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Keysight/Agilent U1241B - amp output noise measurement

Posted by 91derlust (A) on August 26, 2015 at 03:36:43

Tried using a Keysight/Agilent U1241B True RMS MM to measure output noise at the binding posts of my SET amp.

The U1241B is supposed to be able to measure AC Voltage a range up to 1000 mV with 0.1 resolution per p.3 of the linked datasheet. However, with the source muted; a faint hum from the speakers; the MM set to AC Volts and ranged to mV; and probes at the speaker terminals, the MM reads 0.0. If I increase the volume with music playing, the MM starts reading when the volume is audible, but faint.

This is the method I have used with a cheap generic MM and it works fine - currently 3.0 and 2.9 mV with coarsely nulled filaments and source muted (of course).

Any thoughts regarding what I might be doing wrong?

Edit: just took another look at the datasheet (fine print) included in the user manual and read this in relation to AC Volts measurement "ACV and AC μA/mA/A specifications are true RMS AC coupled, valid from 5% to 100% of range." Something similar is also stated in the linked datasheet. Does this does mean it will only measure from 50 mV to 1000 mV?

Cheers,
91.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

• U1241B Datasheet   (Open in New Window)

Edits: 08/26/15 08/26/15 08/26/15

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