If you have a requirement for more than 4 oscilloscope input channels it is possible to synchronize two or more WavePro or WaveMaster series scopes to obtain a system with 8 or more channels. The process is relatively simple but requires attention to detail to insure correct timing. A block diagram of the basic configuration is illustrated below in Figure 1. Digital oscilloscopes that include the External Reference feature can be synchronized by 1) locking their timebases together and 2) by using a common trigger. The WaveMaster 8600, WaveMaster 8Zi and WavePro 7Zi series include the external reference input, as well as SDA and DDA scopes that use the WaveMaster or WavePro platform.

Figure 1:

Configuration block diagram for synchronizing two WaveMaster oscilloscopes

Timebase synchronization is achieved by applying the same external reference signal to the rear panel external reference inputs. The WaveMaster 8600 series requires a 100MHz signal; the 8Zi and 7Zi series require a 10MHz signal. The signal source used should have frequency stability equal to or better than the scope's ≤1 ppm internal timebase. Short term jitter of the timebase should be better than 0.5 ps rms in order to maintain the scope's ≤1 ps jitter noise floor.

Note that the external reference input requires a signal level of 0 to either 3dBm or 10db (10dBm for the Zi series oscilloscopes). Since the reference input signal is transmitted through a splitter, the generator must be adjusted to compensate for insertion loss which in this example was 6 dB. The signal paths from the splitter to the scopes should be equal in length and connected with the same type of cable.

Figure 2:

Adjusting deskew to align waveforms using average delay

Figure 3:

Selecting external clock reference from the timebase setup

In a similar manner the trigger signal is split and connected to each scope with identical length cables of the same type.

Once the scopes are connected, select "External Reference Clock" from the Clock Source tab in the Timebase Horizontal Setup menu (Figure 2) and configure the oscilloscope to use the external trigger in the Trigger Setup dialog on both scopes. Trigger levels should also be inspected and adjusted if needed so that both scopes have the same trigger level setting.

Next, deskew the inputs by applying the same signal to each input and use the deskew function in the Vertical Channel Setup menu to monitor the average value of the automatic parameter measurement "delay". "Delay" measures the time difference between the trigger point and the (50% amplitude) leading edge of the waveform, verifying time alignment. For best results the input waveform should have a fast, well defined edge. Each input channel should be adjusted for the same vertical sensitivity (Volts/Div) range that will be used in the actual measurement.

If an external trigger signal is not available then one of the input waveforms can be used as a trigger signal. In this case the signal must be split and sent to both scopes. The common trigger signal can be displayed (at the cost of losing an input channel) and used for visual as well as parametric alignment.