3 Performance Verification for Analog Analyzer
50 Keysight U8903B Service Guide
16 Compare the recorded CMRR values to the specification. If the test fails, adjustment will
need to be carried out accordingly.
Distortion (THD+N) verification
This test verifies if the residual THD+N of the U8903B is within the published specification
using an internal loopback connection to test the THD+N performance.
1 Preset the U8903B audio analyzer. Configure the U8903B generator output channel 1
and 2 to connect to all of its own analyzer input channels (up to 8 channels
concurrently) through internal loopback.
2 Configure the U8903B generator output channels as follows:
– Connection type: Unbalanced
– Output impedance: 600 Ω
– Output grounding configuration: Floating ground
– Waveform: Sine
– Output frequency: 1 kHz
– Output amplitude: 1 Vrms
– Output state: ON
3 Configure the U8903B analyzer input channels to be tested as follows:
– Connection type: Loopback
– Input bandwidth: 90 kHz
– Input coupling: DC
– Input range:1 V
– Voltage detector type: RMS
– Trigger source: Immediate
– Measurement function1: Frequency
– Measurement function2: THD+N Ratio
Table 3-7 Distortion specification
Distortion specification (at 1 kHz, 1 Vrms) Equipment used
≤–108 dB (for 20 Hz to 20 kHz bandwidth, 23 °C ±5 °C)
≤–100 dB (for 20 Hz to 20 kHz bandwidth, 0 °C to 55 °C)
U8903B (internal loopback)
Power on the U8903B audio analyzer for at least 30 minutes before performing the
performance verification.
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