Local Lockout; Front Panel Display Test; Display Off Operation; Front Panel Connectors - Stanford Research Systems SR844 User Manual

Local Lockout

The front panel keys and the knob may be disabled by remote interface command (GPIB
or RS-232). Attempts to change the settings from the front panel will display the message
LOCL LOUT indicating that local control is locked out by the remote interface. Note that
the factory preset values leave the front panel keys enabled even during remote operation.
Local/Remote operation is discussed more fully later in this chapter (see the Local key),
and in Chapter 4, Interface Commands.

Front Panel Display Test

To test the front panel displays press Local and Setup together. Some of the front panel
LED's will turn on. Note that the instrument is still operational; only the display is in test
mode. Press +90
the number. Use the knob to move the selected LED's across the panel. Make sure that
every LED can be turned on. Pressing Zero shows a text message on the display. Press
any key other than Phase, +90

Display Off Operation

Enter the Display Test mode as explained above. Press Phase until no LED's are lit. The
SR844 is still operating, output voltages are updated and the unit responds to interface
commands. To change a setting press any key other than Phase ,+90
AuxOut are good choices) to exit the test mode, change the desired parameter, and then
re-enter Display Test mode.

Front Panel Connectors

There are five BNC connectors on the front panel.
SIGNAL
INPUT
CH1
OUTPUT
CH2
OUTPUT
REFERENCE
INPUT
°
to increase the number of illuminated LED's and Phase to decrease
°
, or Zero to exit this test mode.
The measurement range of the SR844 is up to 1 Vrms (+13 dBm), over
the frequency range 25 kHz to 200 MHz. Do not exceed the
damage threshold of
The CH1 output provides a
X or the CH1 displayed quantity.
The CH2 output provides a
Y or the CH2 displayed quantity.
The SR844 accepts sinusoidal and digital signals as external reference
inputs, including low-duty cycle pulse trains. The signal should be a
0 dBm sine wave or a 0.7 to 5 Vpp pulse. The reference input may be
terminated in either 50
± ± ± ±
5V DC+AC.
±
10V analog output proportional to either
±
10V analog output proportional to either
Ω Ω
or 10 k , 40 pF.
SR844 RF Lock-In Amplifier
Overview 3-5
°
or Zero (Local or