LC11 Liquid Nitrogen Level Controller User Manual
Contents
1. The following table summarizes the LC11 response to the sensor signals for each alarm mode of Wet Low Level Alarm Mode High Level Alarm Mode Sensors Jumper Installed Jumper Removed 3 Not Filling Not Filling with Alarm Active 2 Either Filling or Waiting Not Filling 1 Filling Either Filling or Waiting 0 Filling with Alarm Active Filling 3 1 The LINE and VALVE Terminals The line terminals LH and LN provide power to the controller and should be connected to the 120VAC 230VAC optional mains This line voltage is also routed to the valve terminals VH and VN when the controller attempts to fill The LN LINE NEUTRAL terminal is directly connected to the VN VALVE NEUTRAL terminal on the LC11 circuit board The LH LINE HOT terminal is connected to the input of the control relay When the relay is closed by the controller the voltage applied to LH appears on VH It is important to correctly connect LH to the hot side of the mains since only this side is switched on an off by the controller 3 2 The 5V and COMMON Terminals The LC11 is equipped with a regulated 5VDC power supply that can be used to power external circuits This makes it particularly easy to add indicators lights buzzers to the controller s STATUS FILLING or ALARM outputs The COMMON terminal is the ground reference OVDC for the power supply Up to 90mA may be drawn from the SVDC terminal and returned via the COMMON terminal The COMMON2. after 23 seconds The LC11 determines if each sensor is wet or dry based on the different thermal conductivities of liquid and gaseous nitrogen This is done by intermittently biasing the sensors with a small amount of heat input If the sensor is submerged in LN the heat is conducted away from the sensor with negligible temperature rise However if the sensor is not submerged a small but measurable temperature rise occurs at the end of the sensor When operated at the temperature of liquid nitrogen the total power dissipated by the three sensors is 132 mW This corresponds to a quiescent boil off rate of 1 liter of LN every 2 weeks The typical latency from when a sensor becomes wet and the corresponding LC11 response is about 10 seconds The typical latency from when a sensor becomes dry and the corresponding LC11 response is 29 seconds The alarm jumper determines how the LC11 responds to the various sensor signals If the jumper is installed the LC11 operates in a low level alarm mode In this mode the alarm output will be activated when all three sensors become dry Filling is initiated when any two sensors become dry Filling is terminated when all three sensors become wet If the alarm jumper is removed the LC11 operates in a high level alarm mode In this mode the alarm output will be activated when all three sensors become wet Filling is initiated when all three sensors become dry and filling is terminated when two sensor become wet
3. f 0 051N SPLASH Ls GUARD tele 0 20 IN FIGURE 3 The LS10 Sensor The LC11 is powered from 120VAC 230VAC optional and is supplied as a circuit board with screw terminals and mounting holes Features of the LC11 include 1 A watch dog timer for high reliability operation 2 A metal oxide varistor MOV to protect the controller from voltage spikes on the power mains 3 an opto isolated zero volt switching relay to prevent electrical noise and 4 A regulated 5VDC power supply that can be used to power external circuits such as lights or buzzers 2 Installation Proper site selection for the LC11 Controller is very important The controller should not be placed where liquid OR COLD VAPOR will fall on it In particular cold exhaust vapors generated during the fill operation must be directed away from the controller The LC11 circuit board has four mounting holes that accommodate 6 bolts The circuit board should not be mounted flush against a conducting surface as this will short out the traces on the bottom of the board A 1 4 inch standoff is recommended when mounting the LC11 board The alarm jumper should be removed if a high alarm function is required Position the LS10 sensors at the desired high low and alarm positions within the LN reservoir For proper operation the sensors must not be permitted to move due to the turbulence generated during the fill operation Sensors should either be anchored in place or shielded from
