“As modern battery-powered mobile devices and power products become greener and more energy-efficient, engineers urgently need oscilloscopes to provide high-sensitivity small-signal measurement solutions.
As modern battery-powered mobile devices and power products become greener and more energy-efficient, engineers urgently need oscilloscopes to provide high-sensitivity small-signal measurement solutions.
Precautions when using an oscilloscope to probe accessories
If you measure low ripple and low noise in power supplies or power devices, you may use the most sensitive or close to the most sensitive V/div setting of the oscilloscope.
First, try to use a probe with a low attenuation like a 1:1 probe instead of using the standard 10:1 passive probe that comes with the instrument. If a 10:1 probe is used, not only the oscilloscope’s baseline noise floor will increase by 10 times, but the minimum V/div setting of the oscilloscope will also be 10 times larger than when using a 1:1 probe.
Another key technique is that by minimizing the residual noise collected by the probe, the hidden small signals can be detected. General passive probes usually provide 15 cm long ground leads and hook probes in the standard configuration. These two accessories may collect the target signal or noise generated by other nearby devices. Conversely, smaller probes and shorter ground connections, such as the use of a BNC adapter or bayonet ground lead on the circuit board, can significantly reduce the detected noise. The principle is to reduce the inductance by minimizing the number of turns of the connection. load.
Use the N2873A 10:1 probe on channel 1 (yellow) and the N2870A 1:1 probe on channel 3 (blue) to measure a 2 mVpp 100 kHz sine wave
Smaller probes and short ground connections can reduce noise pickup and inductive loads
Improve resolution and reduce random noise
When you measure small signals in a large dynamic range, the measurement resolution you need should be higher than the 8-bit measurement resolution provided by a traditional digital oscilloscope. In addition to using high-resolution digitizers or other measuring instruments, you can also use the built-in high-resolution mode or average mode of the oscilloscope to increase the measurement resolution and reduce random noise. Each acquisition mode has its advantages and disadvantages, depending on different situations.
The average value acquisition mode is suitable for measurement scenarios that meet the following conditions:
‾ Require the maximum bandwidth of the oscilloscope
‾ The signal is repeated
‾ No need for deep memory
‾ Request to control the number of averages
The high-resolution acquisition mode is suitable for measurement scenarios that meet the following conditions:
‾ Does not require the oscilloscope to provide the maximum bandwidth, nor does it require an oscilloscope with a larger sampling rate relative to the bandwidth
‾ The signal must be captured by a single trigger
‾ Requires deep storage to capture longer signal
Properly configuring the oscilloscope can help improve the measurement
If you are focusing on the AC component of the input signal, you may not care about its DC offset. Therefore, you can set the coupling of the oscilloscope to AC mode to remove the DC offset from the input waveform. If the AC component in the signal output is extremely small compared to the DC offset (5 V or 12 V), then you need to set the oscilloscope to DC coupling mode and provide the DC offset through the probe. Active probes such as Keysight InfiniiMax and N2750A InfiniiMode provide a wide offset range that can offset the DC offset in the input signal, allowing the dynamic range to be used more effectively.
Don’t forget that the oscilloscope also provides bandwidth limiting and low-pass filtering functions to make bandwidth more reasonable and effective. Most oscilloscopes have built-in 20 MHz LPF circuits. By limiting the bandwidth of the oscilloscope to a reasonable range, you can further reduce the impact of high-frequency noise in the input signal on the measurement.
Low current measurement
Keysight’s unique measurement solution is designed for wide dynamic range and high sensitivity measurement, which can meet the current difficult current measurement needs. The N2820A/21A AC/DC probe has the highest sensitivity in the industry and can cover a current range from a minimum of 50 uA to a maximum of 5 A.
The N2820A dual-channel high-sensitivity current probe has two built-in parallel differential amplifiers with different gains. Low-gain amplifiers allow you to see the full picture of the waveform (or “zoom out” the waveform view), while high-gain amplifiers provide a “zoomed in” view, allowing you to view extremely small current fluctuations, such as the idle state of a mobile device. The N2820A/21A current probe is ideal for measuring the weak current in the device under test. It can be used to characterize sub-circuits, allowing you to view large signals and details in current waveforms with a wide dynamic range. N2820A/21A current probes are compatible with InﬁniiVision 3000X oscilloscopes, 4000X oscilloscopes and Inﬁniium 9000 series oscilloscopes.
N2820A/21A AC/DC current probe provides the industry’s highest sensitivity and widest dynamic range
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