Performing probe calibration (commonly referred to as "compensation") is a crucial step before using a Tektronix oscilloscope. If you skip this step, it may cause waveform distortion, and the measured voltage value may be too high or too low, which can mislead your circuit debugging.

Due to the wide range of Tektronix oscilloscope models, I will provide a detailed introduction to two main calibration methods for the most common passive probes (such as TPP series, P5122, etc.): automatic calibration (applicable to new digital probes) and manual adjustment (applicable to traditional passive probes).

preparation

Before starting, please make sure to complete the following steps:

Power on preheating: Turn on the oscilloscope and preheat for a few minutes to ensure that the internal circuit reaches a stable state.

Connect the probe: Connect the probe to the channel of the oscilloscope (such as CH1).

Connect calibration signal: Hook the probe tip and end onto the "Probe Comp" output terminal on the front panel of the oscilloscope, and clamp the probe's grounding clip onto the adjacent grounding terminal (crocodile clip).

Set attenuation coefficient: Confirm that the switch on the probe (if any) is consistent with the settings in the oscilloscope menu (usually 10X).

Method 1: Automatic calibration (applicable to new probes such as TPP1000)

If your probe is from Tektronix's TPP series (such as TPP1000, TPP0500, etc.), there is no adjustable capacitor knob inside the probe, and all calibration is completed through software inside the oscilloscope.

Operation steps:

Enter the menu: On the oscilloscope panel, double-click (or press) the channel button (e.g. CH1) where you connect the probe.

Select probe settings: In the pop-up menu, find and select "Probe Setup".

Start calibration: Select "Probe Cal" or "Compensate Probe".

Auto execution: Click on the "Calibrate Probe" button.

View result: The oscilloscope will automatically output the signal and analyze the waveform, and the screen will display "Pass" or "Fail".

Attention: If 'failed' is displayed, please check if the grounding is secure, or try unplugging and reinserting the probe to recalibrate.

Method 2: Manual adjustment (applicable to traditional probes such as P5122)

If your probe has an adjustable capacitor knob (usually a small hole), or if automatic calibration cannot correct the waveform, you need to manually adjust it.

Operation steps:

Display waveform: Press the "Autoset" button on the front panel of the oscilloscope, and a square wave should appear on the screen.

Observing waveform: Determine the compensation status of the probe based on the shape of the waveform.

Adjustment knob: Use a non sensitive screwdriver to gently insert the adjustment hole (compensating capacitor) on the probe and slowly rotate.

Undercompensation: The waveform has a smooth top and indistinct edges.

Overcompensation: The waveform peaks at the top, resembling a roof.

Goal: Adjust to the top of the waveform to be straight and sharp.

Comparison Table of Abnormal Waveforms and Adjustments

During manual adjustment, you may see the following three waveforms. Please refer to the table below for adjustments:

Special Notice

Channel binding: Probe calibration is specific to a particular channel. If you unplug the probe from CH1 and plug it into CH2, you must recalibrate it because there may be slight differences in input capacitance between different channels.

Environmental changes: If the temperature in your laboratory undergoes drastic changes, or if you replace the tip or end accessories of the probe (such as hooks, spring grounding, etc.), it is recommended to recheck the compensation status.

High voltage probe: If it is a high voltage probe (such as P5122), please make sure to only touch the insulation adjustment tool when adjusting the compensation capacitor to avoid the risk of electric shock.

Now, you can choose the corresponding method for operation based on your probe type. If the waveform cannot be flattened during the adjustment process, it may be due to noise introduced by the probe grounding being too long. It is recommended to use a spring grounding accessory to retry.

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