Tektronix TDS210 user guide: Application Examples

Application Examples

This section presents a series of application examples. These simplified examples highlight the features of the oscilloscope and give you ideas for using it to solve your own test problems.

■ Taking simple measurements Using Autoset Using the Measure menu to take automatic measurements Measuring two signals and calculating gain

■ Taking cursor measurements Measuring pulse width Measuring rise time Measuring ring frequency and ring amplitude

■ Analyzing signal detail Looking at a noisy signal Using the average function to separate a signal from noise

■ Triggering on a video signal Triggering on video fields and video lines Using the window function to see waveform details Triggering on odd or even video fields

■ Analyzing a differential communication signal Using math functions

■ Viewing impedance changes in a network Using XY mode Using persistence

Application Examples

Taking Simple Measurements

You need to see a signal in a circuit, but you do not know the amplitude or frequency of the signal. You want to quickly display the signal and measure the frequency, period, and peak-to-peak amplitude.

Using Autoset

To quickly display a signal, do these steps:

1. Set the Probe menu attenuation to 10X. Set the switch to 10X on the P2100 probe.

2. Connect the channel 1 probe to the signal.

3. Push the AUTOSET button.

The oscilloscope sets the vertical, horizontal, and trigger controls automatically. If you want to optimize the display of the waveform, you can manually adjust these controls.

When you use more than one channel, the autoset function sets the vertical controls for each channel and uses the lowest-numbered active channel to set the horizontal and trigger controls.

Application Examples

Taking Automatic Measurements

The oscilloscope can take automatic measurements of most displayed signals. To measure signal frequency, period, and peak-to-peak amplitude, do these steps:

1. Push the MEASURE button to see the Measure menu.
2. Push the top menu box button to select Source.
3. Select CH1 for the first three measurements.
4. Push the top menu box button to select Type.
5. Push the first CH1 menu box button to select Freq.
6. Push the second CH1 menu box button to select Period.
7. Push the third CH1 menu box button to select Pk-Pk.

The frequency, period, and peak-to-peak measurements are shown in the menu and are updated periodically.

Application Examples

Measuring Two Signals

You are testing a piece of equipment and need to measure the gain of the audio amplifier. You have an audio generator that can inject a test signal at the amplifier input. Connect two oscilloscope channels to the amplifier input and output as shown. Measure both signal levels and use the measurements to calculate the gain.

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Application Examples

To activate and display the signals connected to channel 1 and to channel 2, do these steps:

1. If the channels are not displayed, push the CH 1 MENU and then CH 2 MENU buttons.

2. Push the AUTOSET button.

To select measurements for the two channels, do these steps:

1. Select the source channels. a. Push the MEASURE button to see the Measure menu. b. Push the top menu box button to select Source. c. Push the second menu box button to select CH1. d. Push the third menu box button to select CH2.

2. Select the type of measurement displayed for each channel. a. Push the top menu box button to select Type. b. Push the CH1 menu box button to select Pk-Pk. c. Push the CH2 menu box button to select Pk-Pk.

3. Read the peak-to-peak amplitudes for channel 1 and channel 2 in the menu display.

4. Calculate the amplifier gain using the following equations:

$$ \text{Gain} = \frac{\text{output amplitude}}{\text{input amplitude}} $$

$$ \text{Gain (dB)} = 20 \times \log(\text{Gain}) $$

Application Examples

Taking Cursor Measurements

You can use the cursors to quickly take time and voltage measurements on a waveform.

Measuring Pulse Width You are analyzing a pulse waveform, and you want to know the width of the pulse. To measure the width of a pulse using the time cursors, do these steps:

1. Push the CURSOR button to see the Cursor menu.
2. Push the top menu box button to select Time.
3. Push the Source menu box button to select CH1.
4. Use the CURSOR 1 knob to place a cursor on the rising edge of the pulse.
5. Use the CURSOR 2 knob to place the remaining cursor on the falling edge of the pulse.

You can see the following measurements in the Cursor menu:

• The time at Cursor 1, relative to the trigger.
• The time at Cursor 2, relative to the trigger.
• The delta time, which is the pulse width measurement.

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Application Examples

Type Time Source CH1 Delta 670.0µs 1.493kHz Cursor 1 1.330ms Cursor 2 2.000ms

NOTE. The TDS2MM extension module provides pulse width as an automatic measurement.

