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CRYOMAGNETICS LM-500 Operating Instructions Manual

Cryogenic liquid level monitor
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OPERATING INSTRUCTION MANUAL
FOR THE
MODEL LM-500
CRYOGENIC LIQUID
LEVEL MONITOR
! " # $%
& '
! " $ #
Web: http://www.cryomagnetics.com
WARNING!
DO NOT ATTEMPT TO OPERATE THIS EQUIPMENT BEFORE YOU
HAVE THOROUGHLY READ THIS INSTRUCTION MANUAL.
LM-500 Rev 1.0.doc

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  • Page 1 OPERATING INSTRUCTION MANUAL FOR THE MODEL LM-500 CRYOGENIC LIQUID LEVEL MONITOR ! " # $% & ' ! " $ # Web: http://www.cryomagnetics.com WARNING! DO NOT ATTEMPT TO OPERATE THIS EQUIPMENT BEFORE YOU HAVE THOROUGHLY READ THIS INSTRUCTION MANUAL. LM-500 Rev 1.0.doc...
  • Page 3 MANUFACTURER'S DECLARATION OF CONFORMITY According to lSO / IEC Guide 22 and EN45014 Manufacturer's Name: Cryomagnetics, Inc. Manufacturer's Address: 1006 Alvin Weinberg Drive Oak Ridge, TN 37830 Declares. the product Product Name: Liquid Cryogen Level Monitor Model Number: LM-500 Product Options:...

  • Page 5: Table Of Contents

    TABLE OF CONTENTS Introduction ..........................1 Factory Calibrations, Installed Options and Certification ............3 Setup ............................5 Line Voltage and Fuse ......................5 Connecting Sensors......................6 LHe Sensor Calibration ......................8 LN 2 Sensor Calibration ......................9 Factory Calibration ......................10 3.5.1 Factory Calibration of a Liquid Helium Channel............
  • Page 6 Theory of Operation........................ 27 Liquid Helium Level Sensing (Superconductive Filament Probes) ........27 Liquid Nitrogen Level Sensing (Capacitive Probes) ............28 LM-500 Circuit Description....................28 Limited Warranty Policy ......................31 Appendix A Computer Interface Command Reference ..............33 Appendix B...

  • Page 7: Introduction

    LM-500 can monitor many manufacturer's capacitive sensors due to advanced circuit design. The LM-500 has user-adjustable high and low setpoints that may be used to control automated refill cycles. With the 2-Sensor option, independent setpoints can be adjusted for each channel. This allows simultaneous control of two liquid cryogen systems with a single LM-500.
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  • Page 9: Factory Calibrations, Installed Options And Certification

    Sensor Manufacturer / Serial No: Sensor Length: Characteristic Resistance/Voltage: Lead Resistance: Control Output: TTL: Open Collector: _______ Other: Analog Output (Option 1): Not Installed: Type: 0-1 Volt: 4-20mA: Computer Interface Installed: RS-232: IEEE-488.2 (Option 2): Notes: Certified: Date: Cryomagnetics Model LM-500 Operating Instruction Manual...
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  • Page 11: Setup

    Also remove the screws on the RS-232 and Sensor(s)/IO connectors. The rear panel can then be pulled back and the cover of the LM-500 can be slid off. Figure 3.0 indicates the changes in circuit board jumpers inside the unit used to make a change in line voltage.

  • Page 12: Connecting Sensors

    The fuse for the LM-500 is mounted on the main circuit board inside the unit. Should the fuse need to be changed, open the LM-500 as described above. Locate the fuse - it is a cylindrical device labeled F1 and can be found on the right side of the unit near the main transformer. Replace the fuse only with another fuse of the same type.
  • Page 13 2 lead wires, the I- and V- leads are combined into a single black lead and the V+ lead is not used. The V+ connection at the input to the LM-500 should be connected to the I+ terminal in this case.

  • Page 14: Lhe Sensor Calibration

    Calibration can not be performed through the LM-500 computer interfaces. To calibrate a sensor, power ON the LM-500 (the sensor does not need to be connected). If the 2- sensor option is installed, use the UP or DOWN arrow keys to highlight the sensor channel to be calibrated and press the MENU key.

  • Page 15: Ln 2 Sensor Calibration

    LM-500. Calibration can not be performed through the LM-500 computer interfaces. To calibrate a sensor, power ON the LM-500 (the sensor does not need to be connected). If the 2- sensor option is installed, use the UP or DOWN arrow keys to highlight the sensor channel to be calibrated and press the MENU key.

  • Page 16: Factory Calibration

    "Zero" setting needs to be corrected. This may be done selecting "Zero" using the UP, DOWN, and Enter keys. The LM-500 will indicate ”Zero Point Cal” on the first line of the display, and "Measure Adjust" options on the second line. If the sensor is connected and the LN2 is near empty, select Measure to automatically measure and reset the zero point.

