Spatial resolution is the length of fibre over which a single reported temperature is averaged. Sampling interval is the spacing between consecutive reported values along the fibre. They are different numbers, and confusing them leads to systems that miss the very hot spots they were bought to find.
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Call +86 130 4890 6506 to discuss selection and site conditions Email usA distributed temperature sensing system reports temperature against distance along a fibre. Two parameters describe how finely it does so, and they are not interchangeable.
Spatial resolution is the averaging length — the extent of fibre whose temperature contributes to one reported value. It is a property of the interrogator's design and of the pulse it sends. Think of it as the size of the window the instrument looks through. Datasheets often quote it instead as the length over which the instrument's response rises from 10% to 90% of a step change; that is the same property described from the other side.
Sampling interval is the spacing between reported points — how far apart consecutive values sit along the fibre. It is a setting, and it is usually much finer than the spatial resolution. Reporting a value every half metre does not mean each value describes only half a metre of fibre.
Both are usually quoted in metres, which is exactly why they get conflated. They are also independent: a finer interval does not sharpen the measurement, and a coarser one does not blur it.
Temperature accuracy is a different axis entirely: how close a reported value sits to the true temperature. A system can be accurate and coarse, or fine and less accurate. They are specified separately and they fail in different ways.
Measurement time is the third parameter in the same trade-off. A longer averaging time generally buys a better signal-to-noise ratio, which can support a finer resolution or a more accurate result. Resolution, accuracy and measurement time are chosen together, not independently.
Sampling interval is sometimes called the sampling resolution. Prefer "sampling interval" — the word "resolution" already means the averaging length, and using it for both is how the confusion starts.
"The data points are close together, so the resolution must be fine." No. How closely the output values sit together is the sampling interval. The resolution is the averaging length, and it is usually the larger number — but the two are independent: the interval is a setting, the resolution is not, and an interval coarser than the resolution is perfectly possible. A hot spot shorter than the averaging length is smeared across the reported values around it: it appears wider and cooler than it really is.
"A finer sampling interval gives a sharper picture." It gives more numbers, not more detail. Interpolating between values that are already averaged does not recover information that the averaging removed. Buying a smaller sampling interval and expecting finer detection is a common and expensive mistake.
"Resolution matters most for long routes." It matters most where hot spots are short: a localised defect at a joint, for example. Over a long route where the question is a slow regional rise, a coarser resolution is often perfectly adequate — and buys measurement time or accuracy in exchange.
"Resolution is a software setting." It is not. The averaging length is fixed by the interrogator's optical design and cannot be sharpened afterwards. Software can filter, smooth or interpolate, but it cannot undo averaging.
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Get the resolution right when the thing you must detect is physically short relative to the route — a joint, a termination, a localised hotspot. Ask what the shortest defect you must not miss looks like, and specify the averaging length against that.
Worry about it less when the requirement is to see a gradual or regional rise over a long span, or to trend a route's behaviour over time. There, absolute detection of a small local feature is not the job, and a finer resolution can cost measurement time you would rather spend elsewhere.
Spatial resolution is the length of fibre averaged into one reported value. Sampling interval is the distance between reported values. The interval is usually much smaller than the resolution, which is why a fine data spacing can coexist with a coarse measurement.
Because it is averaged with the cooler fibre on either side of it. If the hot spot is shorter than the spatial resolution, its contribution is diluted across the whole averaging window, so the reported rise is smaller and wider than the real one. This is a property of the measurement, not a fault.
No. Averaging happens in the optical measurement, before any software sees the data. Interpolation can make a plot look smoother, but it cannot restore detail that was averaged away.
Start from the defect. Decide the shortest hot spot you must not miss, and that sets the upper bound on the averaging length. Measurement time then follows from the resolution and accuracy you need, and is usually the parameter you negotiate.
No. It produces more data points and more storage and processing for no additional real detail. Choose the interval that makes the profile convenient to work with, and spend the effort on resolution instead.
They are separate properties. Resolution governs how finely the temperature is resolved along the fibre; accuracy governs how close each value is to the truth. A system can be good at one and weak at the other.
If you need to work out what resolution your route actually requires, describe the shortest defect you must not miss and the span it sits in. We will tell you what that implies for the specification — including whether a coarser setting would do.
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