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Lake Shore 625 User Manual

Superconducting magnet power supply
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Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake Shore Cryotronics, Inc. No government
or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary rights of Lake Shore Cryotronics,
Inc. in these developments. Methods and apparatus disclosed herein may be subject to U.S. Patents existing or applied for. Lake Shore Cryotronics, Inc.
reserves the right to add, improve, modify, or withdraw functions, design modifications, or products at any time without notice. Lake Shore shall not be
liable for errors contained herein or for incidental or consequential damages in connection with furnishing, performance, or use of this material.
Revision: 1.6
User's Manual
Model 625
Superconducting
Magnet Power Supply
Lake Shore Cryotronics, Inc.
575 McCorkle Blvd.
Westerville, Ohio 43082-8888 USA
E-mail Addresses:
sales@lakeshore.com
service@lakeshore.com
Visit Our Website At:
www.lakeshore.com
Fax: (614) 891-1392
Telephone: (614) 891-2243
P/N 119-037
9 November 2015

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  • Page 1 Inc. in these developments. Methods and apparatus disclosed herein may be subject to U.S. Patents existing or applied for. Lake Shore Cryotronics, Inc. reserves the right to add, improve, modify, or withdraw functions, design modifications, or products at any time without notice. Lake Shore shall not be liable for errors contained herein or for incidental or consequential damages in connection with furnishing, performance, or use of this material.
  • Page 2 Lake Shore Model 625 Superconducting MPS User’s Manual...
  • Page 3 Warranty Period and the defective Product is shipped freight prepaid back to Lake Shore, Lake Shore will, at its option, either repair or replace the Product (if it is so defective) without charge for parts, service labor or associated customary return shipping cost to the Purchaser.
  • Page 4 FIRMWARE LIMITATIONS Lake Shore has worked to ensure that the Model 625 firmware is as free of errors as possible, and that the results you obtain from the instrument are accurate and reliable. However, as with any computer-based software, the possibility of errors exists.
  • Page 5 Lake Shore Model 625 Superconducting MPS User’s Manual...
  • Page 6 Lake Shore Model 625 Superconducting MPS User’s Manual...
  • Page 7 To qualify for the CE Mark, the Model 625 meets or exceeds the requirements of the European EMC Directive 89/336/EEC as a CLASS A product. A Class A product is allowed to radiate more RF than a Class B product...
  • Page 8 Lake Shore Model 625 Superconducting MPS User’s Manual...

  • Page 9: Table Of Contents

    Lake Shore Model 625 Superconducting MPS User’s Manual TABLE OF CONTENTS Chapter/Paragraph Title Page INTRODUCTION ..............................1-1 GENERAL ..............................1-1 DESCRIPTION ............................1-1 SPECIFICATIONS ............................ 1-4 SAFETY SUMMARY ..........................1-7 SAFETY SYMBOLS ..........................1-7 MAGNET SYSTEM DESIGN ..........................2-1 GENERAL ..............................2-1 SUPERCONDUCTING MATERIALS ......................
  • Page 10 Lake Shore Model 625 Superconducting MPS User’s Manual TABLE OF CONTENTS (Continued) Chapter/Paragraph Title Page KEYPAD DEFINITION ..........................4-2 4.3.1 Key Descriptions ..........................4-2 4.3.2 General Keypad Operation ........................ 4-3 DISPLAY SETUP ............................4-4 4.4.1 Display Mode ............................. 4-4 4.4.2 Display Remote Voltage Sense ......................
  • Page 11 Lake Shore Model 625 Superconducting MPS User’s Manual TABLE OF CONTENTS (Continued) Chapter/Paragraph Title Page 5.1.5 IEEE Interface Example Programs ....................5-15 5.1.5.1 IEEE-488 Interface Board Installation for Visual Basic Program ..........5-15 5.1.5.2 Visual Basic IEEE-488 Interface Program Setup ..............5-17 5.1.5.3...
  • Page 12 Remote Inhibit and Trigger In Operation ...................... 3-6 Persistent Switch Heater Output Connector ....................3-6 Connecting Two Power Supplies In Parallel ....................3-8 Rack Mounting a Model 625 Power Supply ....................3-9 Model 625 Output Current Display ....................... 4-1 Model 625 Magnet Field Display ........................4-2 Model 625 Status System..........................

  • Page 13: Introduction

    Achieving these goals while driving a challenging load, such as a superconducting magnet, requires a unique solution. The Model 625 delivers up to 60 A at a nominal compliance voltage of 5 V, with the supply acting as either a source or a sink in true 4-quadrant operation.
  • Page 14 Ramping can also be initiated by the trigger input. The output compliance voltage of the Model 625 is settable to a value between 0.1 V and 5 V, with a 100 µV resolution. The voltage is an absolute setting, so a 2 V setting will limit the output to greater than –2.0 V and less than +2.0 V.

  • Page 15: Model 625 Front Panel

    The Model 625 includes IEEE-488 and RS-232C interfaces that provide access to operating data, stored parameters, and remote control of all front panel operating functions. In addition, the Model 625 includes a trigger function that is used to start an output current ramp. When the trigger is activated, either by an external trigger or by computer interface command, the power supply will begin ramping to the new setpoint.