Measuring Rise Time

After measuring the pulse width, you decide that you need to check the rise time of the pulse. Typically, you measure rise time between the 10% and 90% portion of the waveform. To measure the rise time, do these steps:

1. Adjust the SEC/DIV knob to display the rising edge of the waveform.
2. Adjust the VOLTS/DIV knob to set the waveform amplitude to about five divisions.
3. Push the CH 1 MENU button to see the CH1 menu if it is not displayed.
4. Push the Volts/Div button to select Fine.

Application Examples

5. Adjust the VOLTS/DIV knob to set the waveform amplitude to exactly five divisions.
6. Use the VERTICAL POSITION knob to center the waveform; position the baseline of the waveform 2.5 divisions below the center graticule.
7. Push the CURSOR button to see the Cursor menu.
8. Push the top menu box button to set the type to Time.
9. Use the CURSOR 1 knob to place the cursor at the point where the waveform crosses the second graticule line below center screen. This is the 10% point on the waveform.
10. Use the CURSOR 2 knob to place the second cursor at the point where the waveform crosses the second graticule line above center screen. This is the 90% point on the waveform.
11. The delta readout in the cursor menu is the rise time of the waveform.

NOTE. The TDS2MM extension module provides rise time as an automatic measurement.

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Application Examples

Measuring Ring Frequency

To measure the ring frequency at the rising edge of a signal, do these steps:

1. Push the CURSOR button to see the Cursor menu.
2. Push the top menu box button to select Time.
3. Use the CURSOR 1 knob to place a cursor on the first peak of the ring.
4. Use the CURSOR 2 knob to place a cursor on the second peak of the ring.

You can see the delta time and frequency (the measured ring frequency) in the Cursor menu.

Application Examples

Measuring Ring Amplitude

You measured the ring frequency in the previous example. Now you want to measure the amplitude of the ringing. To measure the amplitude, do these steps:

1. Push the CURSOR button to see the Cursor menu.
2. Push the top menu box button to select Voltage.
3. Use the CURSOR 1 knob to place a cursor on the highest peak of the ring.
4. Use the CURSOR 2 knob to place a cursor on the lowest point of the ring.

You can see the following measurements in the cursor menu:

■ The delta voltage (peak-to-peak voltage of the ringing)

■ The voltage at Cursor 1

■ The voltage at Cursor 2

Type Voltage

Source CH1

Delta 121mV

Cursor 1 316mV

Cursor 2 437mV

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Application Examples

Analyzing Signal Detail

You have a noisy signal displayed on the oscilloscope and you need to know more about it. You suspect that the signal contains much more detail than you can now see in the display.

Looking at a Noisy Signal

The signal appears noisy and you suspect that noise is causing problems in your circuit. To better analyze the noise, do these steps:

1. Push the ACQUIRE button to see the Acquire menu.
2. Push the Peak detect button.
3. If necessary, push the DISPLAY button to see the Display menu. Use the Contrast Increase and Contrast Decrease menu box buttons to adjust the contrast to see the noise more easily.

Peak detect emphasizes noise spikes and glitches in your signal, especially when the time base is set to a slow setting.

Application Examples

S eparating the Signal from Noise

Now you want to analyze the signal shape and ignore the noise. To reduce random noise in the oscilloscope display, do these steps:

1. Push the ACQUIRE button to see the Acquire menu.

2. Push the Average menu box button.

3. Push the Averages menu box button to see the effects of varying the number of running averages on the waveform display.

Averaging reduces random noise and makes it easier to see detail in a signal. In the example below, a ring shows on the rising and falling edges of the signal when the noise is removed.

Application Examples

Capturing a Single-Shot Signal

The reliability of a reed relay in a piece of equipment has been poor and you need to investigate the problem. You suspect that the relay contacts arc when the relay opens. The fastest you can open and close the relay is about once per minute so you need to capture the voltage across the relay as a single-shot acquisition.

To set up for a single-shot acquisition, do these steps:

1. Adjust the vertical VOLTS/DIV and horizontal SEC/DIV to appropriate ranges for the signal you expect to see.
2. Push the ACQUIRE button to see the Acquire menu.
3. Push the Peak detect button.
4. Push the TRIGGER MENU button to see the Trigger menu.
5. Push the Mode button to select Single (single sequence).
6. Push the Slope button to select Rising.
7. Use the LEVEL knob to adjust the trigger level to a voltage midway between the open and closed voltages of the relay.
8. If the readout at the top of the screen does not display Armed or Ready, then push the RUN/STOP button to start the acquisition.