  • Page 17: Factory Calibration Of A Liquid Helium Channel

    Select the appropriate sensor channel using the up or down arrow keys and press ENTER. The value of the LM-500’s internal current sense resistor will be displayed. The value should not need to be changed. Press ENTER to accept the value of the current sense resistor.

  • Page 18: Factory Calibration Of A Liquid Nitrogen Channel

    When the channel is selected from the factory calibration menu and ENTER is pressed the value of the LM-500’s internal current sense resistor will be displayed. The value should not need to be changed. Press ENTER to accept the value of the current sense resistor.

  • Page 19: Factory Calibration Of The Analog Output Option

    Attach Sensor in LN2 <Enter> when ready Ignore this message (since the sensor is already attached). Press ENTER. The LM-500 will take a final reading, which completes the calibration. The LN2 level used to calibrate the sensor should be measured carefully to avoid errors. Preferably, the level should be at or near the top of the sensor.
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  • Page 21: Operation And Menus

    If your LM-500 is configured for dual sensor inputs, the first line of the display will indicate Sensor #1 and the second line will indicate Sensor #2. If your LM-500 is configured for a single sensor input, the display will only indicate one level.

  • Page 22: Liquid Helium Level Monitor Menu Options

    4.1.2 Limits The LM-500 has an internal audible alarm that can be set to activate when the liquid helium falls below a user-settable threshold. It also has an external “auto-refill” signal that can be used to automatically maintain liquid helium level between high and low limits (using the appropriate transfer hardware).

  • Page 23: Fill

    LM-500 and is found to be above the alarm level set point. The visual indication can also be removed manually if the user enters the menu system and then exits again. Separate indicators are displayed for each channel if the 2-Sensor option is installed.

  • Page 24: Ports

    4.1.7 Ports The Ports menu item allows the user to set the analog output mode of the LM-500 (if this option is installed), select the computer interface which is active (RS-232 or IEEE-488.2 - if installed), and to set up the parameters of the computer interface such as baud rate, address, etc. When the Ports menu item is highlighted, the current setting of the analog and computer interfaces are displayed on the second line.

  • Page 25: Liquid Nitrogen Level Monitor Menu Options

    The low and high set points can be used in a similar manner, or they can be used in conjunction with each other to drive an automatic refill system. See section 5.5 for information on interfacing the LM-500 with an automatic liquid nitrogen refill system.

  • Page 26: Units

    4.2.4 Ports The Ports menu item allows the user to set configure the I/O of the LM-500. When the Ports menu item is highlighted, the current setting of the analog and computer interfaces are displayed on the second line. See section 4.1.7 for further information about setting port options.

  • Page 27: 5.0 Interfacing

    5.0 Interfacing The LM-500 comes standard with an RS-232 computer interface. All front panel functions, except calibration functions, may be accessed using the corresponding command string over the RS-232 port. In addition, an IEEE-488.2 port is available as an option. This port conforms to the IEEE- 488.2-1992 standard.

  • Page 28: Ieee-488.2 Computer Interface

    Analog Output An analog output from the LM-500 is available as an option (Option 1). This output can be specified at the time of purchase to be either 4-20mA or 0-1V. If the 4-20 mA option is installed, the signal is found on the LM-500 rear panel DB-15F connector, pins 5 and 6 (see Figure 3.1).

  • Page 29: Automatic Refill

    5.2 shows a typical automatic liquid cryogen refill system. Note that the system consists not only of the LM-500, but also a Line Voltage Controller Module (Option 5), a cryogen transfer line, a solenoid valve, the level sensor, and any additional venting/plumbing needed to handle off-gas.
  • Page 30 LM-500. The control output(s) of the LM-500 may be set to be either “open collector” or “0-5V”. Refer to Section 2.0 of this manual for the factory settings of your particular LM-500. Figure 3.1 indicates the output pins designated to carry the Control Output signals, and Figure 5.3 indicates the jumper...
  • Page 31 4. The control output(s) of the LM-500 may be disabled by setting the low limit(s) to 0.0. 5. The Timeout setting of the LM-500 should be set to a value which the user is confident is beyond the time needed for a worst-case cryogen transfer, but no further. Should the Cryogen Storage Dewar run out of liquid during a refill cycle, this feature will stop the transfer rather than let it run all night long blowing warm gas into the Cryostat.
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  • Page 33: Theory Of Operation

    Liquid Helium Level Sensing (Superconductive Filament Probes) If at least one input of the LM-500 is configured for liquid helium level sensors, the unit may be used with 2, 3 or 4 wire superconductive filament level sensors for monitoring liquid helium (an industry standard).