  • Page 16: Specifications

    Lake Shore Model 625 Superconducting MPS User’s Manual SPECIFICATIONS Output Type: Bipolar, Four Quadrant, DC Current Source Current Generation: Linear regulation with digital setting and analog control Current Range: ±60 A Compliance Voltage: ±5 V maximum (nominal, both source and sink)
  • Page 17 Lake Shore Model 625 Superconducting MPS User’s Manual Readings Output Current Resolution: 0.1 mA Accuracy: ±1 mA ±0.05% of reading Update Rate: 2.5 readings/s display, 10 readings/s interface Compensated for lead resistance and 25  source resistance Compensation: Output Voltage (at supply terminals) Resolution: 100 µV...
  • Page 18 Lake Shore Model 625 Superconducting MPS User’s Manual Output Voltage Monitor Sensitivity: 1 V = 1 V Accuracy: ±1% of full scale Noise: 1 mV 20  Source Impedance: Connector: Shared 15-pin D-sub Fault Output Type: Relay (closed on fault)

  • Page 19: Safety Summary

    Do not submerge instrument. Clean only with a damp cloth and mild detergent. Exterior only. Moving and Handling Four handles are provided for ease of moving and handling the Model 625. Always use at least two, and if possible four, handles when carrying the unit.
  • Page 20 Lake Shore Model 625 Superconducting MPS User’s Manual This Page Intentionally Left Blank Introduction...

  • Page 21: Magnet System Design

    This chapter provides information on general magnet system design. It is intended to give the user insight into superconducting materials, superconducting magnets, persistent switches, dewars, and cabling issues. For information on how to install the Model 625 please refer to Chapter 3. Instrument operation information is contained in Chapter 4. SUPERCONDUCTING MATERIALS Superconducting materials have a very special property, that when cooled to very low temperatures, they become perfect conductors of electricity.

  • Page 22: Magnet Inductance

    V is the charging voltage, L is the magnet inductance, and di/dt is the rate of change in current. The Model 625 can charge a magnet up to a 5 V rate, although many magnets are not designed to be charged at that rate.

  • Page 23: Maximum Ramp Rate

    0 amps when a quench is detected ensuring that no additional current is being supplied to the diodes. The Model 625 offers both internal quench detection and a remote inhibit line that can be connected to an external quench detection circuit.

  • Page 24: Magnet Current Leads

    Lake Shore Model 625 Superconducting MPS User’s Manual MAGNET CURRENT LEADS The power supply should be placed close to the magnet to reduce the length of the lead wires. The resistance of the wires becomes very important when such large currents are being supplied to the magnet. The rate at which a magnet can be charged depends on the voltage that can be supplied across the terminals of the magnet given by the equation V = L (di/dt).

  • Page 25: 2.6 Magnet Quench

    Lake Shore Model 625 Superconducting MPS User’s Manual With the magnet submerged in liquid helium, it will be at a temperature of 4.2 K at atmospheric pressure. Some magnets are rated to work at 2.2 K allowing a larger field to be generated. This temperature can be achieved by lowering the pressure over the helium reservoir thereby lowering the boiling point of the helium.

  • Page 26: Cutaway Of A Typical Helium Dewar, Magnet, And Insert

    Lake Shore Model 625 Superconducting MPS User’s Manual Figure 2-2. Cutaway Of A Typical Helium Dewar, Magnet, and Insert Magnet System Design...

  • Page 27: Installation

    Included only when purchased with VAC-120-ALL Power Option. 3.1.1 Moving and Handling Four handles are provided for ease of moving and handling the Model 625. Always use at least two, and if possible four, handles when carrying the unit. Installation...

  • Page 28: Rear Panel Definition

    Lake Shore Model 625 Superconducting MPS User’s Manual REAR PANEL DEFINITION This paragraph defines the rear panel of the Model 625. See Figure 3-1. Readers are referred to paragraphs that contain installation instructions and connector pin-outs for each feature. A summary of connector pin-outs is provided in Paragraph 7.12.

  • Page 29: Line Input Assembly

    Line Fuse and Fuse Holder The line fuse is an important safety feature of the Model 625. If a fuse ever fails, it is important to replace it with the value and type indicated on the rear panel for the line voltage setting. The letter T on the fuse rating indicates that the instrument requires a time-delay or slow-blow fuse.

  • Page 30: Power Switch

    Power Switch The power switch is on the front panel of the Model 625 and turns line power to the instrument On and Off. When the circle is depressed, power is Off. When the line is depressed, power is On.

  • Page 31: Remote Voltage Sense

    Remote Voltage Sense The Model 625 provides a connection for remote voltage sense leads. This connection is normally used to measure the voltage at the magnet allowing a more accurate reading of magnet voltage by eliminating voltage drops in the leads connecting the power supply to the magnet.

  • Page 32: Persistent Switch Heater Output

    Lake Shore Model 625 Superconducting MPS User’s Manual 3.6.2 Remote Inhibit The Remote Inhibit connection on the Digital I/O connector is an input that instructs the power supply to immediately set the output current to 0 A. This input allows an external device to immediately shut off the output current of the supply in case of a failure.

  • Page 33: Instrument Grounding And Isolation

    CONNECTING MULTIPLE UNITS IN PARALLEL Up to two Model 625’s can be connected in parallel to provide up to 120 A of current at a maximum compliance voltage of 5 V. When the units are connected, they are still operated individually. The total amount of current supplied to the load is the sum of the currents that each supply is delivering.

