This page includes notes on restoring lake short communications. Occasionally serial communication with the Lakeshore fails. The first symptom is usually the email warning Unable to read NIRC2 Lakeshore 340 keywords. Also, the showtemps command will yield the following:

waikoko{nirc2eng}30: showtemps
      tdetblck = 29.005 degK
       tgetter = 15.191 degK
      thead2lo = 10.789 degK
       tcamera = 51.322 degK
         tcoll = 50.731 degK
        tbench = 50.815 degK
       tshield = 179.170 degK
        thead1 = 475.000 degK

      Error reading tc_setpa: rdSetpoint (Lakeshore) for control loop 1 on module 1 failed

      Error reading tc_setpb: rdSetpoint (Lakeshore) for control loop 2 on module 1 failed

As long as the block is at 29K and the camera, collimator, bench are at 50K, there is no particular rush (i.e., do not risk observing time), but the communication should be restored as soon as it is possible with adequate staff present.

Although the 340 is critical for NIRC2 cryo control, the serial communication is not. Therefore this is a problem that can typically be addressed when there is sufficient staff on the summit. It is fixed by power cycling the Lakeshore 340. When the problem occurs, typically, the other Lakeshore, the 218, which is a read-only temperature monitor, is still functioning. So, the cryo health can be monitored by watching those temperatures. For example, when the 340 lost serial communication on November 27, 2010, it was possible to compare the collimator temperature with past values:

snaptemps08nov2010a:                         tcoll = 50.588 degK
snaptemps20nov2010a:                         tcoll = 50.575 degK
snaptemps27nov2010a:                         tcoll = 50.627 degK

When NIRC2 is in this failure mode, it is still a good idea to use snaptemps to record temperature values, but be aware that you will see these errors:

Error reading tc_setpa: rdSetpoint (Lakeshore) for control loop 1 on module 1 failed
Error reading tc_setpb: rdSetpoint (Lakeshore) for control loop 2 on module 1 failed
Error reading htrdetblck: rdHeater (Lakeshore) for heater chan 1 on module 1 failed

To restore the 340 comms, cycle power on the Lakeshore 340. The step-by-step procedure is as follows:

NEW PROCEDURES - Power Cycling Lakeshore Remotely:
1. From a waikoko terminal as nirc2eng, type LakeshorePwr cycle (without single quotes).
2. Type showtemps> to confirm that temps are now reporting normally.
OLD MANUAL PROCEDURES (use when the remote procedures above fail):
1. Locate the Lakeshore 340. It resides in the AO electronics vault, in the rack furthest from the door and facing the back wall of the vault (see figure below).
2. To power cycle the Lakehshore 340, use the power switch which is near where the power cord attaches on the back-side of the unit.


NIRC2 rack in the AO electronics vault, where the Lakeshore 340 is located.	Zoom into the Lakeshore 340 display.

For detailed information see the manuals: