Engineers working with National Instruments' DAQmx counter boards have surfaced a quirk that matters far more than its technical footnote might suggest: the Initial Delay parameter in the "Gen Digital Pulse Train Finite Retriggerable" example only applies to the very first trigger event. Every subsequent trigger fires its pulse train immediately, with no delay at all. For anyone building automated test systems, laboratory instrumentation, or synchronized measurement rigs, that distinction is not cosmetic. It can mean the difference between a dataset that is trustworthy and one that silently drifts out of alignment with the event it was meant to measure.
The behavior, confirmed by National Instruments engineers on hardware ranging from the 6602 counter/timer board to E Series multifunction cards, turns out to be by design rather than a bug. The counters that generate finite pulse trains are built to treat the delay as a one-time setup cost: once the hardware is armed and the first pulse sequence has respected the requested delay, later retriggers are assumed to need no further pause. That assumption works fine for many single-shot or infrequent triggering scenarios, but it breaks down for applications that need a consistent, repeatable delay on every single trigger - a common requirement in repetitive stimulus-response testing, ultrasonic transducer control, or any protocol where timing jitter is unacceptable. Readers who manage distributed lab equipment across multiple machines may already rely on consolidated software licensing, the same way IT teams increasingly favor one subscription for every device to simplify security and access management across an entire fleet of instruments and controllers. one subscription for every device
A Workaround Built From Two Counters
The accepted solution, worked out in direct correspondence between NI applications engineers and end users, is to combine two counters rather than rely on one. The first counter is configured as a retriggerable single pulse, with its low time set to the desired initial delay and its high time set to a chosen duration. That counter's output then serves as a pause trigger for a second counter running a continuous pulse train at the frequency the application actually needs. In effect, the first counter acts as a gate: it stays low for the delay period, then goes high, which releases the second counter to generate pulses for exactly that high interval. The approach reproduces the desired delay-then-pulse pattern on every trigger, not just the first, and it works on boards with as few as two counters - a meaningful constraint for anyone using an E Series card rather than a 6602 or 6601 with its eight available counters.
Why Counter Count Still Matters
The conversation also exposed a practical limitation that trips up many system designers: generating any finite pulse train already consumes two counters, so adding a triggering counter on top of that pushes the total to three. That is trivial on a 6602, which offers eight counters, but impossible on a standard E Series board limited to two. Applications that also need to perform event or period measurement - common in timing-sensitive instrumentation - require a third counter regardless, which is why experienced users often standardize on 6602 or 6601 hardware from the outset rather than retrofitting a design built around a smaller board.
A Feature Request With Lasting Relevance
One of the more telling exchanges in this saga is the suggestion that NI simply add a parameter - "use Initial Delay for all triggers" - directly to the retriggerable pulse example, assuming the underlying hardware could support it. NI engineers acknowledged the request and said it was being considered for future versions of NI-DAQ. For developers working outside LabVIEW, the same timing control is available at the API level: the DAQmxSetStartTrigDelay and DAQmxSetStartTrigDelayUnits functions let C and C++ programmers specify a wait period after a start trigger before generation or acquisition begins, offering a lower-level path to the same precise timing behavior that graphical example VIs do not expose by default.