This manual is written for the user of the Liquid Helium Level Detector (LHLD). It is structured in three sections. The first section is an introduction to the LHLD. The second section is a set of instructions explaining how to use the device. The third and final section describes the various warning messages associated with the LHLD. Through out the text various notes and warnings are placed to highlight important information to the reader.

INTRODUCTION:

For the user, the LHLD performs two functions, The first function is chosen when no record of the reading is wanted. The LHLD just reads and displays the amount of helium in the Dewar. The second function is chosen when a record of the amount of helium transferred into or out of the dewar is needed. The level detector makes a record of the liquid level, the date and time of the reading, the users lab, and the users name each time a transfer begins or ends. The user simply tells the level detector when to take the readings.

The LHLD also performs a third function. That is each day at a particular time the liquid level within the Dewar is read and stored in memory. Since this function is completely transparent to the user it will not be discussed in this manual. For more information on this, refer to the LHLD technical manual.

USING THE LHLD:

The choice is now made by the user to take a new reading or to begin a transfer. By pressing the Enter key, the operation, next to the flashing cursor, is chosen. The Left and Right keys will move the cursor between the two choices. The default choice is "Read".

* NOTE. If the LHLD is left for more than 10 seconds on this screen it will return to the screen in Fig 1 and the user will be required to begin again.

If the "READ" choice is made, the LHLD will take a new level reading and the display will return to Screen Fig 1 with the new level and time displayed. However if the "TRANSFER" choice is made the screen shown in Fig.3 is displayed.

The LHLD is now requesting the lab name of the user. To view the list of lab names, the Left and Right keys are used. Pressing the Left key scrolls through the list of lab name backwards and pressing the Right key scrolls through the list forwards. Whenever the desired lab name is displayed press Enter and this name will be selected.

* NOTE: If the LHLD is left for more than 10 seconds on this screen the device will time out and return to the Screen in Fig. 1.

* NOTE: If you do not know your lab name or your labname did not appear in the list see Greg Labbe.

After the selection of a lab name the LHLD displays the screen shown in Fig.4.

The LHLD is now waiting for the selection of a user name. By pressing the Left and Right keys the user is able to scroll through the list of names backwards and forwards respectively. Pressing the Enter key selects the user name displayed on the LCD.

* NOTE: If the LHLD is left for more than 10 seconds on this screen the device will time out and return to screen 1.

* NOTE: The LHLD displays a different list of user names for each lab. Therefore if you do not see your name and you are not sure that the correct lab name was entered do the following. Select any user name and use the "Exit" choice listed below. However if you are sure that the correct labname was chosen and your name is not listed. Select "new" as your user name and see Greg Labbe later.

Once the user name has been selected the LHLD displays the screen shown in Fig. 5.

The LHLD now gives the user the choice to exit the algorithm or to begin a transfer. By pressing the Enter key, the operation next to the flashing cursor is chosen. The Left and Right keys will move the cursor between the two choices. The default choice is "Exit".

* NOTE: If the LHLD is left for more than 10 seconds on this screen it will exit the algorithm and return to the screen in Fig. 1.

* NOTE. If begin transfer is entered and the user was given a "BUFFER FULL" message at the beginning of use, the user should still take a level reading as normal, but report it to Greg Labbe.

If "Exit" is entered the user is returned to the screen in Fig. 1 and must begin the routine again. However if "BGN TRANSFER" is entered the LHLD takes and stores a level reading and displays the screen shown in Fig. 6.

The LHLD now gives the user the choice to take a level reading or to end the transfer. By pressing the Enter key the operation next to the flashing cursor is chosen. The Left and Right keys will move the cursor between the two choices. The default choice is "Read".

Choosing READ at this point simply displays the liquid level on the LCD. The level will remain on the screen for 10 seconds, after which the LHLD redisplays the choice in Fig. 6.

When End transfer is chosen, the LHLD takes an "END" reading and stores it in memory. An acknowledgment is displayed "Transfer Ended" and the LHLD returns to the first screen in the algorithm ( Fig. 1).
 
 

* NOTE: there is no time out for this screen. So be sure that "end transfer" is chosen before returning the Dewar to storage.

* NOTE Cryo users only: If a full warning flashes on the screen, the Dewar is full.

WARNING MESSAGES:

WARNING: If the batteries are not recharged shortly after this message is displayed, all records containing past records could be lost.

The second warning message displayed is the Buffer Full message, This :message will only be displayed after the user first begins to use the LHLD (i.e. between the first two screens) - The message tells the user that there is no more room in memory to store any more level records. Old entries will be overwritten, so the LHLD is still able to take and record level readings. Therefore if the user does a transfer using this dewar they will be able to record the levels as normal. To eliminate this message, the contents of the level detector will need to be downloaded to the host computer. The data is routinely removed every month by Cryogenics, and so the message should rarely if ever be seen.

Table 1 is a summary of the warning messages that a user may encounter. It also gives a short description of what needs to be done to remove the message.