Channels are the number of inputs or the number of waveforms that can be shown simultaneously.
Bandwidth is the frequency an oscilloscope can display. High frequencies are the signal's detail. As the signal frequency increases near the bandwidth limit, the scope cannot amplify the signal and the wave gets smaller on the display. The bandwidth is usually specified as the frequency at which the scope displays the signal at half of its true size. If you want to see all the detail in a signal accurately, there is a rule of thumb: the bandwidth needs to be five times the frequency of the signal you are trying to see! Many competing automotive oscilloscopes only have a bandwidth of between 200kHz and 2MHz and therefore you can only see signals between 40kHz and 400kHz reliably, compared to the PicoScope which can see 4MHz.
20MHz (10MHz on ±50mV Range)
20MHz (10MHz on ±10mV and ±20mV Ranges)
The vertical resolution is the number of bits determine the number of discrete values (dots) that can be displayed vertically on your graph. An 8 bit scope can only display 256 dots resulting in a grainy display. A 12 bit scope can display 4096 dots resulting in a far smoother display and greater accuracy. The extra 4 bits means that for every dot displayed by an 8 bit scope, a 12 bit scope displays 16 dots.
12 bits (4,096 dots)
If a repetitive signal is displayed, the scope's resolution can be enhanced even further. An improvement of up to four bits can be achieved which can increase the resolution of a 12 bit scope to 16 bits. That means that up to 65,536 discrete levels can be displayed yielding an ultra smooth waveform.
16 bits (65,536 dots)
This is the absolute accuracy of a displayed DC level. If you read 10V then, if the accuracy is ±1% then the actual voltage could be any value from 9.9V to 10.1V.
±1% of full scale
±1% of full scale ±300 μV
Sensitivity shows what range of signals the scope can display (at full resolution). There are 10 vertical divisions thus the scope can display signals of 10 times these values (Note: the safe input voltage limit is ±200V). Where appropriate attenuators are used, this range can be increased.
10mV / div to 40V / div
2 mV/div to 10 V/div (10 vertical divisions)
Input Ranges (full scale)
When you use the scope, you can set the vertical scaling in ranges. There is also an auto range that can set the vertical scale for you. The software will warn you if your signal is outside of the range you have selected. Again, appropriate attenuators can extend these ranges and you can define different probes which translate the ranges' scale or unit to suit the quantity being measured (e.g. amps instead of volts).
±50 mV to ±200 V in 12 ranges
±10 mV to ±50 V full scale, in 12 ranges
Input impedance means input resistance. It is important when you are measuring voltages where the source impedance is high. Some sensors have high resistance outputs and a low impedance input can produce an inaccurate measurement. Some scopes have 50Ω inputs and if a sensor with an output of 10V and an impedance of 1kΩ (1000Ω) was to be measured, the value read would be 0.476V, hopelessly inaccurate. The PicoScope with an impedance of 1MΩ (1 million ohms) would measure 9.98V, an error of only 2%. The input capacitance affects high frequency measurements because the impedance of a capacitor decreases as the frequency increases. It is therefore desirable to have a high input impedance and a low input capacitance.
1 MΩ in parallel with 24 pF
1 MΩ ∥ 19 pF
BNC means a special, bayonet connector used to handle high frequencies. Single ended means that only one input is provided per channel and voltages are with reference to its ground. Floating means that each input is separate from the other inputs and the rest of the scope. Each floating input needs its ground to be connected and you can use each channel independently without worrying that the grounds are connected to different places or voltages (up to 30V between channels). Floating inputs also increase reliability because the inputs are separated from the others and the PC. Floating inputs is a very valuable feature that sets the 4425A and 4225A PicoScopes apart from most other scopes.
Floating, single ended, BNC Connectors
Common ground, single ended, BNC Connectors
Input coupling (AC or DC) means that an input can accept DC values or can reject DC so that you can focus on the varying part of the signal. Sometimes a signal has a large DC offset with a small AC signal 'on top'. By selecting AC, the DC offset is removed and you can amplify the AC signal to see it much more clearly.
Software selectable AC/DC
Input Overvoltage Protection
The 4823 is only protected to ±100V. DC voltages in excess of ±100V or AC voltages in excess of 70V may damage the inputs. Always use attenuators when testing inductive devices such as ignition coil primaries, injectors and solenoids.
The absolute maximum voltage that can be applied to an input of the 4425 and 4225 is 250V! Although this is higher than most other automotive scopes can accept, please take note that if you try to measure an AC signal, like 240V mains, the peak value is far higher than 240V - actually 340V - which will damage the scope. The absolute maximum AC sine wave that the 4425 or 4225 scopes can withstand is only 175VAC (provided that there is no DC offset). For safety we recommend that you never apply more than 200V (140VAC) to any input.
±250 V (DC + AC peak)
±100 V (DC + AC peak)
Input Common Mode
This specification is the absolute maximum voltage that can be applied between channel grounds. Channel grounds are not connected together on the 4425A and the 4225A, which means that they must always be connected when measuring. Unlike other scopes, they don't have to be connected to the vehicle ground which allows differential measurments. The voltage from ground to ground on any channel ralative to any other channel must not exceed 30V. The 4823 has common grounds which means that all grounds are electrically connected together. TIP you can use the maths channel feature (i.e. A-B) to do differential measurements, using two channels, to work around this problem.
