Setting Up A DSO to Display A Waveform

Setting the Digital Storage Oscilloscope (DSO) to display a waveform you want to see can be pretty tricky when connecting the Digital Storage Oscilloscope (DSO) to an unknown signal. Here are a few guidelines to get you up and running:

To display a waveform you must set:

1) Voltage scale

2) Time base

3) Trigger level, or trigger mode to "AUTO"

4) AC, DC, or GND coupling. DC coupling is used for most applications. DC coupling allows both AC and DC signals to be displayed. AC coupling filters out the DC component of the signal and only allows AC to be displayed. AC coupling is mostly used when looking at two wire, variable reluctance (magnetic) sensors, when looking for a noise in a signal, when checking alternator ripple voltage (diode check), or other rare instances. GND is used to position the ground, or zero level, of the DSO or to show where the zero voltage reference point is.

There are a few setups that can assist you in displaying a waveform:

1. Go into "OPERATION" on the left main menu and choose "AUTORANGE." After you get a recognizable waveform on the display, press any button on the control panel once to get the DSO out of "AUTORANGE" and into "MANUAL" mode to do your fine tuning.

2. If there still isn't a discernible waveform on the display, you can make an educated guess and set the voltage scale and trigger level. Leave the time base setting as the only unknown for the moment. Here's how: Use the DMM function of the DSO and measure the signal voltage. Adjust the voltage level to be about the same as the voltage reading. This should be a good starting point.

3. Now, set the trigger level to roughly half of the voltage signal. After setting the voltage scaling and the trigger level, the only unknown is the time base. Press the "POSITION/SCALE" button at the bottom of the control panel until "SCALE" appears at the right, lower corner of the display. Press the right and left arrow keys from one extreme to the other. The waveform should become visible somewhere in this exercise. Most automotive signals fall between 1 ms and 1 second per division time base.

4. The chart below may be used to help you select a time per division scale. Determine the frequency of the signal being checked by using the DMM function of the DSO. Then determine how many cycles you wish to see on the display at the same time.

Chart For Determining Time Base Setting, Based On Signal Frequency:

Cross the frequency of the signal and the number of cycles on the chart, and you will have a good starting point for a time base.