This Acquisition section of the control panel also indicates the number of waveforms acquired per second by the digitizer. The use of each of the acquisition modes is described below. In the discussion, a valid trigger indicates a trigger signal meeting the trigger conditions at a time when the digitizer is armed and ready to acquire data. In Single and Normal modes the display will only be updated after each active digitizer has received a trigger.
Stop will stop the acquisition and hold the latest complete acquisition on the display.
Single mode is used in order to capture one event at the first valid trigger. It freezes the acquisition in the digitizer’s memory, and on the display, until the user requests another acquisition. After an acquisition is taken in Single mode, the digitizer will ignore subsequent trigger events until the Single button is pressed again or another acquisition mode is selected. Pressing the single button
Normal mode is used to continuously acquire waveforms into memory for valid trigger events. The display is updated with the new acquisitions in accordance with the Display Refresh Rate setting under the Options menu on the top line of the AcqirisLive Control window. Acquisitions will happen for each valid trigger until either single or Stop is pressed.
If the trigger indicator at the lower left of the waveform display does not blink green, the digitizer is not receiving valid triggers. Check the trigger settings or select Auto mode in order to obtain a display of the waveform.
Auto mode will acquire and display waveforms according to the trigger settings if a valid trigger is present within a timeout interval. If a valid trigger is not available within this interval, the digitizer generates its own trigger in order to digitize and display whatever signal is at the input at that time.
If valid triggers are received at a high enough rate, Auto mode behavior differs little from normal mode behavior on the display. However if the trigger rate is too low or trigger settings are not appropriate for the characteristics of the signal, the input signal will not be stable on the display. This occurs because the internal
Auto mode is often used to aid in setup when the input signal must be quickly characterized in order to determine proper trigger settings for Normal or Single mode acquisitions.
4.2.8. Timebase and Memory
The timebase and memory settings should be chosen together in order to optimize the desired sample rate for the acquisition.
In oscilloscope mode | the | timebase | settings | range | from |
10 ns/div to 5 S/div. | In | Transient | Recorder | mode | time |
windows of 100 ns to 20 Ks are available when using a card with the 2 Mpoint memory option.
In order to change the timebase click on the white area in the timebase display window and select the desired timebase from the list. Alternatively, the Decrement /
Increment timebase selection buttons may be used in order to change the timebase in steps with each click of the mouse. The sample rate and sample interval resulting from the combination of memory and timebase are indicated under the Sampling section of the control panel.
The Memory setting shows the maximum number of points to be acquired. The actual number of points acquired could be less than the maximum number set if the acquisition time window selected fills less than the selected amount of memory at the full sample rate. Alternatively, in oscilloscope mode, if a slower timebase is selected, in order to ensure that the selected amount of memory will be filled before the acquisition is complete, the digitizer will reduce its sample rate as necessary. This action differs from the same case in Transient Recorder mode where preference is given to the selected sample interval.
In Transient Recorder mode, the digitizer will continue to allocate more memory with increasing capture times. This is done in order to maintain the selected sample interval for as long a time window as is possible given the available memory. When the card memory is fully utilized, the sample rate will decrease with increasing capture times.
4.2.9. Using digitizers of different models simultaneously
AcqirisLive features a single timebase (i.e. the set of acquisition parameters pertaining to the time axis of the waveform, such as the sampling rate and the number of samples). It is therefore not possible to specify different timebase settings for different digitizers. However, it is possible to run each digitizer at its maximum available sampling rate performance in the following way:
•Select the Scope mode.
User Manual: Family of | Page 46 of 66 |
