Scope Multimeter
Operation and Controls
87
Peak Detect On
When peak detect is “on”, all sample points are evaluated. The points stored to the
data buffer memory are intelligently selected to capture fast events that might be
missed at slower effective sample rates. Peak Detect captures fast events, spikes
and glitches for signals going in both positive and negative directions.
NOTES
— Turn peak detect "on" when capturing fast events (e.g. ignition firing
voltage, glitches, and intermittent events).
— Turning peak detect “on” may capture unwanted noise, therefore, using
peak detect may not be suitable for some tests (e.g. oxygen (O2) sensor), as
the waveform may be more difficult to evaluate due to the additional noise that
may be displayed.
— Peak Detect decreases the possibility of waveform aliasing.
To turn peak detect on and off, select the
Peak Detect
icon.
Filter
Using the filter feature can minimize or smooth out signal spikes and fast variations,
depending on which function is its used with.
Filter - Lab Scope
Using the filter with the lab scope, suppresses fast spikes and unwanted noise.
Using the filter is useful when working with scales of 5 volts and below, as the lower
the voltage scale, the more likely noise can occur.
Example:
Using the filter is helpful when testing components such as, an O2
sensor (1or 2 volt scale), or when performing a throttle position (TP) sensor
sweep test (5 volt scale).
In addition, the filter is also helpful for low amp probe tests, as a low voltage scale
is used to measure the output of the probe (due to the conversion factors of the
probe).
Example:
For a probe with a conversion factor of 100 mV/A connected to a 2
amp load, the scope uses a 200 mV scale to measure the output of the probe.
The scope converts the measured output to 2 amps for display on the screen.
Filter - GMM
Using the filter with the GMM, the filter minimizes noise by ignoring or smoothing
out fast signal spikes.
Note:
Using both Peak Detect and Filter provide a good
balance between noise suppression and capturing spikes (glitches).
•
For a direct measurement test, such as volts, amps, or pressure, the filter
minimizes the display of very fast spikes by averaging the sampled data when
filter is active.
•
For a calculated measurement test, such as frequency, pulse width, dwell, or
duty cycle, extremely fast spikes (20 µS and faster) from sources like the
ignition system are ignored when filter is active.
Note:
Peak is always on when
displaying calculated measurements such as frequency
To turn the filter on and off, select the
Filter
icon.
Invert
The Invert feature is used to switch signal polarity, so the trace appears upside
down (inverted) on the screen. This is typically used when measuring amperage
using the low amp probe, or high-voltage signals like, secondary ignition.
Example:
A signal that normally rises from 0 to +5 volts, if inverted would
show falling from 0 to –5 volts.
To turn inversion on/off, select the
Invert
icon.
Peak Detect Icons
On (Sampling maximized)
Off (Sampling not maximized)
Filter Icons
On (Interference is suppressed)
Off (Interference is not suppressed)
Invert Icons
On (Polarity is inverted)
Off (Polarity is not inverted)
