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STS Prepaid Ultrasonic Water Meter XT815-U

The XT815-U is a high-accuracy ultrasonic prepaid water meter fully aligned with the IEC 62055 STS standard. With no moving mechanical parts, an R250 turndown ratio, micro-flow and leakage detection, secure 20-digit TOKEN recharge and intelligent valve control, it is suited to projects requiring precise billing, tighter non-revenue water control and dependable performance in challenging water conditions.

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ADVANTAGE

Key Feature	Customer Value
Wide R250 measuring range	Captures normal demand and very small flows to support complete billing and tighter NRW control.
No moving parts	Ultrasonic transit-time measurement avoids mechanical impeller wear and improves resistance to scale-related loss.
Leakage and empty-pipe detection	Persistent small-flow monitoring identifies possible leakage, while empty-pipe detection protects measurement integrity.
Secure STS prepayment	20-digit encrypted TOKEN recharge helps protect transactions against unauthorized use and tampering.
Intelligent valve control	Built-in motorized ball valve supports low-balance alerts, automatic shutoff and reopening after valid recharge.
Remote management ready	Optional 4G, LoRa or LoRaWAN supports remote reading, configuration and operational reporting.

Core Functions

Ultrasonic transit-time measurement with Class 2 accuracy.
Forward water volume accumulation with local data retention for up to 10 years.
Continuous micro-flow monitoring for potential pipe dripping or leakage.
Empty-pipe detection and automatic suspension of invalid measurement.
Battery voltage monitoring, valve-state detection and valve-stall diagnostics.
Automatic reporting of consumption, fault status and recharge records when communication is configured.

Technical Specifications

Parameter	Specification
Model	XT815-U ultrasonic type
Metering method	Ultrasonic transit-time method
Nominal diameter	DN15 / DN20 / DN25; additional sizes available by configuration
Permanent flow rate Q3	DN15: 2.5 m³/h · DN20: 4.0 m³/h · DN25: 6.3 m³/h
Turndown ratio	R250
Accuracy class	Class 2
Water volume unit	0.0001 m³
Volume resolution	0.001 L
Flow-rate unit	0.001 m³/h
Display	8-digit LCD; value display to 6 decimal places
Static current	≤ 20 μA
Temperature class	T30
Rated water pressure	1.6 MPa
Ingress protection	IP68
Installation orientation	Horizontal (H) or vertical (V)
Power supply	Long-life lithium battery; typical service life 6–10 years
Communication options	4G / LoRa / LoRaWAN
Prepayment protocol	STS (IEC 62055), 20-digit encrypted TOKEN

Typical Applications

NRW management: High-resolution measurement and micro-flow monitoring for utilities focused on leakage and non-revenue water control.

Residential and commercial billing: Secure prepaid water management for apartments, housing developments, offices and rental properties.

Challenging water conditions: A non-mechanical measurement path for projects requiring better resistance to wear and scale buildup.

Ultrasonic Installation Requirements

Critical requirement: Air pockets or an empty measuring section can interrupt ultrasonic transmission and cause zero or inaccurate readings.

Keep the measuring tube completely full; do not install the meter at the highest point of the pipeline.
Standard straight-pipe condition: upstream ≥ 10DN and downstream ≥ 5DN.
With an upstream elbow, tee or valve: upstream ≥ 15DN.
For DN50 and above: upstream ≥ 15DN and downstream ≥ 10DN.
If immediately downstream of a pressure reducer or filter, increase the upstream straight length to ≥ 20DN.
Install an automatic air vent 0.5–1 m upstream and use a downstream check valve where specified.
For vertical installation, water must enter from the bottom and exit from the top.

Customer FAQ

How does prepaid recharge work?

The customer enters a secure 20-digit STS TOKEN. Once accepted, the credit is added and the valve can reopen automatically after a valid recharge.

Why does full-pipe installation matter?

Ultrasonic measurement depends on reliable signal propagation through water. Air or an empty section can interrupt the signal, so measurement may be suspended until the pipe is full.