Data Acquisition

An analog trigger on a single channel of the board or from an external analog triggersource starts the acquisition.The threshold level and slope at which the trigger begins the acquisition is commonlyprogrammable. A high resolution DAC output generates the programmed voltagethreshold, which is then compared to the analog voltage level from the trigger input.When the two voltage levels are equal and the slope polarity of the trigger is correct, theacquisition begins.Where a trigger capability is specified as above or below level, only the value of theanalog input trigger and its level with regard to a programmable threshold, is considered.The trigger slope is ignored.An external digital trigger input, TTL compatible and programmable as active on therising or falling edge, triggers the acquisition process. When using the digital triggermode, some boards specify a minimum pulse width – be wary of this!The data acquisition process is started by a call from software.Some boards have dual-trigger capability, which allows triggering to occur on acombination of trigger inputs. The data acquisition will not occur unless both triggerinputs reach their programmed threshold levels.Logic analyzers and digital storage oscilloscopes, which allow multi-event, multi-levelor sequential trigger modes, are examples of equipment that require more complextriggering capabilities.