  • Page 34: Connecting Two Power Supplies In Parallel

    Lake Shore Model 625 Superconducting MPS User’s Manual Dual_625_Rear.bmp Figure 3-7. Connecting Two Power Supplies in Parallel Installation...

  • Page 35: 3.10 Rack Mounting

    3.10 RACK MOUNTING The Model 625 can be installed into a 19-inch rack mount cabinet using the included rack mount hardware and 19-inch rack support rails. The power supply comes from the factory with feet installed. These feet need to be removed if the supply is going to be rack mounted.
  • Page 36 Lake Shore Model 625 Superconducting MPS User’s Manual This Page Intentionally Left Blank 3-10 Installation...

  • Page 37: Operation

    When the Model 625 is turned on, the display shows the Lake Shore logo and the alarm beeper sounds briefly. After a few seconds, a “Checking Hardware” message will appear while the instrument does an internal diagnostic and makes sure everything is working before the output is turned on.

  • Page 38: Magnet Field Display

    KEYPAD DEFINITION The Model 625 has 26 keys separated into 4 groups on the instrument front panel. The group of keys farthest to the left control the persistent switch heater, the center group combines instrument setup and data entry, the keys farthest to the right control the computer interface mode of the instrument, and the keys at the bottom control the output current.

  • Page 39: General Keypad Operation

    4.3.2 General Keypad Operation The Model 625 uses three basic keypad operations, direct operation, setting selection and data entry, for the majority of operator interface. A few specialized keypad operations, such as ramp segment entry, are described in the individual operation paragraphs.

  • Page 40: Display Setup

    Display Mode The Model 625 is able to display in two modes, output current mode or magnetic field mode. In output current mode, the output current and voltage are displayed using large 11 × 15 block characters. In magnet field mode, the calculated magnet field is displayed using large 11 ×...

  • Page 41: Display Brightness

    SETTING OUTPUT CURRENT The main purpose of the Model 625 Superconducting Power Supply is to supply a very precise and stable current to a highly inductive load. Before setting output current, make sure that the instrument is properly setup for the magnet system that is being used.

  • Page 42: Current Ramp Rate

    CURRENT RAMP RATE The output current of the Model 625 will always ramp from one current setting to another. There is no way to turn off the current ramping function, but if a very fast ramp rate is desired, a ramp rate as large as 99.999 A/s can be entered to simulate a step change.

  • Page 43: Compliance Voltage Limit

    Lake Shore Model 625 Superconducting MPS User’s Manual COMPLIANCE VOLTAGE LIMIT The output compliance voltage limit of the Model 625 can be set between 0.1 and 5 V. The setting is in magnitude only and will limit both positive and negative voltages.

  • Page 44: Maximum Compliance Voltage Limit

    Lake Shore Model 625 Superconducting MPS User’s Manual To set the maximum output current limit press Max Settings. The first maximum setting screen appears as a prompt for the maximum output current limit. Maximum Settings Enter a Value For Max Current: 60.0000 A Use the data entry keys to enter the maximum output current limit value between 0.0000 and 60.0000 A.

  • Page 45: 4.12 Ramp Segments

    Many magnets cannot be charged or discharged at the same rate throughout its entire current capacity. Typically the magnet cannot be charged as fast when the current in the magnet is high. The Model 625 has a ramp segment feature that can change the output current ramp rate based on the output current setting.

  • Page 46: Field Constant

    In a superconducting magnet, magnetic field is directly proportional to the current in the magnet. Because of this relationship, the Model 625 is able to display a calculated field based on a user entered field constant in units of T/A or kG/A.

  • Page 47: Persistent Switch Heater Output

    Lake Shore Model 625 Superconducting MPS User’s Manual 4.14.1 Persistent Switch Heater Output Enable The persistent switch heater should be enabled only if there is an active persistent switch in the magnet system. If no persistent switch is being used, then the persistent switch heater should be disabled. This will remove the persistent switch heater information from the bottom of the display as well as disable the persistent switch heater on and off buttons.

  • Page 48: Persistent Switch Heater Delay

    While the magnet is in persistent mode, the output current can be ramped at a faster rate since it is not ramping against the inductance of the magnet. The Model 625 includes the persistent mode ramp rate feature that will automatically switch to the faster ramp rate when the magnet is in persistent mode.

  • Page 49: 4.15 Psh On/Off

    If the currents are not equal when the PSH is turned on, there is a possibility that the magnet can quench. The Model 625 adds an extra layer of protection to keep this from happening. The Model 625 stores the output current setting of the supply when the PSH was turned off last.

  • Page 50: Quench Detection

    The formula V = L (di/dt) can be used to calculate the maximum ramp rate. For example, the Model 625 has a maximum compliance voltage of 5 V, so for a 10 H magnet, the maximum ramp rate that is possible is 5/10 or 0.5 A/s.

  • Page 51: 4.17 Error Status Display

    4.18 EXTERNAL CURRENT PROGRAMMING The output current of the Model 625 can be set internally, externally, or by the sum of the external and internal settings. Normally, the current is controlled internally by entering a setting from the front panel using the Output Setting key.