When the relay opens, the oscilloscope is triggered and captures the event.

Application Examples

Optimizing the Acquisition

The initial acquisition shows the relay contact beginning to open at the trigger point. This is followed by a large spike that indicates contact bounce and inductance in the circuit. The inductance can cause contact arcing and premature relay failure.

You can adjust the vertical, horizontal, and trigger controls to optimize the settings before the next single-shot event is captured.

When the next acquisition is captured with the new settings, you can see more detail about the relay contact opening. You can now see that the contact bounces several times as it opens.

Application Examples

Measuring Propagation Delay

You suspect that the memory timing in a microprocessor circuit is marginal. Set up the oscilloscope to measure the propagation delay between the chip-select signal and the data output of the memory device.

Application Examples

To set up to measure propagation delay, do these steps:

1. If the channels are not displayed, push the CH 1 MENU and then CH 2 MENU buttons.
2. Push AUTOSET to trigger a stable display.
3. Adjust the horizontal and vertical controls to optimize the display.
4. Push the CURSOR button to see the Cursor menu.
5. Push the top menu box button to select Time.
6. Push the Source menu box button to select CH1.
7. Use the CURSOR 1 knob to place the cursor on the active edge of the chip-select signal.
8. Use the CURSOR 2 knob to place the second cursor on the data output transition.
9. Read the propagation delay in the Delta readout in the cursor menu.

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Application Examples

Triggering on a Video Signal

You are testing the video circuit in a piece of medical equipment and need to display the video output signal. The video output is an NTSC standard signal. Use the video trigger to obtain a stable display.

75 Ω terminator

CH 1

Application Examples

Triggering on Video Fields To trigger on the video fields, do these steps:

1. Push the TRIGGER MENU button to see the Trigger menu.
2. Push the top menu box button to select Video.
3. Push the Sync menu box button to select Field.
4. Adjust the horizontal SEC/DIV knob to see a complete field across the screen.
5. Push the HORIZONTAL MENU button to see the Main menu.
6. Push the Trig knob menu box button to select Holdoff.
7. Adjust the HOLDOFF knob to an appropriate period. You can use about 21 ms for NTSC (and PAL) video.

Triggering on Video Lines You can also look at the video lines in the field. To trigger on the lines, do these steps:

1. Push the TRIGGER MENU button to see the Trigger menu.
2. Push the top menu box button to select Video.
3. Push the Sync menu box button to select Line.
4. Adjust the horizontal SEC/DIV knob to see a complete video line across the screen.

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Application Examples

Using the Window Function to See Waveform Details You can use the window function to examine a specific portion of a waveform without changing the main display.

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Application Examples

If you want to view the color burst in the previous waveform in more detail without changing the main display, do these steps:

1. Push the HORIZONTAL MENU button to see the Horizontal menu and select Main.
2. Adjust the horizontal SEC/DIV knob to select 50 ms.
3. Push the Trig knob menu box button to select Holdoff.
4. Adjust the HOLDOFF knob to 61 ms.
5. Adjust the horizontal SEC/DIV knob until you see a whole line.
6. Push the Window Zone menu box button.
7. Adjust the SEC/DIV knob to set the width of the window (area to be expanded).
8. Adjust the HORIZONTAL POSITION knob to position the window around the portion of the waveform you want to expand.

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Application Examples

9. Push the Window button to see the expanded portion of the waveform.
10. Adjust the SEC/DIV knob to optimize viewing the expanded waveform.

To switch between the Main and Window views, push the Main or Window menu box button in the HORIZONTAL MENU.

Triggering on Odd or Even Video Fields Your oscilloscope will trigger on both odd and even video fields, and make the data difficult to view because the line details are a half line apart. To remedy this, you can set the holdoff period to lock on just the odd or even field, which produces a stable display.

For example, the field rate for NTSC video is 60 Hz. For stable triggering, you should set the holdoff period to at least the field rate (16.7 ms), but not to more than twice the field rate (33 ms).