Buffer memory is the number of dots in the waveform from left to right. If you don’t have enough memory then the waveform won’t show all the detail in the signal. PicoScope has more than enough memory, (250 million samples) so you can zoom in thousands of times and still see a clear display and spot intermittent glitches.
250 M samples shared between active channels
256 MS shared between active channels
The waveform buffer is a memory that collects your most recent waveforms. If a waveform disappears off the screen, you can look back through the waveform buffer to find it.
Up to 10,000 waveforms
When an oscilloscope draws a graph, it draws from left to right. The time taken to fill one of the 10 horizontal divisions is the timebase. A note on time:
millisecond (ms) 1 thousandth of a second
microsecond (μs) 1 millionth of a second
nanosecond (ns) 1 billionth of a second
5 ns/div to 5000 s/div
20 ns/div to 5000 s/div
Maximum Sampling Rate (single shot)
The maximum sampling rate is the maximum number of samples per second depending on the number of channels being used. (MS/s Mega Samples per second)
1 channel in use: 400 MS/s
2 channels in use: 200 MS/s
1 channel in use: 400 MS/s
2 channels in use: 200 MS/s
3 or 4 channels in use: 100 MS/s
80 MS/s (1 to 4 channels in use)
40 MS/s (5 to 8 channels in use)
None: PicoScope acquires waveforms continually, without waiting for an event. Auto: PicoScope waits for a trigger event before capturing data. If there is no trigger event within a reasonable time, it captures data anyway. Repeat: PicoScope waits indefinitely for a trigger event before displaying data. It repeats this process until you click the Stop button. If there is no trigger event, PicoScope displays nothing. Single: PicoScope waits for one occurrence of a trigger event, then stops sampling. To repeat the process, click the Go button. The Single trigger is the only type that allows one capture to fill the entire buffer memory.
None, Auto, Repeat and Single
Rising edge : Trigger when the waveform amplitude increases past a certain set voltage or level. Falling edge : Trigger when the waveform amplitude decreases past a certain set voltage or level. Edge with hysteresis : Hysteresis filters noise. On a rising edge, the waveform must first be below a lower level before rising to the trigger level or the scope will not trigger. The reverse is true on falling edge triggering. Pulse width : Triggering takes place when a specified pulse width is detected. Runt pulse : Triggers if a pulse is found that is too low. Dropout : Triggers when an edge is detected without more edges for a specified time. Finds the end of a train of pulses. Windowed : Triggers when the signal enters or leaves a specified voltage window with specified thresholds. Logic : Triggers when a combination of inputs occurs defined by the operator. Allows more than one input to participate in triggering.
Rising edge, falling edge, edge with hysteresis,
pulse width, runt pulse, dropout, windowed, logic
Maximum Pre-trigger Delay
The pre-trigger delay (0% to 100%) controls how much of the waveform appears before the trigger point (i.e. look back in time). It defaults to 50%, which puts the trigger marker in the middle of the screen. You can also control this parameter by dragging the trigger marker left or right.
Up to 100% of capture length
Maximum Post-trigger Delay
The post-trigger delay allows the signal to be shifted back so that the place on the waveform where the trigger event actually occurred is to the left of the yellow trigger diamond by a specified time period so that you can analyse what happened at a time after the trigger occurred.
Unwanted transfer of signal from one channel to another.
72dB (4000:1), DC to 20 MHz
76dB (6300:1), DC to 20 MHz
Ratio of signal harmonics to the fundamental frequency - an indication of the extent of unwanted distortion of the waveshape being measured (lower dB value is better - lower distortion). 60dB equates to 0.1% distortion.
< −60 dB
Spurious-free dynamic range is the strength of the fundamental signal when compared to spurious harmonic distortion and noise (higher dB is better)
Unwanted (usually random) disturbances or errors affecting signal measurement (lower is better).
220 μV RMS on 50 mV range
An indication of the amplitude consistancy with respect to frequency - does the amplitude of the measured signal change with frequency which would affect measurement accuracy at different frequencies? (lower is better)
DC to full bandwidth (+0.25 dB, −3 dB)
The effective number of bits of the ADC (resolution) when taking into account factors such as noise. (higher is better)
A spectrum analyser changes the display so that you can see the relative level of each frequency component of a signal. This can be a very useful feature when analysing vehicle noise sources.
DC to 20MHz
Magnitude : the frequency spectrum of the last waveform captured. Peak Hold : holds the peaks from all waveforms in the buffer on the display and increases them if they go higher until you reset them. Average : Averages the frequencies from all waveforms in the buffer which tends to reduce noise.
Magnitude, Peak Hold and Average
Number of FFT Points
Spectrum analysis uses a mathmatical technique called a Fast Fourier Transform (FFT). A time window is created containing sequential samples. The number of samples can be selected.
128 to 1 million in powers of 2
Spectrum analysis uses a mathmatical technique called a Fast Fourier Transform (FFT). A time window is created and the FFT algorithim configures the window as a loop - with the start connected to the end. The start and end will most probably not be at the same level which produces spurious artifacts in the result. Windowing is a technique where the signal levels are adjusted to zero at the start - end boundary to ensure that the levels match.