  • Page 52: 4.19 Locking The Keypad

    The keypad lock feature prevents accidental changes to parameter values. When the keypad is locked, parameter values may be viewed but cannot be changed from the front panel. The Model 625 has two keypad lock modes. The lock all mode locks out changes to all parameters. The lock limits mode locks out changes to all of the parameters except Output Setting, Ramp Rate, Voltage Limit, Zero Output, Stop Output, Pause Output, PSH On, and PSH Off.

  • Page 53: 4.20 Interface

    4.20 INTERFACE There are two computer interfaces included with the Model 625, a serial interface and an IEEE-488 interface. These interfaces are used to connect the instrument to a computer for automated control or data taking. Refer to Chapter 5.

  • Page 54: 4.21 Default Parameter Values

    Lake Shore Model 625 Superconducting MPS User’s Manual Computer Interface Select With °® IEEE Term: Cr Lf Use the s or t key to select one of the following terminators: CR/LF, LF/CR, LF, and EOI. The default is Cr Lf. Press Enter to accept the new selection and continue to the next setting screen.

  • Page 55: Computer Interface Operation

    Paragraph 7.12.2. Cables can be purchased from Lake Shore or other electronic suppliers. Cable lengths are limited to 2 meters for each device and 20 meters for the entire bus. The Model 625 can drive bus with up to 10 loads. If more instruments or cable length is required, a bus expander must be used.

  • Page 56: Changing Ieee-488 Interface Parameters

    Remote/Local Operation Normal operations from the keypad are referred to as ‘Local’ operations. The Model 625 can also be configured for ‘Remote’ operations via the IEEE-488 interface or the Remote key. The Local key will take the instrument out of ‘Remote’...

  • Page 57: Bus Control Commands

    A Universal Command addresses all devices on the bus. Universal Commands include Uniline and Multiline Commands. A Uniline Command (Message) asserts only a single signal line. The Model 625 recognizes two of these messages from the BUS CONTROLLER: Remote (REN) and Interface Clear (IFC). The Model 625 sends one Uniline Command: Service Request (SRQ).

  • Page 58: Status System

    5.1.4.1 Overview The Model 625 implements a status system compliant to the IEEE 488.2 – 1992 standard. The status system provides a method of recording and reporting instrument information and is typically used to control the Service Request (SRQ) interrupt line. A diagram of the status system is shown in Figure 5-1. The status system is made up of register sets, the Status Byte register and the Service Request Enable register.

  • Page 59: Model 625 Status System

    Lake Shore Model 625 Superconducting MPS User’s Manual Figure 5-1. Model 625 Status System (Sheet 1 of 2) Computer Interface Operation...
  • Page 60 Lake Shore Model 625 Superconducting MPS User’s Manual Figure 5-1. Model 625 Status System (Sheet 2 of 2) Computer Interface Operation...
  • Page 61 Lake Shore Model 625 Superconducting MPS User’s Manual 5.1.4.1.6 Reading Registers Any register in the status system may be read using the appropriate query command. Some registers clear when read, others do not. Refer to Paragraph 5.1.4.1.7. The response to a query will be a decimal value that corresponds to the binary-weighted sum of all bits in the register, see Table 5-1.

  • Page 62: Status Register Sets

    5.1.4.2 Status Register Sets As shown in Figure 5-1, there are five register sets in the status system of the Model 625; Standard Event Status Register, Operation Event Register, Hardware Error Status Register, Operational Error Status Register, and the Persistent Switch Error Register.

  • Page 63: Error Status Register Sets

    5.1.4.3 Error Status Register Sets As shown in Figure 5-1, there are three register sets in the error status system of the Model 625; Hardware Error Status Register, Operational Error Status Register, and the Persistent Switch Error Register. 5.1.4.3.1 Hardware Error Status Register Set The Hardware Error Status Register reports the following instrument hardware error events: DAC processor not responding, output control failure, output over voltage, output over current, low line voltage, temperature fault.

  • Page 64: Operational Error Status Register

    Lake Shore Model 625 Superconducting MPS User’s Manual Figure 5-4. Hardware Error Status Register 5.1.4.3.2 Operational Error Status Register Set The Operational Error Status Register reports the following instrument operational error events: magnet discharging through crowbar, magnet quench detected, remote inhibit detected, temperature high, high line voltage, external current program error, calibration error.

  • Page 65: Psh Error Status Register

    Lake Shore Model 625 Superconducting MPS User’s Manual Figure 5-5. Operational Error Status Register 5.1.4.3.3 Persistent Switch Heater Error Status Register Set The PSH Error Status Register reports the following PSH error events: PSH short, PSH open circuit. Any or all of these events may be reported in the standard event summary bit through the enable register, see Figure 5-2.

  • Page 66: Status Byte And Service Request (Srq)

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.1.4.4 Status Byte and Service Request (SRQ) As shown in Figure 5-1, the Status Byte Register receives the summary bits from the two status register sets and the message available summary bit from the output buffer. The status byte is used to generate a service request (SRQ). The selection of summary bits that will generate an SRQ is controlled by the Service Request Enable Register.

