Special Operations; Offset Calibration; Factory Reset - Stanford Research Systems SR446 Operation And Service Manual

400 mhz programmable gain preamplifier

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1.3 Special operations

SR446 400 MHz Programmable Gain Preamplifier

The SR446 has an automatic offset calibration feature that will trim the

input offset voltage to within ± 1 mV of zero after operation. To trim the

DC offset:

1. Ensure the unit has been on for at least 30 minutes to warm up.

2. Disconnect cables from the input and both output ports.

3. Select input grounded by pressing the [Couple] button until

is illuminated.

4. With the

indicator illuminated, press and hold the [Couple]

GND

button until the display shows

5. Release the [Couple] button.

The display will show a countdown while each gain configuration is

separately trimmed and recorded to non‑volatile memory. When the

procedure has completed, the display will briefly show

OCAL command (§2.3.8, pg 19).

Restoring the factory default settings of the SR446 will erase all

user settings and return the instrument to the *RST configuration.

Additionally, any trim data from offset calibration (see section 1.3.1,

above) is erased and returned to the original factory calibration. See

the FRST command (§2.3.8, pg 19).

To initiate a factory reset from the front panel:

1. Turn off the unit.

2. Press and hold the [Couple] button, and then press the [POWER]

button while continuing to hold [Couple] depressed.

3. The display will show

4. After about 5 seconds, the unit will return to normal operation.

cAL .

rSt

GND

End . See the

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