Oscilloscope Reference Logic state inputs
Logic state inputs
Channels 1, 2, and 3 represent the data inputs. Channel 4 should be connected to the clock signal. The
channel inputs combine to form a logic pattern.
Each channel can have a value of high (H), low (L), or "don't care" (X).
A value is considered high if the channel input voltage is greater than the specified threshold voltage.
A value is considered low if the channel input voltage is less than the specified threshold voltage.
Use the "don't care" selection for any channels that will not be used a s part of the pattern.
Logic state trigger criteria
Use the Trigger When Pattern selection to determine when the instrument should trigger.
Select True to trigger the instrument when the logic patterns go true.
Select False to trigger the instrument when the logic patterns go false.
Low
The low level measurement is the value used as 0% whenever high reference, mid reference, or low
reference values are needed, such as in fa ll time or rise
time measurements.
This value can be calculated using either the min/max or histogram method. The min/max method uses the
minimum value found. The histogram method uses the most common value found below the midpoint.
This value is measured over the entire waveform or gated region.
Low impedance probes
Most low impedance (Z
o
) passive probes measure frequencies or timing measurements more accurately
than general-purpose probes, but they take less accurate amplitude measurements. They offer a higher
bandwidth to cost ratio.
The low input impedance passive probes must be terminated in a 50 Ω instrument input. Input capacitance
is much lower than high impedance passive probes, typically 1 pF, but input resistance is also lower
(500 Ω to 5000 Ω typically). Although that DC loading degrades amplitude accuracy, the lower input
capacitance reduces high frequency loading to the circuit under test. That makes low input impedance
passive probes ideal for timing and phase measurements when amplitude accuracy is not a major concern.
Low input passive impedance probes are useful for measurements up to 40 V.
DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series 851
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