Stanford Research Systems SIM914 Operation And Service Manual page 14

2 – 4
1 mA DC current through the resistor. We measure the gain of the
amplifier by measuring the voltage at the output while applying test
current to input. When the gain is properly adjusted, 1 mA applied
to the 50 Ω input generates 50 mV at the input and 500 mV at the
(unterminated) output causing the DMM to indicate a "resistance"
of 500 Ω. (To avoid auto ranging confusion by the DMM, a 453 Ω
resistor is placed in series with the current source.)
Since the DMM uses a DC current as the test source, it is important
that the amplifier offset be nulled prior to performing the DC gain
adjustment.
1. Setup the DMM in the 4-wire resistance measurement mode.
2. Apply the current output to the Channel 1 input via a 453 Ω
in-line resistor.
3. Apply the unterminated Channel 1 output to the DMMs 4-wire
sense input.
4. Adjust P100 (Channel 1 "GAIN" pot) so that the DMM indi-
cates a "resistance" of 500 Ω.
5. Verify that the offset was nulled by connecting the current
source from the DMM to the input of the other channel and
measuring a resistance of less than 1 Ω.
6. Repeat the gain adjustment for Channel 2 by adjusting P200.
Calibration
SIM914 350 MHz Preamplifier