Stanford Research Systems SIM954 Operation And Service Manual page 48

4 – 2 Calibration
Step 3: The trim procedure starts by connecting a mV-meter to the
input of channel 2. The input o set voltage is then trimmed to 0 mV
with R121.
Step 4: After connecting the mV-meter to the output of channel 2, the
output o set voltage can be trimmed to 0 mV with R199.
Iteration: Steps 3 and 4 are repeated as many times as necessary to
trim both input and output o set voltage simultaneously to near 0 mV.
SIM954 300 MHz Dual Inverting Driver Amplifier