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Oxford Instruments ILM200, Руководство оператора

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31

Fnn COMMAND

The FRONT PANEL DISPLAY command sets which channel will be displayed on the
channel 1 display for diagnostic purposes.  The parameters which may be displayed are as
listed for the "R" command above.

Gnnn COMMAND

Allows the needle-valve stepper motor (if fitted) to be set to a new position.  In ILM the
absolute position of the needle valve is not defined, so this command is unlikely to be of
use in normal operation.  It is provided to assist in testing the operation of a needle
valve.

Sn COMMAND

Sets channel n to SLOW sample rate.  (Note that this may be over-ridden by autofill if the
cryogen level is below the FILL threshold and the channel has been configured for
automatic rate switching as described above.

Tn COMMAND

Sets channel n to FAST sample rate and initiates an immediate sample pulse. If automatic
rate switching is active, the rate will revert to SLOW after 15 minutes, if the level is not
rising.

Yn COMMAND

The Y command allows the contents of the RAM memory to be loaded in binary, via the
serial interface.  It is not intended as a user command.  If n is omitted or has the value 2,
only the first 2 kilobytes of the memory are loaded.  If n has the value 8, the entire 8
kilobytes are loaded.  (In general all calibration parameters of interest are held within
the first 2 kB.)   Note that after loading the memory in this way, the new content will be
lost at power-down, unless it has been saved by a STORE sequence as described in section
4.6.

Zn COMMAND

Zn COMMAND

Zn COMMAND

Zn COMMAND

The Z command allows the contents of the RAM memory to be dumped in binary, via the
serial interface.  It is not intended as a user command. Like the Y command, omitting n or
setting it to 2 results in a  2kB dump.  Setting n to 8 gives a full 8kB dump.

8.2

 

Interpreting the Status Message

The status message comprises three separate pieces of information indicating Channel
Usage,  Channel Status and Relay Status as described above.

Channel Usage is given by a single digit for each channel.  Note that this only takes
values in the range 0 to 9 so may be treated as a decimal digit. (However it can equally
well be treated as a hexadecimal digit for consistency with the remaining part of the
status message if you so wish.)

Channel Status is given by a pair of Hexadecimal Digits for each of the three channels.
The pair together are best thought of as representing an 8 bit binary number, where the
bits taken singly or in pairs each have a separate significance

Содержание ILM200

Страница 1: ...vel Meters Issue 1 5 April 2000 File reference ILM 15 DOC Oxford Instruments Superconductivity Tubney Woods Abingdon Oxon OX13 5QX England Tel 44 0 1865 393 200 Fax 44 0 1865 393 333 E mail supercondu...

Страница 2: ...Analogue Outputs 11 3 8 RS232 Serial Data Line Connections 11 3 9 The Oxford Instruments Isobus 12 3 10 GPIB IEEE 488 Connection Optional 12 3 11 The GPIB to ISOBUS Gateway 13 4 Operation 14 4 1 Fron...

Страница 3: ...2 Entering Test Mode 35 9 3 Test t 01 Testing the Display and Relays 35 9 4 Test t 02 Testing the Keys 35 9 5 Test t 03 Setting the GPIB Address 36 9 6 Test t 04 The Diagnostic Front Panel Display 36...

Страница 4: ...It is not intended for use in an inflammable or explosive atmosphere It must not be used under any circumstances for monitoring the level of combustible liquids or in the presence of combustible or ex...

Страница 5: ...f helium and nitrogen channels respectively Thus ILM221 is a three channel instrument with two helium channels and one nitrogen channel From now on we shall use ILM to represent any member of the fami...

Страница 6: ...djusted up to a maximum value of 200 ohms metre There are now two types of wire in use For probes up to 1 4m active length the standard wire is nominally 166 ohms metre and operates at a current of 13...

Страница 7: ...be used in areas where there are flammable or explosive gases or fumes 2 3 Repair and Adjustment Some internal adjustments can be made to ILM Although we do not encourage you to make these adjustments...

Страница 8: ...n the front panel Probes 1 and 2 may be used for either Helium or Nitrogen Probe 3 may only be used for Nitrogen Pin outs used are the same for either probe and no damage will be caused if the wrong t...

Страница 9: ...s the load to absorb the stored energy When the optional internal relays are fitted see below these are connected to the auxiliary port outputs and provide an effective pull up resistance to the 11 vo...