4. terminal can also be used to ground an external DC supply if one is used with the STATUS FILLING or ALARM outputs 3 3 The STATUS Output The STATUS output indicates if the sensors are installed and operating properly The STATUS signal is an active low open collector output If all three sensors are installed and functioning properly the STATUS output is grounded i e connected to COMMON If the controller determines that any sensor is shorted unplugged or excessively noisy then STATUS flashes between ground and open The number of flashes per second indicates which sensors are faulty one flash per second for sensor 1 two flashes per second for sensor 2 and three flashes per second for sensor 3 See figure 2 for the sensor numbering If two sensors are faulty then every second STATUS will alternately flash for each sensor If all three sensor are faulty then STATUS will flash 4 times per second As shown in figure 4 a simple LED circuit connected between STATUS and 5V can be used to observe the STATUS signal The LED flash patterns for all possible combinations of sensor faults are also shown Pm pe LED FLASH PATTERN ON NONE sasso sn OFE A 1 svoc DAT 2 LED 3 STATUS gt D_M__ 182 150Q 1 amp 3 2 amp 3 ALL e 1 SECH FIGURE 4 Using an LED to observe the STATUS output Alterna
5. waiting state or vice versa If the level is below the low control point shorting TOGGLE to COMMON will disable filling until TOGGLE is released from COMMON Finally if the liquid level is above the high control point or if any sensor is unplugged TOGGLE can be used to override the controller and force fill the reservoir Usually a normally open momentary switch is wired between TOGGLE and COMMON as shown in figure 8 L TOGGLE _ e COMMON o FIGURE 8 A momentary switch can be used to activate the TOGGLE input 4 Specifications Power 120VAC 3Amps 50 60 Hz 230VAC optional Size 3 13 in L x 3 0 in W x 1 5 in H Fill Relay 120VAC 2 5Amps Zero volt switching 230VAC optional Required Sensors LS10 3 each Output Signals STATUS FILLING amp ALARM open collector active low Max Voltage 40VDC relative to COMMON Max Current 150 mA Max Power 350 mW Input Signal TOGGLE active low Output Power Supply 5VDC 90mA max Screw Terminals Accepts 14 to 30 AWG Mounting Holes 2 5 in square pattern 0 15 in I D Specifications are subject to change without notice 5 Warranty The LC11 Level Controller and LS10 Level Sensors are warranted to be free from defects in materials and construction for 1 year from the date of purchase Neither the controller nor sensors contain any user serviceable parts and all warranty repairs must be performed by Teragon Every effort has been made to ensure the accuracy and com
6. K 3 ia EE H O 5VDC d n O DD ALARM JUMPER FIGURE 2 The LC11 circuit board The STATUS output indicates that the sensors are installed and operating properly If all sensors are functioning the STATUS output is connected to COMMON Otherwise the STATUS output flashes between COMMON and open to indicate a fault condition The FILLING output can be used by external equipment to monitor the LC11 s filling status This open collector output is connected to COMMON only when the solid state relay is activated The ALARM output indicates if either a level alarm condition has occurred or if any of the sensors are unplugged shorted or noisy This is also an open collector output that is connected to COMMON when active The TOGGLE input permits external control over the filling process It can be used to change the controllers current state waiting or filling or to override the controller The controller requires three LS10 sensors to monitor the liquid level within the cryogenic reservoir As shown in figure 3 each sensor has a sensing tip that is covered by a splash guard The sensing tip is connected to the sensor plug by a twisted pair of cryoflex leads The 2 5 mm sensor plug mates with the sensor jacks provided on the LC11 circuit board The LS10 Sensors are available with standard lead lengths of 2 3 or 4 feet Noncryogenic sensor extensions are available in 3 6 and 10 foot lengths CRYOFLEX LEADS 25MM PLUG N
