Oscilloscopes
Protocol Analyzers
Differential Amplifiers
Probes
Current Probes
Active Probes
Passive Probes
Differential Probes
High-Voltage Probes
Transmission Line Probes
OE Converters
Probe Accessories
Automotive/Vehicle Test
Mixed Signal Test Solutions
Modular Instruments
Scope Accessories
Hardware Options
Software Options
Discontinued Products
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LeCroy
has recently added a wide variety of world class
probes and amplifiers to it's product line. The
DA1800A series of differential amplifiers and probes,
the 500 MHz AP033 differential probe, PPE series of
six high voltage probes, AP015 (50 MHz, 50 Amp), current probes and a wide
selection of active and passive probes with
bandwidths to 6 GHz are available.
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Current
Probes
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Current Probes
measure the current passing through a wire; current probes do not use the
"traditional" probing style of placing a tip onto a test point.
Rather, a wire is placed inside of the "jaw" of the probe, which
then allows the probe to measure the current (in Amps).
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Active Probes |
There are two different types of active probes: "single-ended" and "differential."
Single
Ended:
A single-ended active probe is associated with measuring voltages at high
frequencies. Measurement with an active probe requires a test point and a
ground point. The ground (also called earth) acts as a zero reference for
the test point measurement.
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Differential
Probes
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Differential active probes are like two probes in one. Instead of measuring a test point in relation to a ground point (like single-ended active probes), differential probes measure the difference in voltage of a test point in relation to another test point.
Differential
Probes <1 GHz
Differential
Probes >10 GHz
Differential
Probes WaveLink Series
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Passive
Probes
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Passive probes
measure voltages at lower frequencies (<400 MHz). They have higher input
capacitance (input C) and do not need power to operate (unlike active
probes). At higher frequencies, higher input capacitance loads the test
circuit, attenuating the signal. This is why active probes are used in high
frequency applications. Passive probes also measure voltage in reference to
ground.
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High-Voltage Probes
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These are
active single ended probes that are designed to measure high voltages
(safely). They measure the voltage in reference to ground.
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Transmission Line Probes
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Transmission line probes are a
special type of passive probe designed for use at very high frequencies.
They replace the high impedance probe cable found in a traditional passive
probe with a precision transmission line, with a characteristic impedance
that matches the oscilloscope input (50W). This
greatly reduces the input capacitance to a fraction of a picofarad,
minimizing the loading of high frequency signals. A matching network at the
tip increases the DC input resistance. While they have lower DC input
resistance than a traditional passive probe (usually 500 W
to 5 kW), the input impedance of these probes
remains nearly constant over their entire frequency range. A traditional ¸10
passive probe will have a 10 MW input impedance
at DC, however this impedance drops rapidly with frequency, passing below
the input impedance of a transmission line probe at less than 100 MHz.
In some applications,
transmission line probes offer advantages over active probes. In addition to
being less expensive, their passive design is more robust to over voltage
and ESD exposure. They are useful in applications producing fast rising,
narrow pulses with amplitudes which exceed the dynamic range of active
probes. They also tend to have less parasitic effects on frequency response.
A high BW transmission line probe driving a sampling oscilloscope can be
used as a "golden standard" in situations when the response of an
active probe measurement is questioned.
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