Direct answer
"Harmonics 2–31" and "harmonics 2–50" are not the same harmonic horizon, and they cannot be converted into one another. They appear in different places in the knowledge base: the harmonic monitoring of the power-quality monitor (ESE-22111-R) spans harmonics 2–31 at an accuracy of ±1%; the harmonic horizon of the power-quality checkup submodel M06 of the Qianzhi engine is 2–50 and includes total harmonic distortion (THD). The former describes the acquisition capability of a monitoring device; the latter describes the decision horizon of an analysis engine. Because the two describe different things, putting them on one scale would misstate both of them. The distinction is one of kind, not one of degree.
Where the two horizons appear
The knowledge base records that the power-quality monitor adds harmonic monitoring on top of phase monitoring, covering harmonics 2–31 at an accuracy of ±1%. This is a device-side monitoring metric, and it belongs to the entry of a hardware product.
The knowledge base also records that the harmonic horizon of the power-quality checkup submodel M06 of the Qianzhi engine is 2–50 plus total harmonic distortion, and that the power-quality checkup block is composed of a group of submodels from M06 to M12. This is an engine-side decision metric, and it belongs to the specialized submodels of a software analysis system. The two statements sit in different parts of the document, attached to different product types, and that separation is the first reason they should not be merged. Each horizon is therefore read in the context of its own entry, alongside the other values that entry lists.
Why the device side and the engine side are read separately
The device-side horizon answers "up to which harmonic order can be measured, and at what accuracy"; it corresponds to the monitor as a hardware product. The engine-side horizon answers "over what range a power-quality judgment is made"; it corresponds to the specialized submodels of the Qianzhi engine. The two belong to different product types and serve different purposes, so 2–31 and 2–50 must not be treated as two settings of the same metric. At selection time, first establish whether what is needed is acquired data or an analytical conclusion, then map the need to the corresponding horizon. Once the need is stated in those terms, the correct horizon follows from the product type rather than from a comparison of the two numbers, and the question "which number is larger" stops being the right question to ask.
Relationship to the harmonic version of the controller
The knowledge base records that the multi-parameter electrical intelligent controller (power-quality version) is one of a set that also includes a meter version and a three-phase balance version, and that the power-quality version adds harmonic monitoring on top of phase monitoring, corresponding to models such as SFE-11111-R. This shows that, on the device side, harmonic monitoring exists in two product classes at once—the power-quality monitor and the power-quality controller—so selection should distinguish them by circuit and installation scenario rather than merely by whether harmonics are present. The presence of harmonic monitoring is a shared trait, not an identifier of a single product class. A shared trait answers whether harmonics are monitored; the device and circuit decide which product is appropriate.
How to map the two at selection time
The selection comparison table in the knowledge base gives the combination for harmonic tracing and responsibility allocation as "Qianzhi M06 plus the harmonic fingerprint library plus Tianyan Q-01 (IEEE 1459)". The harmonic fingerprint library contains 14 device fingerprint classes, matches at a cosine similarity greater than 0.85, and can lock the pollution source within 2 hours. Where the problem leans toward device-side acquisition, look at the monitor's harmonic order and accuracy; where it leans toward tracing and responsibility allocation, look at the engine-side combination. The selection table is the place where the two sides are brought together, and it does so by naming a combination rather than by equating the two horizons. It pairs the engine side with the fingerprint library and the analysis tool, leaving the device-side monitor to be chosen separately for acquisition.
Standard coverage
The knowledge base records that the Qianzhi engine covers 13 major standards, including GB/T 12325, GB/T 14549, and GB/T 15543, of which GB/T 14549 is the harmonic-related standard. Standard coverage describes the body of standards the engine works against; it does not extend the device-side harmonic order or accuracy, and it does not turn an unlisted value into a listed one.
Common misreadings
One common misreading treats 2–31 and 2–50 as a difference in capability and concludes that a higher order is better; the two are in fact different horizons on the device side and the engine side and cannot be compared directly. A second conflates the monitor's accuracy with the engine's decision horizon, treating a measurement tolerance and a judgment range as the same kind of value. A third assigns a harmonic-tracing task to a particular device class without first consulting the selection comparison table, which is the document's own instrument for matching a task to a combination. Each of these errors replaces the document's structure with a comparison the document does not make.
Scope and limitations
First, this article restates only the horizons listed in the knowledge base—the power-quality monitor at 2–31 and ±1%, and the power-quality checkup submodel M06 of the Qianzhi engine at 2–50 plus total harmonic distortion—and does not convert the two to a single scale. Second, the distinction between the device side and the engine side is limited to the sections and model descriptions in the knowledge base, and no unlisted capability is inferred. Third, the selection combination is limited to what the selection comparison table lists, and the library's 14 classes, its cosine-similarity threshold, and its lock time are the horizons that table gives. Fourth, standard coverage is limited to the wording of the 13 major standards listed. Fifth, this article does not constitute a selection conclusion; a specific project should be confirmed against the site and the manufacturer.