7. SUPPLY DEWAR LS10 SENSORSN o FIGURE 1 A typical LC11 application The function of each LS10 Sensor high low or alarm is determined by the sensor s location within the reservoir If the LC11 is configured for a low level alarm the liquid level will be controlled between the middle and upper sensors The alarm function will activate if the lowest sensor becomes dry If the LC11 is configured for a high level alarm the liquid level will be controlled between the middle and lower sensors The alarm function will activate if the highest sensor becomes wet As a safety feature the controller will not initiate or continue a fill operation if any sensor is unplugged As shown in figure 2 the LC11 circuit board is equipped with three jacks that accept the LS10 sensor plugs Screw terminals are used to make all other connections to the LC11 circuit board In addition to the power and valve terminals the controller also has STATUS FILLING and ALARM outputs as well as a TOGGLE input The figure also shows the location of the alarm jumper If the jumper is installed the LC11 operates with a low level alarm function If the jumper is removed the LC11 operates with a high level alarm function gt 120 VAC 2 pa 14 LS10 vave 2 lt JACK 1 DE fi OSE COMMON 4 LS10 TOGGLE JACK 2 STATUS O LS10 FILLING lt JAC
8. TERAGON LCI11 Liquid Nitrogen Level Controller User Manual Teragon Research e 2518 26th Avenue e San Francisco CA 94116 phone 415 664 6814 e fax 415 664 6745 e www trgn com WARNING THE LC11 CONTROLLER CONTAINS CMOS CIRCUITS WHICH ARE SUSCEPTIBLE TO DAMAGE BY ELECTROSTATIC DISCHARGE ESD STANDARD ESD HANDLING PRECAUTIONS SHOULD BE OBSERVED WHEN INSTALLING THE CONTROLLER WARNING TRACES ON THE LC11 CIRCUIT BOARD CAN CARRY LETHAL VOLTAGES INSTALLATION AND MAINTENANCE SHOULD ONLY BE PERFORMED BY A QUALIFIED ELECTRICAL TECHNICIAN WHILE POWER IS APPLIED CONTACT WITH THE CIRCUIT BOARD CAN LEAD TO DAMAGE INJURY OR DEATH WARNING CONTACT WITH LIQUID NITROGEN OR COLD NITROGEN GAS MAY CAUSE SERIOUS FROSTBITE OR BLINDNESS NITROGEN GAS CAN CAUSE RAPID SUFFOCATION USE AND STORE LIQUID NITROGEN ONLY IN WELL VENTILATED PLACES 1 Overview The LC11 Liquid Level Controller uses three LS10 Sensors to monitor and control the liquid nitrogen level in a cryogenic reservoir The controller uses a solid state relay to operate an external cryogenic solenoid valve A typical LC11 application is shown in figure 1 Two of the sensors are used to control the liquid level and the third sensor provides either a high or low level alarm function A jumper on the LC11 circuit board determines which type of alarm the controller uses fil REE TRANSFER 3 VALVE LINE Y E LC11 K CONTROLLER 7 LIQUID NITROGEN
9. ghts switched etc to the appropriate input output terminals Finally connect the unenergized power leads to the LH and LN terminals ensure that the hot leg of the mains power is connected to the LH terminal Apply power to the power leads to begin automated filling of the LN reservoir 3 Operation When power is applied to the LC11 Controller it first runs a diagnostic to determine if all LS10 sensors are installed and functioning properly The controller checks if the sensors are shorted unplugged or excessively noisy Immediately the STATUS signal will indicate if the sensors are operating properly see section 3 3 If both sensors are functioning properly the LC11 begins analyzing their signals to determine if the sensors are wet or dry The first wet dry determinations require 23 seconds from the application of power after which the FILLING amp ALARM outputs are updated and active level control begins If any LS10 sensor is damaged or unplugged the LC11 will cease to control the LN level until the problem is remedied Power will no longer be routed to the VH terminal the FILLING signal will not be active the STATUS signal will indicate which sensors are faulty and the ALARM signal will be activated However the controller can be forced to fill by using the TOGGLE input see section 3 6 Once all the sensor problems are corrected the LC11 will reset itself and rerun the sensor diagnostics Active level control will then resume