  • Page 34: Liquid Nitrogen Level Sensing (Capacitive Probes)

    Liquid Nitrogen Level Sensing (Capacitive Probes) If one or both channels of the LM-500 is configured for capacitive liquid level sensors (such as liquid nitrogen sensors), the unit is configured to provide a supply voltage to the sensor and receive back an analog voltage from the sensor that is proportional to liquid level.
  • Page 35 Due to the flexibility and stability of the LM-500’s circuits, very high resolution and accuracy is achieved. The LM-500’s display is a bright, vacuum fluorescent unit having high contrast. It is capable of full alphanumerics and can clearly be read from a significant distance.
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  • Page 37: Limited Warranty Policy

    This warranty shall be effective for one (1) year after the date of shipment from Cryomagnetics. Cryomagnetics reserves the right to elect to repair, replace, or give credit for the purchase price of any product subject to warranty adjustment. Return of all products for warranty adjustment shall be FOB Oak Ridge, TN, and must have prior authorization for such return from an authorized Cryomagnetics, Inc.
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  • Page 39: Appendix A Computer Interface Command Reference

    Helium Level Sensor are addressed to a Liquid Nitrogen channel, a device dependent error is reported in the ESR, and message "Parameter error" will be returned if error reporting is enabled when using the RS-232 interface. Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 40 The following table lists the LM-500 commands, shows the LM-500 mode and channel where the command may be used, and provides a short command description. Command details are provided in the reference that follows. Command Available Description ALARM Operate Set audible alarm threshold...
  • Page 41 Wait-to Continue Command Command Reference This section describes how each LM-500 command is used and provides a cross-reference to related commands. The command syntax sections show required elements enclosed in <angle brackets> and optional parameters enclosed in [square brackets]. All numbers are decimal (base 10).
  • Page 42 The default channel is set to 1 when power is applied or when the *RST command is sent. Related Commands: ALARM, ALARM?, BOOST, BOOST?, CHAN?, FILL, FILL?, HIGH, HIGH?, INTVL, INTVL?, LNGTH?, LOW, LOW?, MODE, MODE?, MEAS, MEAS?, TYPE?, UNITS, UNITS?, *RST CHAN? Query selected channel Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 43 It is much easier to handle errors under program control when using the RS-232 interface if error messages are disabled, but it is desirable to enable error messages if a terminal program is used to interactively control and query the LM-500. Related Commands: ERROR?
  • Page 44 LOW limit is not set to zero, and if a refill timeout has not occurred. The LM-500 will start sampling the refill channel as in continuous mode until the HIGH limit is exceeded, the timeout set in the FILL menu is exceeded, a *RST command is received, or MENU is selected on the LM-500 front panel.
  • Page 45 Response Range: 0.0 to Sensor Length Description: The LNGTH? query returns the active sensor length in the present units for the selected channel. The length is returned in centimeters if percent is the present unit selection. Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 46 READY bit for the selected channel will be set in the status byte returned by the *STB? command when the measurement is complete. Related Commands: CHAN, CHAN?, MEAS?, *STB? MEAS? Query last completed measurement on selected channel Availability: Operate Mode Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 47 MODE command, the front panel menu, or set to Disabled by the LM-500 if an open sensor was detected. Once the mode is set to Disabled it will remain Disabled until changed by the front panel or the MODE command.
  • Page 48 <Menu Mode> is returned as 1. <Menu Mode> is returned as 0 when in operate mode. Channel detailed status is returned as a decimal number where each bit indicates a status condition of the channel. The meaning of each bit when set to one is shown: Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 49 Related Commands: ALARM, ALARM?, CHAN, CHAN?, HIGH, HIGH?, LNGTH?, LOW, LOW?, MEAS, MEAS?, UNITS? UNITS? Query selected units for selected channel Availability: Operate Mode Command Syntax: UNITS? Parameter Range: CM, IN, PERCENT, or % Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 50 Description: The *ESE? command operates per IEEE Std 488.2-1992 by returning the mask set in the Standard Event Status Enable Register (ESE) by a prior *ESE command. Related Commands: *ESE *ESR? Standard Event Status Register Query Availability: Always Command Syntax: *ESR? Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 51 Availability: Always Command Syntax: *OPC? Description: The *OPC command operates per IEEE Std 488.2-1992 by placing an ASCII character "1" in the output queue since the LM-500 does not defer any commands for later Cryomagnetics Model LM-500 Operating Instruction Manual...
  • Page 52 Command Syntax: *RST Description: The *RST command operates per IEEE Std 488.2-1992 by returning the LM-500 to its power up configuration. This selects channel 1 as the default channel, terminates any refill sequence in progress, and clears any refill timeouts that may have occurred.
  • Page 53 Always Command Syntax: *WAI Description: The *WAI? command operates per IEEE Std 488.2-1992 by accepting the command without generating an error. Since the LM-500 only implements sequential commands the no- operation-pending flag is always TRUE. OPC, *OPC? Related Commands: Cryomagnetics Model LM-500 Operating Instruction Manual...
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  • Page 55: Appendix B Line Voltage Controller Module - Option 5

    Line Voltage Controller Module – Option 5 Overview The Line Voltage Controller Module enables the LM-500 to control one or two 115/230 VAC loads up to 1 Amp each using the LM-500 Low and High setpoints. Section 5.5, Automatic Refill, describes operation of the LM-500 in automatic refill applications.
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