Stanford Research Systems SIM918 Operating And Service Manual page 46

3 – 14
PHAS?
Example:
APLL(?) z
Example:
3.4.6 Calibration commands
ACAL
Example:
Autozero Phase
Query the autozero switch position in the preamplifier. The re-
sponses are ZA 0 (while zeroing the input voltage of the main am-
plifier itself) and ZZ 1 (while zeroing the o set volage of the zeroing
amplifier). These responses alternate with every cycle of the refer-
ence clock.
The switches are parked in the ZA state when autozero is o .
TOKN ON; PHAS?
ZZ
Keep PLL Active
Set (query) the "keep PLL active when autozero is o " mode of
the preamplifier to z
This setting only applies to the external reference clock direction.
When APLL is OFF, turning o the autozero function (CHOP OFF)
will fully halt the PLL oscillator (Section 2.5), ensuring that no digital
clock transitions occur. One consequence of APLL OFF is that the
oscillator will require up to 250 s to reestablish the lock to an external
reference when returning to CHOP ON.
Conversely, with APLL ON the internal oscillator will continue to track
an external 1 pps reference clock during CHOP OFF periods. In this
case, there is no re-lock time needed when returning to CHOP ON.
The PLL oscillator always turns o with CHOP OFF in the internal
reference clock mode.
The APLL setting is retained in non-volatile memory, and is not mod-
ified by a power-on reset.
APLL 1
Autocalibration
Perform a self-calibration (Section 2.6). Make sure to disconnect all
inputs and outputs to the SIM918. Remote commands are not processed
until ACAL is complete.
ACAL
LDDE?
0
checks for success of an autocalibration.
(OFF 0, ON 1) .
SIM918 Precision Current Preamplifier
Remote Operation