9
PERFORMANCE TESTS
Performance tests are designed to verify
that the unit is performing within the
specifications.
Necessary Equipment:
1. Lock-In Amplifier
Freq Range 0.1 Hz - 100 kHz
Output Ampl 4 mV rms - 1 Vrms
Output Z 50 Ω
Recommended SRS SR850/830/810
2. 50 ΩTerminator
3. 50 Ω, 20 dB Attenuator
The instructions here apply to SRS DSP
lock-ins (SR850/830/810). Other lock-in
amplifiers may be used. However they will
require substantially longer time constants
to arrive at accurate measurements.
1) Connect the 9-pin power cable from
the rear of the lock-in amplifier to the
SR554. Connect the 20 dB attenuator
to the lock-in reference output and a
BNC cable from that to the SR554
(A) input. Connect another BNC cable
from the SR554's (A) output to the
lock-in’s (A) input. Set SR554 to
buffered mode (X500), (A) input.
2) Power on the lock-in in the default
condition. (SR810/830 Power on
Setup, SR850 Power on Bksp) This
places the lock-in in a known state.
The power LED of the SR554 should
light.
3) Set the input to DC coupled, grounded
shield. Set the time constant to 300
ms (1 s for 1 Hz measurement), 12
dB/oct filter and turn on synchronous
filtering (if available). Set the display
type to magnitude (R) and the
reference sinewave amplitude to 10
mV rms.
4) For each frequency, the following
amplitude should be observed, ± 5%.
Frequency Amplitude
1.0 Hz 31 mV
10 Hz 252 mV
100 Hz 438 mV
200 Hz 442 mV
500 Hz 439 mV
1 kHz 414 mV
10 kHz 96 mV
100 kHz 11 mV
5) Disconnect the lock-in reference from
the SR554 input. Connect the 50 Ω
terminator to the SR554 (A) input.
6) Set the lock-in to measure noise.
7) For each frequency and time constant,
the following rms noise voltage should
be observed (±10%). Set the lock-in
sensitivity to about 5 times the
expected reading and allow it to settle
(10-20 time constants) before making
readings.
Frequency Time Constant Noise Voltage
1.0 Hz 3.0 s 480 nV
10 Hz 1.0 s 260 nV
100 Hz 0.1 s 460 nV
200 Hz 0.1 s 460 nV
500 Hz 0.1 s 460 nV
1 kHz 0.03 s 420 nV
10 kHz 0.03 s 120 nV
100 kHz 0.03 s 60 nV