Underneath every K-factor and meter factor is a simpler, more physical thing: a stream of electrical pulses, one for each little parcel of volume the meter passes. A pulse output meter produces exactly that. This guide explains what those raw pulses are, how a dual A and B pulse pair lets a flow computer police the signal for faults, and what pulse fidelity levels mean for measurement you can defend.
Pulse Output Meter in one line: A pulse output meter produces a train of electrical pulses in which each pulse represents a fixed increment of volume passing through the meter, so the pulse rate is proportional to flow. A flow computer counts those pulses and applies the meter's K-factor to convert them to volume; many custody meters output dual A and B channels so the flow computer can check pulse security and fidelity.
A turbine, positive-displacement, or other pulse-producing meter generates one electrical pulse for each fixed increment of volume that passes - each blade passing a pickup, or each rotation of a measuring element. The faster the fluid flows, the faster the pulses come, so the frequency of the pulse train is directly proportional to flow rate, and the total count over a period is proportional to the total volume. The pulse train is the meter's raw, native output.
By itself a pulse is just an electrical event; it becomes volume only when scaled by the meter's K-factor, the number of pulses per unit volume. A flow computer accumulates the pulse count and divides by the K-factor to get an indicated volume, which the meter factor then corrects. So the pulse stream sits at the very bottom of the measurement stack, beneath the K-factor and meter factor that everyone talks about - if the pulses are wrong, everything built on them is wrong.
That is why the integrity of the pulse signal matters so much in custody measurement. A dropped pulse means a missed increment of volume that is simply never counted; a spurious pulse from electrical noise means volume that never flowed is added to the total. Neither error announces itself in the volume reading, which looks perfectly normal, so the measurement system needs a way to police the pulses themselves.
The tool for policing pulses is dual pulse output: the meter produces two pulse channels, A and B, with a fixed, known relationship between them - typically a set phase offset. A flow computer that reads both channels can continuously verify that relationship. As long as A and B track each other as they should, the flow computer treats the pulses as trustworthy. When they disagree - a pulse appears on one channel with no matching companion on the other, or the phase relationship breaks - it flags a pulse security fault.
This dual-channel checking catches the failure modes a single channel would silently pass. Electrical noise inducing a spurious pulse tends to appear on one channel but not correctly on both, so the comparison rejects it. A degrading pickup dropping pulses breaks the expected pattern between channels. In effect the two channels cross-check each other, turning silent pulse errors into detected, alarmable events rather than quiet biases in the volume total.
When a pulse security fault occurs, the flow computer can respond in configured ways - counting from the good channel, substituting an estimated rate, and raising an alarm - so the measurement record is annotated rather than quietly corrupted. This is what makes dual pulse the norm for custody-grade turbine and positive-displacement meters: it converts pulse integrity from an assumption into something the system actively verifies.
Pulse fidelity describes how strictly the pulse signal and the checking around it are held to a standard. ISO 6551 defines levels of pulse security, and higher levels demand tighter cross-checking of the dual channels, so that a wider range of faults is detected and the integrity of each counted pulse is more strongly assured. A custody installation is typically specified to a demanding fidelity level precisely because the volume it produces is bought and sold, and the difference between level A and lower levels is essentially how much the system can be trusted to catch pulse errors.
All of this pulse handling happens in the flow computer, which counts the pulses, checks A against B, applies the K-factor, and produces the volume totals. A cloud SCADA platform like Merobix does not touch the raw pulse train - that is a fast electrical signal wired directly to the flow computer. Instead Merobix polls the flow computer and reads out the results and diagnostics it produces: the volume totals, the flow rate, and status flags including any pulse security or fidelity alarm the computer has raised.
Surfacing those status flags is where remote monitoring adds value at the signal layer. A pulse security alarm on a custody meter is a serious event - it means the volume being recorded may be suspect - and seeing it promptly through SCADA lets a technician investigate the wiring, pickup, or noise source before a shift's worth of measurement is called into question. Watching the pulse-integrity status alongside the volume totals ties the number everyone trusts back to the raw signal it actually rests on.
The meter produces one electrical pulse for each fixed increment of volume that passes, so the pulse count is proportional to total volume. A flow computer accumulates the pulses and divides by the meter's K-factor - its pulses-per-unit-volume constant - to convert the count into an indicated volume. The pulse rate also gives instantaneous flow.
Dual pulse means the meter outputs two pulse channels, A and B, with a fixed known relationship between them. A flow computer reads both and continuously checks that they track correctly, so a spurious or missing pulse breaks the pattern and is flagged as a fault. This pulse security catches signal errors that a single channel would silently pass into the volume total.
Pulse fidelity refers to how strictly the pulse signal is verified against a security standard, with ISO 6551 defining levels of increasingly rigorous cross-checking of the dual channels. Higher fidelity means more pulse fault types are detected, giving stronger assurance that every counted pulse is genuine. Custody measurement is specified to a demanding fidelity level because the volume is bought and sold.
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