Oscilloscope / Differential Probe Selection

Selecting the correct oscilloscope probe ensures accuracy and can improve the performance of your test instrument. TPI offers a wide range of high quality oscilloscope probes designed to meet the most demanding applications.

The IP series monolithic probes have switchable attenuation and are available in 60 and 250MHz. These probes are ideal for technicians that need a basic oscilloscope probe.

The slimline design P and SP series probes are available in fixed or switchable attenuation. These series of probes are perfect for the technician needing additional features such as replaceable cable and interchangeable probe tip. The compensation adjustment for these probes is located in the BNC to eliminate noise pickup.

TPI also offers three models of high voltage differential probes all with high common mode rejection, wide bandwidth, and fast rise times. Differential probes enable the viewing of signals not referenced to earth ground and provide better performance than a matched pair of single ended oscilloscope probes when measuring these types of signals.

Several important factors must be taken into account when selecting the proper probe.

• The probe should have sufficient bandwidth and rise time for the test instrument and application. Choose a probe with at least an equal bandwidth as the scope it will be used with. For best performance a probe with twice the bandwidth as the scope should be selected.
• For oscilloscope probes, the input capacitance of your oscilloscope should be within the compensation range specification of the probe. In addition, if your oscilloscope has readout function, select a probe with this capability.
• For differential probes, make sure the maximum differential voltage is adequate for your application and the common mode rejection specification meets the requirements of the tests being performed. Refer to the oscilloscope and differential probe specification tables to select the correct probe for your application.

Oscilloscope / Differential Probe Terminology

>>Attenuation: Ratio of the output signal to the input signal. Attenuation should remain constant decreasing by 3dB only as the frequency increases to the maximum bandwidth.

>>Bandwidth: The maximum -3dB frequency that can be expected.

>>Cable Length: Length of the cable from the end of the probe to the end of the connector. It is important to use a probe with just enough cable length for your needs. Long cables increase the capacitance and propagation delay of the probe.

>>Compensation Range: The range a probe can be compensated to match the input capacitance of the test equipment it is being used with.

>>IEC 1010: Probes with the IEC 1010 category rating have been designed for safety.

>>Input Impedance: The total resistance and capacitance as measured at the tip of the probe. This specification is used to define the loading effect of a probe. At frequencies under 1MHz the input resistance of the probe will have the most influence. At higher frequencies the input capacitance will have the most influence.

>>Max Input Voltage: The maximum voltage the probe can be used at.

>>Max Differential Voltage: The maximum differential voltage that can be measured by a differential probe.

>>Readout: Probes with this capability are compatible with readout function oscilloscopes that automatically detect and display the attenuation factor of the probe.

>>Rise Time: The time required for the leading edge of a pulse to rise from 10% to 90% of its final value.

>>CMRR: Common Mode Rejection Ratio. A measure of a differential probes ability to reject any signals common to both test points in a differential measurement.