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Where to Buy TPI ProductsSelecting 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.

TPI 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.
Model # Image Bandwidth Accuracy Risetime CMRR (Typical) @ 50Hz CMRR (Typical) @ 20kHz CMRR (Typical) @ 200kHz Input Impedance Input Voltage Maximum Differential Output Voltage Offset (typical) Common Mode Noise (typical) Output Source Impedance Input Leads IEC1010
ADF25 DC -25 MHz (-3dB) ± 2% 14nS -80dB -60dB -50dB 4M/10pf each side to ground 8M/5pF between inputs ±140V DC Inc.Pk AC @ 20:1 or 100V RMS ± 1,400VDC Inc. Pk AC 200:1 or 1,000V RMS ± 7V minimum 2KΩ load <± 5mV -10° C to + 40° C ± 1,400V DC Inc. Pk AC or 1,000V RMS 0.7mV RMS 1Ω @ 1kHz. 8Ω @1 MHz 45 cm double insulated PVC terminated in 44 mm safety plugs CAT III
ADF25A DC -25 MHz (-3dB) ± 2% 14nS -86dB -66dB -56dB 4M/10pf each side to ground 8M/5pF between inputs ±170V DC Inc.Pk AC @ 10:1 or 50V RMS ± 1,400VDC Inc. Pk AC 100:1 or 500V RMS ± 7V minimum 2KΩ load <± 5mV -10° C to + 40° C ± 1,400V DC Inc. Pk AC or 1,000V RMS 0.7mV RMS 1Ω @ 1kHz. 8Ω @1 MHz 45 cm double insulated PVC terminated in 44 mm safety plugs CAT III
ADF25C DC -70 MHz (-3dB) ± 2% 14nS -80dB -60dB -50dB 10M/10pf each side to ground 20M/5pF between inputs ±700V DC Inc.Pk AC @ 100:1 or 400V RMS ± 7,000VDC Inc. Pk AC 1,000:1 or 5,000V RMS ± 7V minimum 2KΩ load <± 5mV -10° C to + 40° C ± 7,000V DC Inc. Pk AC or 2,500V RMS 0.9mV RMS 50Ω 60 cm double insulated Rubber terminated in sprung hooks CATII

TPI Oscilloscope Probes Documentation

Oscilloscope / Differential Probes


  • Use TPI Probes with Bench Top, Portable, Analog, and Oscilloscopes
  • Logic signal and waveform tests
  • Measure voice / data signals
  • Analyze power quality
  • Test motor control circuits

Frequently Asked Questions

Can TPI oscilloscope probes be used with Tektronix and Hewlett Packard scopes?
Yes, TPI oscilloscope probes can be used with most major brands of scopes.

Why is selecting a probe with the correct bandwidth important?
Choosing a probe with the correct bandwidth enables you to use your scope to its full potential.

Why do TPI oscilloscope probes have a compensation range and compensation adjustment?
Since the input of every oscilloscope is different our probes have a compensation adjustment so the capacitance of the probe can be adjusted to match the capacitance of the scope input. The compensation range is the range of adjustment available. Matching probe and scope capacitance is important to prevent waveform distortion.

What is the benefit of a probe with X1 and X10 switchable attenuation?
Passive X10 probes allow you to read a signal 10 times the amplitude of that viewed with a X1 probe. Example: an eight-division graticule on 5V/Div setting would display a 40 volt peak-to-peak signal using the X1 setting. You can view a 400 volt signal using the X10 setting.

What is readout?
Readout is an activator pin that protrudes out of the BNC connector of an X10 or X100 probe that completes a circuit. There are contacts around the BNC connector on the front of the oscilloscope and the attenuation is automatically set. If your scope does not have contacts around the BNC connector, it does not need this feature.

What probe should I buy?
Select a probe that is at least the same bandwidth as the oscilloscope you intend to use; however, for optimum performance, select a probe with two times the bandwidth of your test instrument.

What can you measure with a differential probe?
With 20 MHz bandwidth, a switchable attenuation of 20:1, and 200:1 (part no. ADF25), you can measure high-voltage circuits, motor speed controls, power supply design, and high-power electronic converters.

What comes in the probe set?
You will receive one differential probe, 2 probe tips, and 2 retractable sprung probes for accessing small wires for measurements.

Why is common rejection ratio (CMMR) important for differential probes?
CMMR is a measure of how well a differential probe will reject signals common to both test points, leaving the desired signal to be displayed by the scope.

What does the maximum differential voltage specification tell me?
This specification provides you with the maximum voltage between the inputs the differential probe can be subjected to. This is important because the maximum voltage should never be exceeded.

What is input impedance?
Impedance is a measure of how much a signal will be restricted. In general, it is best to have high resistance and low capacitance to ensure signal quality, accuracy of tests, and to ensure the probe doesn’t load down the circuit under test.  

Tech Tips
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.


  • 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.
  • 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
  • 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.
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