Страница 10: ...ng wires should be brought in via the cable gland on the rear panel After the connections have been made the cover should be replaced before connecting ILM to the mains supply The connections are labe...

Страница 11: ...nds A typical output lead giving analogue outputs in the range 0 to 1V is shown in circuit CNC6802 at the end of this manual Note that no analogue outputs are available if any channel is configured to...

Страница 12: ...ts power from either DTR or RTS signals from the computer To use ISOBUS a special communication protocol is required which is part of the command structure of Oxford Instruments products and is descri...

Страница 13: ...act as a GATEWAY to an ISOBUS cable allowing other instruments to be linked to the GPIB without themselves requiring GPIB interfaces This can enable other Oxford Instruments products for which an int...

Страница 14: ...ows the user to home in on the required value in a logical way A secondary use of RAISE and LOWER is in conjunction with SILENCE to enter the TEST CONFIGURATION mode as described below STATUS Certain...

Страница 15: ...lowing through the probe One two or three display sections may be present on an instrument depending on the number of channels in use If an instrument includes one or more channels which have been con...

Страница 16: ...heat load due to the pulse is negligible Pressing the RATE button switches between FAST and SLOW modes of operation Whenever the channel is switched to the FAST rate a sample is taken straight away Th...

Страница 17: ...for either Helium or Nitrogen probes when the cryostat is still warm since the properties of warm gas are not the same as those of the cold gas which will be present in the reservoir above the liquid...

Страница 18: ...he data has been correctly stored It does not matter which calibration button is pressed the entire calibration of the instrument for all channels will always be saved in a single operation If instead...

Страница 19: ...ge vessel from which the cryogen is to be drawn is empty Taking one of these lines high to 5V will prevent the FILL lamp lighting on that channel The LOW lamp will still light if its threshold is exce...

Страница 20: ...the test 12 parameter to any value other than 0 will result in the needle valve being automatically driven towards the closed position at power up a similar procedure to that employed for the gas flow...

Страница 21: ...sounder is not required it may be switched off by means of switch S2 1 on the main circuit board see section 4 6 5 5 Automatic Shut Down An alternative to sounding an alarm on low cryogen level is to...

Страница 22: ...ge Return Character This may optionally be followed by a Line Feed character The response will normally be sent immediately following the command If a front panel button is pressed when the command is...

Страница 23: ...on ISOBUS an instrument must be able to recognise and respond to commands addressed to it whilst ignoring commands addressed to other instruments This is achieved by starting all commands with a spec...

Страница 24: ...ce since until an address is defined GPIB communication is not possible 6 6 The GPIB Interface The GPIB Interface is an accessory allowing the ILM to be computer controlled by means of the General Pur...

Страница 25: ...command which has been sent whether a reply is to be expected This is fine until something unexpected happens A better alternative is to read a STATUS BYTE from the instrument by conducting a SERIAL...

Страница 26: ...pty power up state It does not reset any of the temperature control functions to the power up state Device Clear may thus be safely used to empty the buffers if these have been filled with a number of...

Страница 27: ...ISOBUS ADDRESSES as described above Note the distinction between the GPIB address which is common to all the instruments on the GATEWAY and their individual ISOBUS addresses which form a part of the m...

Страница 28: ...epresents a decimal digit 0 9 MONITOR COMMANDS always recognised Cn SET CONTROL LOCAL REMOTE LOCK Qn DEFINE COMMUNICATION PROTOCOL Rnn READ PARAMETER nn Unnnnn UNLOCK FOR AND SYSTEM COMMANDS V READ VE...

Страница 29: ...ely disable the front panel controls Qn COMMAND Defines the communication protocol Currently only 2 values of n are significant Q0 Normal Default Value Q2 Sends LF after each CR Note that unlike all o...

Страница 30: ...lt U1 COMMAND UNLOCKED U1234 SLEEP U4321 WAKE UP U9999 Y COMMAND UNLOCKED V COMMAND The VERSION command requires no parameters It returns a message indicating the instrument type and firmware version...

Страница 31: ...tes of the memory are loaded If n has the value 8 the entire 8 kilobytes are loaded In general all calibration parameters of interest are held within the first 2 kB Note that after loading the memory...

Страница 32: ...significance of the three portions of the message Xabc CHANNEL USAGE The three digits correspond to the three channels Allowed values are 0 Channel not in use 1 Channel used for Nitrogen Level 2 Chann...