  • Page 67: Status Byte Register And Service Request Enable Register

    Lake Shore Model 625 Superconducting MPS User’s Manual Figure 5-7. Status Byte Register and Service Request Enable Register 5.1.4.4.3 Using Service Request (SRQ) and Serial Poll When a Status Byte summary bit (or MAV bit) is enabled by the Service Request Enable Register and goes from 0 to 1, bit 6 (RQS/MSS) of the status byte will be set.
  • Page 68 The bus controller can, for example, send a query command to the Model 625 and then wait for MAV to set. If the MAV bit has been enabled to initiate an SRQ, the user’s program can direct the bus controller to look for the SRQ leaving the bus available for other use.

  • Page 69: Ieee Interface Example Programs

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.1.5 IEEE Interface Example Programs Two BASIC programs are included to illustrate the IEEE-488 communication functions of the instrument. The first program was written in Visual Basic. Refer to Paragraph 5.1.5.1 for instructions on how to setup the program. The Visual Basic code is provided in Table 5-2.

  • Page 70: Gpib0 Setting Configuration

    Lake Shore Model 625 Superconducting MPS User’s Manual Figure 5-8. GPIB0 Setting Configuration Figure 5-9. DEV 12 Device Template Configuration 5-16 Computer Interface Operation...

  • Page 71: Visual Basic Ieee-488 Interface Program Setup

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.1.5.2 Visual Basic IEEE-488 Interface Program Setup This IEEE-488 interface program works with Visual Basic 6.0 (VB6) on an IBM PC (or compatible) with a Pentium- class processor. A Pentium 90 or higher is recommended, running Windows 95 or better. It assumes your IEEE-488 (GPIB) card is installed and operating correctly (refer to Paragraph 5.1.5.1).
  • Page 72 Lake Shore Model 625 Superconducting MPS User’s Manual Table 5-4. IEEE-488 Interface Program Control Properties Current Name Property New Value Label1 Name lblExitProgram Type “exit” to end program. Caption Label2 Name lblCommand Caption Command Label3 Name lblResponse Caption Response Text1...
  • Page 73 Lake Shore Model 625 Superconducting MPS User’s Manual Table 5-5. Visual Basic IEEE-488 Interface Program Public gSend As Boolean 'Global used for Send button state Private Sub cmdSend_Click() 'Routine to handle Send button press gSend = True 'Set Flag to True...

  • Page 74: Ieee-488 Interface Board Installation For Quick Basic Program

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.1.5.3 IEEE-488 Interface Board Installation for Quick Basic Program This procedure works on an IBM PC (or compatible) running DOS or in a DOS window. This example uses the National Instruments GPIB-PCII/IIA card.

  • Page 75: Typical National Instruments Gpib Configuration From Ibconf.exe

    Lake Shore Model 625 Superconducting MPS User’s Manual IBCONF.EXE.eps Figure 5-10. Typical National Instruments GPIB Configuration from IBCONF.EXE Computer Interface Operation 5-21...
  • Page 76 Lake Shore Model 625 Superconducting MPS User’s Manual Table 5-6. Quick Basic IEEE-488 Interface Program IEEEEXAM.BAS EXAMPLE PROGRAM FOR IEEE-488 INTERFACE This program works with QuickBasic 4.0/4.5 on an IBM PC or compatible. The example requires a properly configured National Instruments GPIB-PC2 card. The REM $INCLUDE statement is necessary along with a correct path to the file QBDECL.BAS.

  • Page 77: Program Operation

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.1.5.5 Program Operation Once either example program is running, try the following commands and observe the response of the instrument. Input from the user is shown in bold and terminators are added by the program. The word [term] indicates the required terminators included with the response.

  • Page 78: Serial Interface Overview

    SERIAL INTERFACE OVERVIEW The serial interface used in the Model 625 is commonly referred to as an RS-232C interface. RS-232C is a standard of the Electronics Industries Association (EIA) that describes one of the most common interfaces between computers and electronic equipment.

  • Page 79: Hardware Support

    Hardware Support The Model 625 interface hardware supports the following features. Asynchronous timing is used for the individual bit data within a character. This timing requires start and stop bits as part of each character so the transmitter and receiver can resynchronized between each character.

  • Page 80: Message Flow Control

    Lake Shore Model 625 Superconducting MPS User’s Manual Message Strings (Continued) A query string is issued by the computer and instructs the instrument to send a response. The query format is: <query mnemonic><?><space><parameter data><terminators>. Query mnemonics are often the same as commands with the addition of a question mark. Parameter data is often unnecessary when sending queries.

  • Page 81: Visual Basic Serial Interface Program Setup

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.2.7.1 Visual Basic Serial Interface Program Setup The serial interface program works with Visual Basic 6.0 (VB6) on an IBM PC (or compatible) with a Pentium-class processor. A Pentium 90 or higher is recommended, running Windows 95 or better, with a serial interface. It uses the COM1 communications port at 9600 Baud.
  • Page 82 Lake Shore Model 625 Superconducting MPS User’s Manual Table 5-8. Serial Interface Program Control Properties Current Name Property New Value Label1 Name lblExitProgram Type “exit” to end program. Caption Label2 Name lblCommand Caption Command Label3 Name lblResponse Caption Response Text1...
  • Page 83 Lake Shore Model 625 Superconducting MPS User’s Manual Table 5-9. Visual Basic Serial Interface Program Public gSend As Boolean 'Global used for Send button state Private Sub cmdSend_Click() 'Routine to handle Send button press gSend = True 'Set Flag to True...

