Fedrel / Clamp-on ultrasonic flow meters
FM21 N
Portable ultrasonic, 0-12 m/s, ±1% accuracy, printed ±3% repeatability, IP54 transmitter/IP68 transducer, 4-20 mA, 2 GB SD storage, 11.1 V rechargeable battery, 5 m cable
Connection and size scope: 25-1200 mm, external clamp-on
MODEL OVERVIEW
What the FM21 N offers
- Connection and size scope: 25-1200 mm, external clamp-on
Manufacturer’s documented description: Fedrel product and price list, effective 20 January 2026, pp. 8, 12, 14. Options and qualifications above are retained as stated.
Check these document differences
Accuracy and repeatability
Fedrel effective 20 January 2026 list p.12: ±1% accuracy
Same entry prints ±3% repeatability; definitions/correction required
Request written confirmation for the offered size and configuration before using either value.
TECHNICAL DATA
FM21 N specifications
| Parameter | Documented value |
|---|---|
| Measuring principle | ultrasonic clamp onFedrel product and price list, effective 20 January 2026, 8, 12, 14 |
| Accuracy statement | ±1%S17 · 13 |
| Connections | Clamp-on; stated pipe-size range 25–1200 mmS17 · 13 |
| Sensor protection | Encapsulated IP68 transducerS17 · 13 |
| Transmitter protection | IP54S17 · 13 |
| Power supply | 11.1 V rechargeable lithium batteryS17 · 13 |
| Included outputs | 4–20 mAS17 · 13 |
| Offline storage and backfill | 2 GB SD card; log format not suppliedS17 · 13 |
| Included accessories | Transducers, handheld device, charger, 5 m cable, chain, railing and coupling compoundS17 · 13 |
| Documented size scope | 25-1200 mm, external clamp-onFedrel product and price list, effective 20 January 2026, 8, 12, 14 |
| Repeatability | ±3% printed; anomalous relative to accuracy, obtain clarificationS17 · 13 |
| Flow velocity range | 0–12 m/sS17 · 13 |
Details to confirm for the offered configuration
These parameters are not established as exact-model values in this record. Some may not apply to this technology.
- Q1 m3 h
- Q2 m3 h
- Q3 m3 h
- Q4 m3 h
- Working pressure and temperature
- Approvals and scope
DUTY & SELECTION
Where to consider this type
Sensors mount outside an existing pipe. This can avoid cutting the line and keeps the sensors out of contact with the water. Honeywell clamp-on overview
Installation and commissioning
Before the meter is selected
- Actual OD, wall thickness and lining
- Fluid and pipe acoustic suitability
- Coupling, mounting access and full pipe
- Signal-quality demonstration and intended acceptance
Before the system is handed over
- Confirm the installation drawing, orientation and access for service.
- Match the actual flow range and permitted pressure loss to the project.
- Record meter serial number, start reading and any output scaling.
- Commission communications against the receiving system and retain the test record.
Reading and communication
Documentation mentions: 4–20 mA. These may be optional or specific to a variant.
Discovery tags come from the documented description, including optional capabilities. Confirm inclusion and exact size/configuration.
A connected metering system is five parts: meter → interface or module → network or gateway → software → billing, dashboard or control system. A quotation should name who supplies and maintains each one. AMR-ready equipment may still require separately quoted radio, gateway, head-end and billing software.
Understand pulse, wired and wireless reading ↗Documents and purchase checks
Read the Fedrel technical reference → · Browse the source index
Source: Fedrel product and price list, effective 20 January 2026, pp. 8, 12, 14. Reviewed 2026-09-09.
Ask for these before ordering
- Approved drawing for the exact model, size and configuration
- Serial-number calibration or factory test record
- Applicable approval certificate and exact scope
- Installation manual and required straight pipe
- Protocol/register map and output power requirements
- Option/accessory codes with included components
- Pressure-loss curve, flange drilling and face-to-face length
- Current written commercial and warranty terms
SPECIFY YOUR REQUIREMENT
Get a quotation for FM21 N
Tell us the size and quantity you need. Add the fluid, flow or output requirement if known. You can review and send the enquiry from your email app on the next page.