Teledyne LeCroy AP034 User Manual
Page 15
Operator’s Manual
922261-00 Rev A
9
High common mode rejection requires precise matching of the relative gain or attenuation in the +
and – input signal paths. Mismatches in additional parasitic capacitance, inductance, delay, and a
source impedance difference between the + and – signal paths will lower the common mode
rejection ratio. Therefore, it is desirable to use the same length and type of wire and connectors for
both input connections. When possible, try to connect the inputs to points in the circuit with
approximately the same source impedance.
If AC coupling is desired, install the AC coupling accessory on the probe tip before connecting it to
the test circuit. The low-frequency cutoff (–3 dB point) of the AC coupler is approximately 16 Hz.
If the voltage in the test circuit exceeds the probe’s capability, add the external ÷10 or ÷20
attenuator* to the probe tip. If both the external attenuator and AC coupler are used, install the
attenuator on the probe tip first, then install the AC coupler on the attenuator input.
CAUTION: The external attenuators are precisely adjusted during manufacturing to match the
characteristics of the input of the probe with which they were shipped. The input characteristics of
the external attenuator itself do not exactly match those of the probe. Therefore, using the ÷10
and ÷20 attenuators at the same time is not recommended. The scale factor encoding system will
not operate correctly with both attenuators installed simultaneously.
The input characteristics of the AP034 1 GHz Active Differential Probe are significantly different
than those of the AP033 500 MHz Active Differential Probe. The external attenuators are not
interchangeable. The external attenuators currently supplied with the probes are labeled with the
appropriate model number. The attenuators supplied with model AP033 probes prior to the
introduction of the AP034 did not include the model number on the label. When using an external
attenuator with the AP034 Active Differential Probe, make sure it is labeled “AP034.”
Interchanging non-compatible attenuators will not damage the probes; however, the transient
response of the measured signals will be significantly in error.
In addition to being compatible with the included lead set, the probe input connectors will mate
with standard 0.025 in. (0.635 mm) square pins in any rotational orientation. To avoid damaging
the input connectors, do not attempt to insert connectors or wire larger than 0.036 in. (0.91 mm) in
diameter. Avoid rotating square pins after they are inserted into the input connectors.
The included accessories simplify the task of connecting the probe to the test circuit:
Use the small (0.5 mm) mini clips with the flexible lead set when connecting to fine-pitch
surface mount IC leads.
Use the larger (0.8 mm) mini clips to connect to through-hole leaded components.
Use the offset round pins for hand-held probing applications. Reposition the pins by
rotating them to obtain the required spacing.