Страница 33: ...test t 05 as follows Channel 1 166 2 4 32 128 Channel 2 1 Channel 3 0 The configuration number for channel 1 is made up of four elements as indicated corresponding to Pulsed Helium Level operation Aut...

Страница 34: ...or 15 minutes so rate switched to SLOW X210S0C0000R00 Level has fallen below 90 X210S1A0000R10 Level has fallen below 20 FILL threshold Filling has started and Relay 1 is active Rate has automatically...

Страница 35: ...mode from the main test menu select t 00 When SILENCE is pressed normal operation will resume Some tests automatically return to normal operation on completion without returning to the test menu 9 3 T...

Страница 36: ...1 display To restore the correct display re enter test mode and select t 00 Note that when the diagnostic display is in use no channels will show the Err message even if they have no probe connected...

Страница 37: ...96 Light SHUT DOWN Activate Relay 2 112 Light SHUT DOWN Activate Relay 3 Automatic FAST SLOW Switching 0 None Remains in State set by Operator 128 Switches to FAST when FILL first lights Switches to S...

Страница 38: ...cryogen level ILM uses this to establish an approximate default calibration in the absence of cryogen and to ensure that the accurate calibration is within the range of the 0 and 100 adjustments For...

Страница 39: ...econds for a short probe 3 to 4 seconds for a long probe The velocity with which the resistive region propagates down the wire is approximately constant so that a long probe will require a longer puls...

Страница 40: ...ware version 1 04 and later 9 16 Test t 14 Setting Helium Probe Wire Resistivity This test enables the wire resistivity to be set for any channels configured for use with a helium level probe When tes...

Страница 41: ...resetting This may be identified by the He or N2 message reappearing during use The power supply for the analogue circuits is initially regulated by U502 to produce a 45 volt stabilised rail A 12 volt...

Страница 42: ...s The keyboard and display are mapped directly as i o ports on the microprocessor bus and the CPU handles all the display decoding and multiplexing in software Analogue inputs are measured as frequenc...

Страница 43: ...s are present 10 3 3 Three Button Reset If the EEPROM content is completely corrupted of if a new EEPROM has been fitted it will be necessary to carry out a three button reset This completely initiali...

Страница 44: ...lost after Power Down The STORE operation has not been performed after calibrating setting limits etc see section 4 6 No Display or Abnormal Display e g Multiple Decimal Points This probably indicate...

Страница 45: ...BE RESISTANCE Helium 50 200 ohms metre adjustable VOLTAGE COMPLIANCE Helium 40 volts SAMPLING INTERVAL Helium 1 to 1999 seconds FAST 1 to 1999 minutes SLOW PROBE CAPACITANCE Nitrogen 130 pF metre typi...

Страница 46: ...OWER IN IEC 3 pin PROBE INPUT 3 off 9 way D socket AUXILIARY I O 15 way D socket RS232 25 way D socket GPIB Standard Connector if fitted POWER REQUIREMENTS 100 240V 50 60Hz POWER CONSUMPTION 60VA appr...

Страница 47: ...initiated ALARM Lit during alarm state Alarm sounds on entry to alarm state SILENCE Cancels alarm sounder ALARM lamp remains lit until alarm condition is cleared Also used to select functions in TEST...

Страница 48: ...before each character sent X EXamine Status See below for response format Yn Load new content into ILM RAM Use with care wipes all existing calibration See Manual Zn Dump ILM RAM content via interfac...

Страница 49: ...it 0 In Shut Down state Bit 1 Alarm Sounding Relay 4 Active Bit 2 In Alarm State Sound may have been SILENCED Bit 3 Alarm SILENCE prohibited Bit 4 Relay 1 Active Bit 5 Relay 2 Active Bit 6 Relay 3 Act...

Страница 50: ...hing 0 None Remains in State set by Operator 128 Switch to FAST when FILL lights Switch to SLOW when no rise for 15 minutes t 06 Calibrate Internal Current Source ICAL Only available when Test has bee...

Страница 51: ...51 t 12 Set Needle Valve stepper motor operating mode t 13 Set Needle Valve position manually for leak testing t 14 Set wire resistivity ohms metre for helium probes...

Страница 52: ...its accessories Drawing Number No of sheets Description CNC1002 2 sheets DISPLAY BOARD CNC2002 7 sheets MAIN BOARD CNC5102 1 sheet NITROGEN PROBE CNC5202 1 sheet HELIUM PROBE CNC6802 1 sheet 2 CHANNEL...

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