What are the methods for calibrating and repairing Tektronix oscilloscopes?

To prevent unauthorized and accidental adjustment operations, specific steps are required to enter adjustment mode. Different models and series of oscilloscopes may have different methods. Common ways to enter adjustment mode are:

1. Calibration switch

For example, for the Tektronix TDS200 series, the way to enter the adjustment mode is: when the oscilloscope is turned on, use a tool to press the button of the calibration hole on the rear panel, and at the same time press the "Utility" button on the front panel, and then enter the maintenance menu for adjustment.

Another example is the Tektronix TDS3000 series. The method to enter the adjustment mode is: while pressing the power start button to start the oscilloscope, use the tool to hold the calibration hole button on the rear panel of the oscilloscope until the oscilloscope starts, and then release the calibration button on the rear panel. At this time, you can enter the adjustment mode through the CAL submenu under the utility menu.

Tektronix digital oscilloscope calibration and adjustment method

2.Specific keys

For example, the Tektronix TDS2000C series can enter the measurement menu by pressing the "Measure" button on the front panel, pressing the top option button to enter the "Measurement 1" submenu, pressing and holding the "Single" button on the front panel, and then pressing Press the "Auto Set" button on the front panel, wait at least 2 seconds, and then release the "Single" button to enter the adjustment mode.

Another example is the Tektronix DPO2000 series. The method to enter the adjustment mode is to press the "Utility" key on the front panel after power-on and preheating, then select the "Calibration" submenu, and select the "Factory Pass" menu through the software. At this point, the Factory Calibration Passed dialog box will appear. Press and hold the top button on the right side of the screen (located below the "waveformonly" key) for about 5 seconds to enter factory adjustment mode.

two. Adjustment project introduction

1.DC voltage

The adjustment of this project usually uses a DC standard voltage source and inputs DC voltage signals to all measurement channels at the same time. The typical wiring pattern is shown in Figure 1.

Taking the TDS2000C oscilloscope as an example, there are 30 items of DC voltage adjustment, as shown in Table 1.

It should be noted that in order to ensure the adjustment effect, the calibration cables of each channel should be of equal length as much as possible, and the cable should not be too long (approximately 25cm is appropriate).

Some steps require setting the input voltage to 0.0000V, and some voltage sources may introduce noise or small AC signals when outputting 0V signals. In this case, after passing the adjustment procedure, the instrument may still fail the performance verification test. When the voltage source outputs a 0V signal, noise or small AC signals may be introduced. When the oscilloscope prompts that 0.000V voltage needs to be input, you can remove all signal lines from the oscilloscope (that is, do not connect any signal lines to the oscilloscope).

2.External trigger voltage

The adjustment of the project usually uses a DC standard voltage source and inputs the DC voltage signal into the external trigger of the oscilloscope. A typical wiring method is shown in Figure 2.

Taking the TDS2000C oscilloscope as an example, there are four external trigger voltage adjustments, as shown in Table 2.

3.AC voltage

The adjustment of this project usually uses a sine signal generator to input the sine signal of specified voltage and frequency into each measurement channel of the oscilloscope. The typical wiring pattern is shown in Figure 3.

It should be noted that when adjusting this project, the output impedance of the sinusoidal signal generator is usually set to 50ω; some oscilloscopes need to connect a 50ω matching resistor at the input end of the oscilloscope when adjusting this project, such as the TDS200 and TDS2000C series; some Oscilloscopes, such as the TDS3000 Series, do not require matching resistors. However, some oscilloscopes need to set the output impedance of the sine signal generator to 1mω. For details, refer to the maintenance manual of each oscilloscope.

Taking TDS2000C as an example, the typical adjustment steps are shown in Table 3, where "BWL" indicates the bandwidth of the oscilloscope.

4. Fast Edge

Tuning for this project typically uses a fast edge pulse signal generator to feed the signal into a designated channel of the oscilloscope.

Take TDS2000C as an example. If the oscilloscope has 2 channels, a fast-edge pulse signal with a frequency of 1kHz and a voltage of 0 ~ 800 mV needs to be input to channel 1. If the oscilloscope has 4 channels, you need to input fast edge pulse signals to channel 1 and channel 3 respectively. During the adjustment process, the output impedance of the fast edge signal generator should be set to 50ω, and the 50ω matching resistor should be connected to the input of the oscilloscope.

Another example is the TDS3000 series. Any fast-edge pulse signal with a frequency between 100 Hz and 1 MHz and a voltage between -2.2 V and 0 V needs to be input to each channel at the same time. The rise time of the signal is less than or equal to 1ns. During the adjustment process, the output impedance of the fast edge signal generator should be set to 50ω, and the input of the oscilloscope does not need to be connected to a 50ω matching resistor.