10. or output it can be used with external power supplies in excess of SVDC The voltage applied to FILLING should not exceed 40VDC relative to COMMON The current sunk by FILLING should not exceed 150 mA and should not dissipate more than 350 mW 3 5 The ALARM Output The ALARM output indicates if the controller has detected an alarm condition This can result from a low liquid level alarm jumper installed a high liquid level alarm jumper removed or if any sensor is unplugged shorted or excessively noisy The ALARM output is an active low open collector output it is grounded i e connected to COMMON while the alarm condition exists The ALARM signal can be observed using an LED circuit as above or by using an audible siren as shown in figure 7 un IO SIREN PROJECTS UNLIMITED p n Al 550A Ho 5VDC ALARM FIGURE 7 Using a siren to make the ALARM output audible Since ALARM is an open collector output it can be used with external power supplies in excess of 5VDC The voltage applied to ALARM should not exceed 40VDC relative to COMMON The current sunk by ALARM should not exceed 150 mA and should not dissipate more than 350 mW 3 6 The TOGGLE Input The TOGGLE input provides immediate external control over the filling process If the liquid level is between the high and low control points then momentarily shorting the TOGGLE terminal to COMMON will cause the status of the controller to toggle from the filling state to the
11. pleteness of both this manual and the LC11 system that it describes Should you discover any error in either the manual or the LC11 system we would be most grateful to hear from you regarding the oversight Please contact us at tel 415 664 6814 fax 415 664 6745 or e mail sales trgn com We thank you in advance for your assistance The quality of our products and the satisfaction of our customers are our two greatest concerns 2003 Teragon Research Firmware Rev 2 3
12. tely an audible signal can be generated from the STATUS output using either of the circuits in figure 5 The first circuit provides only the audible signal while the second provides both audible and visible signals Note that a transistor is used to invert the STATUS signal so that the buzzer is silent when all sensor are operating properly Since STATUS is an open collector output it can be used with external power supplies in excess of 5VDC The voltage applied to STATUS should not exceed 40VDC relative to COMMON The current sunk by STATUS should not exceed 150 mA and should not dissipate more than 350 mW 5VDC 5VDC ID ma xo ID 2KQ BUZZER A BUZZER LEDW STATUS 2N3904 STATUS 2N3904 1N4148 1N4148 COMMON gt COMMON BUZZER International Comp Corp p n BRT2821P 06 Allied Elect Stock No 623 1931 FIGURE 5 Circuits that generate audible signals from the STATUS output 3 4 The FILLING Output The FILLING output indicates if the controller is trying to fill the reservoir by applying power to the VALVE terminals The FILLING output is an active low open collector output it is grounded i e connected to COMMON while the controller is filling A simple LED circuit connected between FILLING and 5V can be used to observe the FILLING signal as shown in figure 6 svoc L_ gt _ LED FILLING 1500 FIGURE 6 Using an LED to observe the FILLING output Since FILLING is an open collect
13. the turbulence within a shroud or tube Anchoring can be accomplished using a length of stainless rod and nylon cable ties Suitable materials for a shroud or tube include metals PTFE FEP and phenolic Be aware that inserting a warm tube into LN is hazardous liquid will spout from the upper end of the tube due to the boiling that occurs within the tube The LC11 Controller treats all sensors equivalently and any sensor can function as the high low or alarm sensor It is the position of the sensors within the reservoir and the alarm jumper that determine what function each sensor fulfills There is no need to determine which sensor is plugged into which jack Simply place the three sensors at the desired high low and alarm positions within the reservoir and then insert the sensor plugs into any jack on the controller The remaining connections to the LC11 are made using the ten screw terminals on the circuit board The following table gives the names abbreviations and functions for each of the terminals Terminal No Terminal Name Abbreviation Function 1 LINE HOT LH AC Input 2 LINE NEUTRAL LN AC Input 3 VALVE NEUTRAL VN AC Output 4 VALVE HOT VH AC Output 5 COMMON C DC Ground 6 TOGGLE T Logic Input 7 STATUS S Logic Output 8 FILLING F Logic Output 9 ALARM A Logic Output 10 5VDC SV DC Output Connect the solenoid valve leads to the VH and VN terminals Connect any auxiliary circuits li
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