## KNOWLEDGEBASE

Item #: 531   |   Created: 4/1/2013
Categories: Oscilloscope - DL1700/1600/1500, Oscilloscope - DL6000/DLM6000, Oscilloscope - DL7400, Oscilloscope - DL9000/SB5000, Oscilloscope - DLM2000

### How Much Residual Noise Should There be on a Yokogawa Oscilloscope?

Solution:

The true noise floor of a Yokogawa oscilloscope is ≤ 2-3mVpp.
The DL9000, for example, has approximately 280uV residual noise at 2mV/Div with input termination set to 50Ω.

The residual noise may be measured by making a Peak-Peak measurement with all cables and probes disconnected, and the V/DIV set to the lowest value. On the display will be a baseline of the internal noise of the scope. This noise occurs after the front-end attenuator circuit. In terms of visually comparing noise, verify these settings on your Yokogawa scope:
• Sampling Mode: RealTime
• Interleave: OFF
• Attenuation: 1:1
• Trigger Mode: Auto
• Interpolation: OFF
• Accumulate: OFF

If the attenuation ratio is not kept at 1:1, the residual noise level is multiplied by whatever attenuation factor you have set. A 10:1 passive probe has a 10:1 attenuation ratio which means that the probe divides the signal by a factor of 10 before it is introduced to the scope. The scope will compensate for this attenuation by multiplying the input signal by a factor of 10. Therefore, if the attenuation ratio is set to 10:1 using a 10:1 probe, you can expect the residual noise level to increase by a factor of 10, i.e. 2mVpp at 1:1 attenuation will be 20mVpp at 10:1 attenuation.

Please keep in mind that the residual noise level will vary with the V/DIV setting. When comparing two scopes, make sure that both scopes have the same setup in terms of attenuation factor and V/DIV.