  • Page 84: Quick Basic Serial Interface Program Setup

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.2.7.2 Quick Basic Serial Interface Program Setup The serial interface program listed in Table 5-10 works with QuickBasic 4.0/4.5 or Qbasic on an IBM PC (or compatible) running DOS or in a DOS window with a serial interface. It uses the COM1 communication port at 9600 Baud.

  • Page 85: Program Operation

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.2.7.3 Program Operation Once either example program is running, try the following commands and observe the response of the instrument. Input from the user is shown in bold and terminators are added by the program. The word [term] indicates the required terminators included with the response.

  • Page 86: Command Summary

    Lake Shore Model 625 Superconducting MPS User’s Manual COMMAND SUMMARY This paragraph provides a listing of the IEEE-488 and Serial Interface Commands. A summary of all the commands is provided in Table 5-11. All the commands are detailed in Paragraph 5.3.1, which is presented in alphabetical order.
  • Page 87 Lake Shore Model 625 Superconducting MPS User’s Manual Table 5-11. Command Summary Command Function Page Command Function Page *CLS Clear Interface Cmd ........... 34 OPST Operational Status Query .......... 39 *ESE Event Status Enable Cmd ........... 34 OPSTE Operational Status Enable Cmd ........ 39 *ESE? Event Status Enable Query .........

  • Page 88: Interface Commands (Alphabetical Listing)

    Lake Shore Model 625 Superconducting MPS User’s Manual 5.3.1 Interface Commands (Alphabetical Listing) *CLS Clear Interface Command Input: *CLS[term] Remarks: Clears the bits in the Status Byte Register and Standard Event Status Register and terminates all pending operations. Clears the interface, but not the instrument. The related instrument command is *RST.

  • Page 89: Opc Operation Complete Cmd

    Lake Shore Model 625 Superconducting MPS User’s Manual *OPC Operation Complete Command Input: *OPC[term] Remarks: Used in conjunction with bit 0 (OPC of the Standard Event Status Register. If sent as the last command in a command sequence, bit 0 will be set when the instrument completes the operation that was initiated by the command sequence.

  • Page 90: Tst? Self-Test Query

    *TST?[term] Returned: <status>[term] Format: <status> 0 = No errors found, 1 = Errors found Remarks: The Model 625 reports status based on test done at power up. *WAI Wait-to-Continue Command Input: *WAI[term] Remarks: This command is not supported in the Model 625.

  • Page 91: Erst? Error Status Query

    Lake Shore Model 625 Superconducting MPS User’s Manual ERST? Error Status Query Input: ERST? [term] Returned: <hardware errors>, <operational errors>, <PSH errors> [term] Format: nnn,nnn,nnn Remarks: The integers returned represent the sum of the bit weighting of the error bits. Refer to Paragraph 5.1.4.3 for a list of error bits.

  • Page 92: Ieee Ieee-488 Interface Parameter Cmd

    Lake Shore Model 625 Superconducting MPS User’s Manual IEEE IEEE-488 Interface Parameter Command Input: IEEE <terminator>, <EOI enable>, <address>[term] Format: n,n,nn <terminator> Specifies the terminator. Valid entries: 0 = <CR><LF>,1 = <LF><CR>, 2 = <LF>, 3 = No terminator (must have EOI enabled).

  • Page 93: Lock? Keypad Lock Query

    IEEE Interface Mode Command Input: MODE <mode>[term] Format: <mode> 0 = Local, 1 = Remote, 2 = Remote with local lockout. MODE 2[term] – Places the Model 625 into remote mode with local lockout. Example: MODE? IEEE Interface Mode Query Input: MODE?[term] Returned: <mode>[term]...

  • Page 94: Psh Persistent Switch Heater Cmd

    Lake Shore Model 625 Superconducting MPS User’s Manual Persistent Switch Heater Command Input: PSH <mode> [term] Format: n [term] <mode> Specifies if the persistent switch heater is to be turned on or off: 0 = Heater off, 1 = Heater on, 99 = Heater on overriding output current setting check.

  • Page 95: Qnch? Quench Parameter Query

    Lake Shore Model 625 Superconducting MPS User’s Manual QNCH? Quench Parameter Query Input: QNCH? [term] Returned: <enable>, <rate> [term] Format: n, +n.nnnn (Refer to command for description) RATE Output Current Ramp Rate Setting Command Input: RATE <rate> [term] Format: +n.nnnn <rate>...

  • Page 96: Rdgi? Current Output Reading Query

    Lake Shore Model 625 Superconducting MPS User’s Manual RDGI? Current Output Reading Query Input: RDGI? [term] Returned: <current> [term] Format: ±nn.nnnn <current> Actual measured output current. RDGRV? Remote Voltage Sense Reading Query Input: RDGRV? [term] Returned: <voltage> [term] Format: ±n.nnnn <voltage>...

  • Page 97: Setf Output Field Setting Cmd

    Lake Shore Model 625 Superconducting MPS User’s Manual SETF Output Field Setting Command Input: SETF <field> [term] Format: ±nnn.nnnE±nn Specifies the output field setting: 0.0000 – ±601.000E+03 G or 0.0000 – ±60.1000E+00 T. <field> Remarks: Sets the field value that the output will ramp to at the present ramp rate. The setting entered will be based on the field constant and the field units.