Application Examples

To trigger on only an odd or even video field, do these steps:

1. If channel 1 is not displayed, push the CH 1 MENU button.
2. Use the VERTICAL POSITION knob to place the waveform on the middle graticule line (position 0).
3. Adjust the VERTICAL VOLTS/DIV knob to 500 mV.
4. Push the Coupling menu box button to select DC.
5. Push the Probe menu box button to select 1X.
6. Push the TRIGGER MENU button to see the Trigger menu.
7. Push the top menu box button to select VIDEO.
8. Push the Polarity menu box button to select Normal.
9. Push the Source menu box button to select CH1.
10. Push the Sync menu box button to select Field.
11. Push the ACQUIRE button to see the Acquire menu.
12. Set SEC/DIV to 10 µs.
13. Adjust the HORIZONTAL POSITION knob to about 1.5 ms.
14. Push the HORIZONTAL MENU button to see the Main menu.

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Application Examples

15. Push the Trig knob menu box button to select Holdoff.
16. Adjust the HOLDOFF knob to 21 ms for NTSC and PAL video.

NOTE. To make a large adjustment to the holdoff period, adjust the SEC/DIV knob to 50 ms, adjust the HOLDOFF knob to 21 ms, and readjust the SEC/DIV back to the previous value.

Now the oscilloscope only triggers on an odd or an even field (but not both), and the line information is stable.

With 500 ns of holdoff time, you cannot see any line information because the alternating fields overlap

With 21 ms of holdoff time you can easily see one clear line

Application Examples

Analyzing a Differential Communication Signal

You are having intermittent problems with a serial data communication link, and you suspect poor signal quality. Set up the oscilloscope to show you a snapshot of the serial data stream so you can verify the signal levels and transition times.

Because this is a differential signal, you use the math function of the oscilloscope to view a better representation of the waveform.

CH 1 CH 2

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To activate the differential signals connected to channel 1 and channel 2, do these steps:

1. Set the Probe menu attenuation to 10X. Set the switch to 10X on the P2100 probes.
2. If the channels are not displayed, push the CH 1 MENU and then CH 2 MENU buttons.
3. Push the AUTOSET button.
4. Push the MATH button to see the Math menu.

TDS 210 and TDS 220 (Firmware V 2.00 and Above), and TDS 224 (All Versions) Oscilloscopes

Do these steps:

1. Push the Operation menu box button to select –.
2. Push the CH1–CH2 menu box button to display a new waveform that is the difference between the displayed waveforms.

For a more stable display, use the Run/Stop button to control the acquisition of the waveform. Each time you push the Run/Stop button, the instrument acquires a snapshot of the digital data stream. You can use the cursors or automatic measurements to analyze the waveform, or you can store the waveform to analyze later.

NOTE. Vertical sensitivity should match on waveforms used for math operations. If they do not match, and you use cursors to measure the waveform result, an U displays that represents unknown in the level and delta readouts.

Application Examples

TDS 210 and TDS 220 Oscilloscopes (Firmware Below V 2.00) without a TDS2MM Press the CH1–CH2 menu box button to display a new waveform that is the difference between the displayed waveforms.

TDS 210 and TDS 220 Oscilloscopes (Firmware Below V 2.00) with a TDS2MM Do these steps:

1. Push the CH2 MENU button and then push the CH2 Inverted menu box button to invert the signal on channel 2.
2. Push the MATH MENU button and then push the CH1+CH2 menu box button to display a new waveform that is the difference between the displayed waveforms.

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Application Examples

Viewing Impedance Changes in a Network

You have designed a circuit that needs to operate over a wide temperature range. You need to evaluate the change in impedance of the circuit as the ambient temperature is changed.

Connect the oscilloscope to monitor the input and output of the circuit and capture the changes that occur as you vary the temperature.

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Application Examples

To view the input and output of the circuit in an x-y display, do these steps:

1. Set the Probe menu attenuation to 10X. Set the switch to 10X on the P2100 probes.
2. Connect the channel 1 probe to the input of the network, and connect the channel 2 probe to the output.
3. If the channels are not displayed, push the CH 1 MENU and CH 2 MENU buttons.
4. Push the AUTOSET button.
5. Adjust the VOLTS/DIV knobs to display approximately the same amplitude signals on each channel.
6. Push the DISPLAY button to see the Display menu.
7. Push the Format menu box button to select XY.

The oscilloscope displays a Lissajous pattern representing the input and output characteristics of the circuit.

8. Adjust the VOLTS/DIV and VERTICAL POSITION knobs to display a desirable waveform.
9. Push the Persist menu box button to select Infinite.
10. Push the Contrast Increase or Decrease menu box buttons to adjust the contrast of the display for optimal viewing.

As you adjust the ambient temperature, the display persistence captures the changes in the characteristics of the circuit.