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Performance Verification
AM700 Audio Measurement Set Service Manual
4–23
15. Press the Menu button, touch Enables, and enable the THD measurement.
Channel 1 and Channel 2 must also both be enabled. Deselect any of the
other enables that may be selected. Press Clear Menu.
16. Check the frequency measurement and THD + N at 3.5 V and 1 kHz for both
Ch A and Ch B in the RT display window. The THD + N reading should be
approximately 0.005%.
17. Set the frequency and amplitude to the values shown in Table 4–5 and check
the amplitude reading in the RT display window.
For inputs greater than 1 mV (–57.8dBu) to10mV (–37.8dBu) the accuracy
with respect to 120 Hz should be within ±1 dB. From greater than 10 mV
(–37.8 dBu) to 1.946 V (_8 dBu), the accuracy with respect to 120 Hz is
±0.1 dB, typically ±0.05 dB from 50 Hz to 10 kHz. For input amplitudes
greater that 1.946 V (+8 dBu) to less than 64 V (+36 dBu) for input
frequency below 20 kHz and to less than 16 V (+26 dBu) for input frequen-
cies from 20 to 80 kHz, the amplitude accuracy with respect to 120 Hz is
±0.15 dB (typically ±0.05 dB from 50 Hz to 10 kHz).
Manually change the Analyzer input range as you change the generator
amplitude at 1 kHz or 120 Hz to verify manual ranging. Otherwise, leave Auto
Range on. The easiest way to manually change the range is to push the Menu
button to display the Analyzer menus. Then touch Input under the Main Menu
pop-up. This puts Input Range controls on the right hand side of the display as
shown in Figure 4–16. If you touch the ✓ Auto graphic, the check mark
disappears, and the max full-scale value of the selected range appears.
For either Ch A or Ch B, if you touch the range value (for example 8.00 dBu), if
becomes highlighted, and the main control knob will then change it in 6 dB
steps. The units can be changed to Volts by pushing the Units button in the key
pad area.