  • Page 98: Trig Trigger Output Setting Cmd

    XPGM <mode>[term] Format: <mode> 0 = Internal, 1 = External, 2 = Sum. XPGM 1[term] – Places the Model 625 into external program mode where the output current is set by Example: an external voltage. XPGM? External Program Mode Query...

  • Page 99: Options And Accessories

    Lake Shore Model 625 Superconducting MPS User’s Manual CHAPTER 6 OPTIONS AND ACCESSORIES GENERAL This chapter provides information on power line configurations and accessories available for the Model 625 MPS. MODELS The list of Model 625 part numbers is provided as follows. Part Number Description Superconducting Magnet Power Supply.
  • Page 100 Lake Shore Model 625 Superconducting MPS User’s Manual Options and Accessories...
  • Page 101 Lake Shore Model 625 Superconducting MPS User’s Manual This Page Intentionally Left Blank Options and Accessories...

  • Page 103: Service

    If it is necessary to return the Model 625 for recalibration, repair or replacement, a Return Authorization (RA) number must be obtained from a factory representative or from the Lake Shore web site. Do not return a product to Lake Shore without an RA number.

  • Page 104: Fuse Drawer

    FUSE DRAWER The Model 625 may be configured for two basic AC power configurations: 100 or 120 VAC and 220 or 240 VAC. Each configuration requires the appropriate fuses and fuse holder. Units produced for use with 100 or 120 VAC have two 0.25 ×...

  • Page 105: Fuse Replacement

    Lake Shore Model 625 Superconducting MPS User’s Manual Line_Input.bmp Figure 7-2. Power Fuse Access FUSE REPLACEMENT Use the following procedure to remove and replace the line fuses. WARNING: To avoid potentially lethal shocks, turn off the power supply and disconnect it from AC power before performing these procedures.
  • Page 106 Lake Shore Model 625 Superconducting MPS User’s Manual The error messages are divided into two groups. Instrument hardware errors are related to the instruments internal circuits. When one of these errors occurs, the output crowbar SCR will be thrown, the Fault LED will be lit and there will be no way to clear the error unless power is cycled.

  • Page 107: Output Source Impedance

    OUTPUT SOURCE IMPEDANCE The current output of the Model 625 has a 25 Ω source impedance, resulting from a 25 Ω resistor across the output terminals. This is necessary to keep the output of the power supply stable into the purely inductive load of a superconducting magnet.

  • Page 108: Handling Electrostatic Discharge Sensitive Components

    Lake Shore Model 625 Superconducting MPS User’s Manual 7.8.2 Handling Electrostatic Discharge Sensitive Components Observe all precautions necessary to prevent damage to ESDS components before attempting installation. Bring the device and everything that contacts it to ground potential by providing a conductive surface and discharge paths. As a minimum, observe these precautions: De-energize or disconnect all power and signal sources and loads used with unit.

  • Page 109: 7.10 Firmware Replacement

    Lake Shore Model 625 Superconducting MPS User’s Manual 7.10 FIRMWARE REPLACEMENT There are two integrated circuits (IC) that may potentially require replacement. See Figure 7-3 for the IC location. • Main Firmware Erasable Programmable Read Only Memory (EPROM) (U22) – Contains the user interface software.

  • Page 110: Location Of Important Internal Components

    Lake Shore Model 625 Superconducting MPS User’s Manual 625 PCB.bmp Figure 7-3. Location Of Important Internal Components Service...

  • Page 111: 7.12 Connector And Cable Definitions

    Lake Shore Model 625 Superconducting MPS User’s Manual 7.12 CONNECTOR AND CABLE DEFINITIONS The ANALOG I/O, PSH OUTPUT, DIGITAL I/O, and RS-232 (DTE), and IEEE-488 INTERFACE connectors are defined in Figures 7-4 thru 7-8. Analog_Output.bmp Name Name Voltage Sense –...

  • Page 112: Digital I/O Connector Details

    Lake Shore Model 625 Superconducting MPS User’s Manual Digital_IO.bmp Name Name Fault Out Common Fault Out Remote Inhibit Common Remote Inhibit Trigger Out Common (not used) Trigger Out (not used) Trigger In Common Trigger In Figure 7-6. DIGITAL I/O Connector Details RS-232_Connector.bmp...

  • Page 113: Serial Interface Cable Wiring

    7 - DTR (tied to 4) 8 - CTS (in) 8 - NC 7 - RTS (out) 9 - NC 9 - NC NOTE: Same as null modem cable design except PC CTS is provided from the Model 625 on DTR. Service 7-11...

  • Page 114: Ieee-488 Interface Connector

    The total length of cable allowed in a system is 2 meters for each device on the bus, or 20 meters maximum. The Model 625 can drive a bus of up to 10 devices. A connector extender is required to use the IEEE-488 Interface and Relay Terminal Block at the same time.

