors have not such experience. So very important question! “What is reliability of the ultrasonic transducers? How long they can work without essential worsening of their characteristics?!” => about half of used transdusers of H10KB3 type have failed since end of 2008! New modifications of the transducers with more protected place of cover soldering will be tested. DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, CONCLUSION The future behind Ultrasonic hydrostatic level sensors: Operating experience will grow => about 140 sensors were installed at Desy, more 30 at SLAC, 3 at FNAL and 12 will be installed at South Dacota. The technology of the transducer’s fabrication will be improved The cost in process of growth of manufacture probably will be decreased Next plans: Fabrication of the ultrasonic sensors with last modification of the Krautkraemer transducers for long test measurement => order for the transducers is under progress Upgrade of the sensor electronics for increasing sensitivity at least twice and for improvement of convenience of work => more diagnostics and possibility of interface’s choice by user (Power over Ethernet, RS-485, Canbus). DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, REFERENCES [1]Ferry N. Toth and Gerard C.M. Meijer “A Low-Cost, Smart Capacitive Position Sensor”, / [2]A. Chupyra, M. Kondaurov, A. Medvedko, S. Singatulin, E. Shubin “SAS family of hydrostatic level and tilt sensors for slow ground motion stadies and precise alignment” Proceeding of 8 th IWAA04, Geneve, [3] servers/xport.htmlhttp:// servers/xport.html [4]M. Shlösser, A. Herty, “High precision accelerator alignment of large linear colliders – vertical alignment”. Proceedings of the 7 th IWAA, Spring- 8, [5]A. Chupyra, G. Gusev, M. Kondaurov, A. Medvedko, Sh. Singatulin “The ultrasonic level sensors for precise alignment of particle accelerators and storage rings” Proceeding of 9 th IWAA06, SLAC, [6] A. Chupyra, G. Gusev, M. Kondaurov, A. Medvedko, Sh. Singatulin “The ultrasonic level sensors for precise alignment of particle accelerators and storage rings” Proceeding of 10 th IWAA08, KEK, DESYBINP

A.Chupyra IWAA10, DESY Hamburg, September 13-17, DESYBINP Thank you for attention!