Clock Stopping - Stanford Research Systems SIM918 Operating And Service Manual

2.7 Clock Stopping

2.7 Clock Stopping

SIM918 Precision Current Preamplifier
the SIM900 Mainframe, the autocalibration must also be inside the
mainframe. Otherwise, perform the autocalibration with the same
connection to an independent supply as you use for the operation.
Disconnect all inputs and outputs to the SIM918 while performing the
autocalibration. Connect the center and shield terminals of the Bias BNC
together externally, e.g. with a grounding cap. To calibrate, issue the com-
mand ACAL, or press both [GAIN
on the firmware revision, the calibration may take up to 20 minutes to
complete. During the autocalibration, all LEDs are lit. At the end of
the calibration, the module returns to its pre-ACAL settings, except
the reference clock direction is reset to input.
If autocalibration is unsuccessful, for example because an external
current is applied to Input, the calibration constants revert to their
original values and the command LDDE? will return Code 2. If an
external reference clock is detected, the autocalibration terminates
immediately with LDDE? 2.
Autocalibration does not a ect gain accuracy.
The microprocessor clock of the SIM918 stops if the module is idle,
"freezing" the digital circuitry. The following actions "wake up" the
clock:
1. A power-on.
2. A press of a front-panel button.
3. Activity (send or receive) at the remote interface.
4. An overload.
5. A change in external reference clock status: several rising edges
at the rear-panel connector while in internal clock mode, or
cessation of clocking while in external mode.
6. Loss of PLL lock.
The clock runs for as long as is necessary to complete a change
of settings requested from the front panel, or to communicate the
output of a query through the remote interface. However, the clock
will remain active for as long as the overload or unlocked condition
exists, and for the full duration of an autocalibration.
This default behavior can be modified with the remote com-
mand AWAK. Setting AWAK ON will prevent the clock from stopping.
The module returns to AWAK OFF upon power-on.
] at the same time. Depending
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