  • Page 115: 7.13 Calibration

    These calibrations are done through the computer interface and the calibration constants are stored in the non-volatile memory in the instrument. There are no trim-pots inside the Model 625 and the cover does not have to be removed to calibrate the instrument. The remaining features of the Model 625 do not require calibration to operate within their specified tolerances.
  • Page 116 Equation 1 This resistor must withstand the full current of the Model 625 and do so with a minimum of heating that can easily change the resistance and therefore the current measurement. At 60 A, this resistor only dissipates 3.6 W. Even so, it is highly recommended to mount the resistor on a heat sink with forced air-cooling to minimize temperature rise.
  • Page 117 Even though small, wiring resistance may allow the voltage across the output terminals of the Model 625 to reach 0.5 V or so at 55 A depending upon length.
  • Page 118 Calibrate Output Current Gain (Continued) Send “CALG 10, 0”. To set the output current gain trim constant to 0. Set the Model 625 output current to +55 A (ramp rate 20 A/s nominal). Wait 30 seconds for settling. Measure the Model 625 actual output voltage at the output terminals and record (V...
  • Page 119 Send “CALCOMP 0” (this is a math computation that takes into account the current that flows through the 25  damping resistor that is across the output of the Model 625. “CALCOMP 0” turns the compensation ON so that the reading reflects only the current going through the load by subtracting the current going through the resistor).
  • Page 120 Verify the gain constant to be 1 ±0.02. Send “CALG 6, gain constant”. 10. Verify the Model 625 remote voltage sense reading to match the measured PSH output voltage within, ±0.0005 V. 11. Send “CALSAVE” to write this calibration to non-volatile memory.
  • Page 121 Get the Model 625 external programming voltage reading and record (V reading NOTE: To get this reading from the Model 625, press and hold the Status key on the front panel until the display goes dark (3 seconds). When the key is then released, a diagnostics display will be seen.
  • Page 122 Lake Shore Model 625 Superconducting MPS User’s Manual Calibration-Specific Interface Commands (Continued) CALG? Gain Calibration Constant Query CALG? <type>[term] Input: Format: nn 1 – 10. <type> Returned: <value>[term] Format: ±nnnnnnn (Refer to command for description) CALSAVE Calibration Save Command CALSAVE[term]...

  • Page 123: Appendix A - Glossary Of Terminology

    In Lake Shore instruments, the Autotuning algorithm automatically determines the proper settings for Gain (Proportional), Reset (Integral), and Rate (Derivative) by observing the time response of the system upon changes in setpoint.
  • Page 124 To determine, by measurement or comparison with a standard, the correct value of each scale reading on a meter or other device, or the correct value for each setting of a control knob. Carbon-Glass™. A temperature sensing material fabricated from a carbon-impregnated glass matrix used to make the Lake Shore Carbon Glass Resistor (CGR) family of sensors.
  • Page 125 (units). A system in which centimeter-gram-second units are used for electric and magnetic qualities. general purpose interface bus (GPIB). Another term for the IEEE-488 bus. germanium (Ge). A common temperature sensing material fabricated from doped germanium to make the Lake Shore GR family of resistance temperature sensor elements.
  • Page 126 Lake Shore Model 625 Superconducting MPS User’s Manual Kelvin Scale. The Kelvin Thermodynamic Temperature Scale is the basis for all international scales, including the ITS-90. It is fixed at two points: the absolute zero of temperature (0 K), and the triple point of water (273.16 K), the equilibrium temperature that pure water reaches in the presence of ice and its own vapor.
  • Page 127 Resolution should not be confused with accuracy. RhFe. Rhodium-iron. Rhodium alloyed with less than one atomic percent iron is used to make the Lake Shore RF family of sensors. Rhodium-iron is a spin fluctuation alloy which has a significant temperature coefficient of resistance below 20 K where most metals rapidly lose sensitivity.
  • Page 128 Lake Shore Model 625 Superconducting MPS User’s Manual Seebeck effect. The development of a voltage due to differences in temperature between two junctions of dissimilar metals in the same circuit. self-heating. Heating of a device due to dissipation of power resulting from the excitation applied to the device. The output signal from a sensor increases with excitation level, but so does the self-heating and the associated temperature measurement error.
  • Page 129 Lake Shore Model 625 Superconducting MPS User’s Manual APPENDIX B UNITS FOR MAGNETIC PROPERTIES Table B-1. Conversion from CGS to SI Units Gaussian Conversion SI & Quantity Symbol & CGS emu Factor, C Rationalized mks Magnetic flux density, tesla (T), Wb/m...
  • Page 130 Lake Shore Model 625 Superconducting MPS User’s Manual Table B-2. Recommended SI Values for Physical Constants Quantity Symbol Value (SI units) µ Permeability of Vacuum 4 × 10 Speed of Light in Vacuum 2.9979 × 10  Permitivity of Vacuum 8.8542 ×...

  • Page 131: Appendix C - Handling Liquid Helium And Nitrogen

    Use of liquid helium (LHe) and liquid nitrogen (LN ) is often associated with the Model 625 Superconducting MPS. Although not explosive, there are a number of safety considerations to keep in mind in the handling of LHe and LN C2.0 PROPERTIES...

  • Page 132: C4.0 Liquid Helium And Nitrogen Safety Precautions

    Lake Shore Model 625 Superconducting MPS User’s Manual C4.0 LIQUID HELIUM AND NITROGEN SAFETY PRECAUTIONS Transferring LHe and LN and operation of the storage dewar controls should be in accordance with the manufacturer/supplier’s instructions. During this transfer, it is important that all safety precautions written on the storage dewar and recommended by the manufacturer be followed.

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