EXCELLENCE IN MAGNETICS AND CRYOGENICS MODEL 186 LIQUID LEVEL CONTROLLER INSTALLATION, OPERATION, AND MAINTENANCE INSTRUCTIONS American Magnetics, Inc. PO Box 2509, 112 Flint Road, Oak Ridge, TN 37831-2509, Tel: 423 482-1056, Fax: 423 482-5472 Rev. 3, Dec. 1996 Introduction The American Magnetics, Inc. (AMI) Model 186 Liquid Level Controller system is an advanced, microprocessor-based solution designed to provide accurate and reliable level monitoring and control of virtually any cryogenic liquid. Capacitance-based level sensing The system consists of a Model 186 Liquid Level Controller, sensor, connecting cables, and an optional solenoid-operated fill valve. The instrument sensing element is a 3/8 inch (9.5 mm) OD cylindrical capacitor constructed of stainless steel which allows a cryogenic fluid to become the dielectric between the concentric plates. The instrument measures the sensor capacitance which is directly related to the percentage of the sensor immersed in the cryogenic liquid. The sensors are normally constructed in overall lengths of up to 20 feet (6.1 m). The normal sensor maximum active length is typically 7 inches less than the overall length. Convenient display The instrument is equipped with a 4-digit LED display which provides liquid level indication in inches, centimeters, or percent as selected by a front panel switch. A front panel switch allows the user to adjust the instrument length quickly and easily for a specific active sensor length. The sensor active length can be entered in either inches or centimeters. This length adjustment only effects the display and does not change the calibration of the instrument. Level control The instrument has four level setpoints, two of which are control setpoints used to control liquid level by the solenoid-operated fill valve. The other two set points are alarm setpoints and can be set for other control or alarm functions. Output from this second set of setpoints operates relay contacts in addition to the front panel LED indications. All four setpoints are continuously adjustable from the front panel. The automatic controller (fill) function can be manually overridden or disabled from the front panel. Remote computer monitoring or controlled operation The Model 186 can be provided with an optional 0-10 volt DC signal on the rear panel of the instrument for use with a recorder. A 4-20 mA current loop option is available in lieu of the voltage signal. Computer interface options, including RS-232/422 Serial Port/Data Logger or IEEE-488, are also available. 1 Introduction 2 Introduction Front Panel Layout 1 2 3 4 5 6 7 ACTIVITY 1 0 0.0 HI LEVEL AMI A B Model 186 FILL LO LEVEL Liquid Level Controller } HI POWER MAX AUTO A SET RAISE INCH ~ B POINTS OFF LO % MIN LENGTH INTERVAL OFF CAL ON SILENCE LOWER CM 8 9 10 11 12 13 14 15 1 Fill indication LED 9 MIN calibration push-button 2 Activity LED 10 Approximate calibration push-button 3 LED display 11 MAX calibration push-button 4 HI level LED 12 Fill toggle switch 5 A level LED (control band 13 Control mode rotary switch upper limit) 6 B level LED (control band 14 Raise/lower toggle switch lower limit) 7 LO level LED 15 Units mode toggle switch 8 Power toggle switch 3 Introduction Rear Panel Layout 1 ON RS-232 AMERICAN MAGNETICS, INC. OAK RIDGE, TN U.S.A. S11 J8 COMMUNICATIONS CONTROLLER OUTPUT INPUT POWER J5 J2 LINE VOLTAGE, 250 VA - 2A MAX 115 VAC 230 VAC (RESISTIVE LOAD) 50-60 Hz (SELECTOR SW. INSIDE) 2 3 4 5 1 Optional RS-232/422 or IEEE-488 4 Controller output receptacle communications port (RS-232 shown) 2 Auxiliary DB-9 connector (see 5 Power cord connector Appendix for pinout) 3 RG-59/U coaxial connector to oscillator unit via the extension cable 4 Introduction Instrument/Sensor System Diagram Model 186 instrument, control valve, and sensor system diagram. 5 Introduction Specifications Instrument Specifications Input line voltage 115/230 or 100/200 VAC – 10% Input line frequency 50-60 Hertz, 1 phase Controller output 250 VA maximum @ 2A max current (resistive load) Readout accuracy 0.1% Dimensions 3.8" H x 8.4" W x 11.1" D, Standard 3.475" H x 19" W x 11.1" D, Rack Mount Weight 3.6 lbs. Standard; 4.3 lbs. Rack Mount Operating 15 - 50°C non-condensing environment Analog Output Specifications @ 25°C Integral non-linearity – 0.012% Resolution 16 bits Total error – 0.25% for 4-20 mA output – 0.5% for 0-10 V output Current drift (4-20 mA) 75 ppm/°C Voltage drift (0-10 V) 100 ppm/°C 6 Table of Contents 1 Installation............................................................................................9 2 Calibration..........................................................................................13 Relationship between calibration and sensor length.........................13 Calibration methods..........................................................................13 Variations in the dielectric with changing density...........................15 Open Dewar Calibration................................................................................16 Closed Dewar Calibration..............................................................................16 Presetting the MAX/MIN calibration points....................................17 Closed dewar calibration procedure.................................................18 Approximate Calibration...............................................................................19 3 Operation............................................................................................23 Sensor contamination........................................................................27 4 RS-232 Communication/Data Logger Option.................................29 Serial port connector and cabling.....................................................29 Command/return termination characters..........................................29 Communication DIP Switch Settings............................................................30 Baud rate control...............................................................................30 Data logger output interval...............................................................30 Echo function....................................................................................31 Data logger function.........................................................................31 RS-232 Command Set Reference..................................................................32 Commands for controlling the units of measurement.......................32 Commands for configuring permanent memory...............................33 Commands for querying the configuration.......................................34 Command for returning a level measurement..................................34 Error Codes....................................................................................................35 5 IEEE-488 Communication Option...................................................37 Command/return termination characters..........................................37 Communicating with the Model 186................................................37 Communication DIP Switch Settings............................................................39 IEEE-488 primary bus address.........................................................39 IEEE-488 Command Set Reference..............................................................40 Device clear (DCL) command..........................................................40 Commands for controlling the units of measurement.......................41 Commands for configuring permanent memory...............................42 Commands for querying the configuration.......................................43 Command for returning a level measurement..................................43 7 Table of Contents Error Codes....................................................................................................44 Serial Poll Status Byte...................................................................................45 6 Virtual Instrument Operation..........................................................47 RS-232 Virtual Instrument.............................................................................47 Launching and initializing the RS-232 VI........................................48 Interacting with the running VI........................................................49 IEEE-488 Virtual Instrument.........................................................................50 Launching and initializing the GPIB VI...........................................51 Interacting with the running VI........................................................52 Running multiple GPIB devices.......................................................53 7 Troubleshooting.................................................................................55 LED display not on........................................................................................55 Erratic or erroneous level reading..................................................................56 Controller output does not energize...............................................................57 Unit not responding to communications........................................................57 WARRANTY................................................................................................58 RETURN AUTHORIZATION......................................................................58 Appendix.............................................................................................59 4-20 mA current loop option..........................................................................59 Auxiliary connector J2 pinout........................................................................60 RS-232 cable DB-25 to DB-9 translation......................................................61 Dielectric constants for common liquids.......................................................62 Index....................................................................................................63 8 1 Installation Warning Before energizing the instrument, the earth ground of the power receptacle must be verified to be at earth potential and able to carry the rated current of the power circuit. Using extension cords should be avoided, however, if one must be used, ensure the ground conductor is intact and capable of carrying the rated current. In the event that the ground path of the instrument becomes less than sufficient to carry the rated current of the power circuit, the instrument should be disconnected from power, labeled as unsafe, and removed from place of operation. Do not operate this instrument in the presence of flammable gases. Doing so could result in a life-threatening explosion. Do not modify this instrument in any way. If component replacement is required, return the instrument to AMI facilities as described in the Troubleshooting section of this manual. 1. Unpack the instrument Carefully remove the instrument, sensor, oscillator and interconnecting coaxial cables from the shipping carton and remove all packaging material. A rack mounting kit is supplied if the instrument was purchased with the rack mount option. Note If there is any shipping damage, save all packing material and contact the shipping representative to file a damage claim. Do not return the instrument to AMI unless prior authorization has been received. If the chassis is a table top model, place the instrument on a flat, secure surface. Warning Do not remove the cabinet feet and then reinsert the original screws. Doing so could present a severe life-threatening electrical hazard. If removal of the cabinet feet is desired, replace the original screws with screws not to exceed 1/4" in length. 9