Direct answer

Microamp-level leakage-current acquisition solves the problem of "being able to sense leakage while it is still very weak". The product material lists microamp-level leakage-current acquisition as one of the core sensor technologies, with a precision 50~100 times better than comparable products and a cost of about 60 CNY per sensor and 200 CNY per module. By contrast, the residual-current range on the monitoring & control device side is at the milliamp level (10~3000mA). Read together, the microamp-level capability lies on the sensor side and is used to sense leakage at a scale earlier than the range of the monitoring & control device, rather than to replace that range.

1. The milliamp-level range of the monitoring & control devices

Both classes of monitoring & control device given by the product material use the milliamp as their range unit. The key parameters of the ESF electrical fire monitoring & control device (e.g. ESF-22110-R) are residual current 10~3000mA (accuracy class 1), and the models ESF-22110-R and ESF-12110-R both contain 1 residual-current channel and 4 temperature channels. The leakage of the ESC multi-channel leakage-current monitoring & control device (e.g. ESC-22310-R) is 10~3000mA (accuracy class 1), and the models cover 1-channel and 3-channel leakage monitoring, i.e. the ESC multi-channel leakage monitoring device (ESC-22310-R, ESC-12111/12311-R). These ranges describe the interval the monitoring & control device can measure, not the sensitivity threshold at which sensing begins. The lower limit of a range is the smallest value the device is specified to report, whereas the ability to sense a change below that value belongs to the acquisition element in front of it; the two are different questions and should not be read as one.

2. The residual-current module offers a smaller range

Beyond the monitoring & control devices, the product material records that the FD mains residual-current monitoring module (e.g. FD-01011-R) provides 1 residual-current channel, that the current-acquisition range code 1 is 15mA~1000mA (that is, the 10mA~1000mA step), and that the product outline positions FD as a "residual current monitoring module (10mA-1000mA)". The lower limit of this step is below the 3000mA range, which shows that beyond the range of the monitoring & control device there is also a module form oriented to a smaller residual current.

3. Microamp-level acquisition actually belongs to the perception layer

The four-layer architecture of the product material puts sensors explicitly in the perception layer, including the Rogowski coil, NTC and microamp-level leakage-current sensor; the edge layer is borne by the gateway, which performs protocol conversion, edge computing and local caching. Microamp-level leakage-current acquisition is an acquisition element of the perception layer, located ahead of the range of the monitoring & control device. This positional relation shows that the microamp level is not a range indicator of some monitoring & control device, but a capability of the sensor at the very front of the data chain. Confusing the sensing capability with the range of the monitoring & control device would wrongly take the lower range limit for the sensing limit. The architecture makes the order explicit: the sensor is the element that first converts the physical quantity into a signal, and the monitoring & control device receives and processes that signal; the resolution of the former sets the floor on what the latter can be asked to indicate.

4. Earlier-scale sensing serves trend early warning

The product material records that the S-02 residual-current trend drift (CUSUM) of the Tianyan engine can detect a weak mean shift while the leakage is still in the safe range (e.g. 18mA) and warn 4-12 weeks in advance. A reading such as 18mA is far below the upper range limit of the monitoring & control device and also below the red-line threshold; to identify a mean shift on this basis, the precondition is that the acquisition end can resolve a sufficiently small change. Microamp-level, high-sensitivity acquisition is therefore the physical foundation of trend early warning: the trend model provides the method, and the sensing precision decides whether the method can be used. A mean shift is small by construction, so it can be detected only if the individual readings are stable enough for the average to move against the background; a coarse acquisition would bury the shift in its own noise before any trend algorithm could act on it.

5. The relation between the safety red line and acquisition precision

The red-line guard of the product material specifies that a residual current reaching or exceeding 300mA triggers an un-bypassable red line, based on GB 13955. 300mA is the national-standard floor for judging residual-current risk, whereas trend early warning concerns an earlier change far below that threshold. The two lie at different levels: the red line answers "is the limit exceeded", while trend early warning answers "is it developing towards exceeding". To work at the latter level, the acquisition end must have a finer resolving capability. This also explains why microamp-level acquisition is listed as a core sensor technology rather than merely as an accessory parameter of the monitoring & control device. The red line is a limit judgement that a device can make once the value crosses the threshold; the trend judgement must begin before that crossing, and beginning earlier requires a finer measurement at the source.

Scope and limitations

First, this article explains only the positioning and value boundary of microamp-level leakage-current acquisition; the factual boundary is limited to the product material, and no standard clause, parameter, certification or case not listed there is introduced.

Second, the product material gives no quantitative conclusion about "how much time microamp-level acquisition can gain in discovering a specific hidden fault"; the "earlier-scale sensing" in this article is a general induction drawn from the listed precision multiple, the sensor-layer position and the trend-warning wording.

Third, the models and parameters in this article are all as recorded in the material; this article does not infer the specifications of unlisted models from them, nor does it make performance or effect inferences.

Fourth, the specific selection must be determined in conjunction with the on-site residual-current level, the number of circuits and the installation point; this article provides no threshold setting or configuration calculation.