Digital guide
You are here:
YOKOGAWA NFLR121-S01
Product Overview:
The NFLR121-S01 is a plug-in type noise filter manufactured by Yokogawa Electric Corporation. It is specifically engineered to eliminate high-frequency noise and electromagnetic interference (EMI/RFI) superimposed on analog signal transmission lines, particularly 4–20 mA DC current loop signals. The S01 suffix designates the plug-in (S-type) mounting configuration, enabling direct insertion into DIN rail terminals or junction boxes without additional wiring.
Detailed content
Technical Specifications:
| Parameter | Value |
|---|---|
| Input Signal Type | 4–20 mA DC (2-wire transmitter loop) |
| Filter Type | Low-pass LC filter |
| Cut-off Frequency | 1 kHz (typical) |
| Attenuation | ≥ 40 dB at 1 MHz |
| Insertion Loss (Pass Band) | < 0.5 dB |
| Rated Voltage | 30 V DC (max) |
| Operating Temperature | -20°C to +70°C |
| Storage Temperature | -40°C to +85°C |
| Housing Material | Flame-retardant Polycarbonate (UL94 V-0) |
| Mounting Method | DIN rail plug-in (S-type) |
| Dimensions (approx.) | 22.5 mm (W) × 97.5 mm (D) × 85 mm (H) |
| Weight (approx.) | 50 g |
| Compliance | CE Marking, cULus (UL listed) |
Functional Features:
- Effective suppression of high-frequency noise (radio frequency interference, switching noise from VFDs/inverters)
- Passive LC filter design — requires no external power supply
- Bidirectional installation — compatible with both input and output sides of transmitter loops
- Compact plug-in form factor — directly inserts into standard terminal blocks
- Maintains signal integrity — minimal insertion loss in the passband ensures accurate 4–20 mA signal transmission
Working Principle:
The NFLR121-S01 utilizes a passive low-pass LC (inductor-capacitor) filter circuit. High-frequency noise components (typically above 1 kHz) are shunted to ground through capacitive elements and blocked by inductive elements, while the desired 4–20 mA DC signal passes through with negligible attenuation. This ensures the control system receives a clean, noise-free analog signal.
Key Advantages:
- Zero power consumption — fully passive design
- Instantaneous installation — no wiring modifications required
- Broad-spectrum EMI/RFI attenuation up to 40 dB at 1 MHz
- UL94 V-0 flame-retardant housing for safe industrial deployment
- Compatible with all 2-wire 4–20 mA transmitters
Applicable Industries:
- Oil & Gas (refinery, upstream, midstream)
- Chemical & Petrochemical Processing
- Power Generation (thermal, nuclear, hydro)
- Pulp & Paper
- Water & Wastewater Treatment
- Food & Beverage
- Pharmaceutical Manufacturing
Installation Requirements:
- Install in series with the 4–20 mA signal loop between the transmitter and the controller/DCS input card
- Ensure proper grounding of the filter housing to chassis ground
- Maintain minimum 10 mm clearance from high-power cables (>100 V AC)
- Verify voltage rating does not exceed 30 V DC across the filter terminals
Usage Precautions:
- Do not use with voltage signals (0–10 V, 1–5 V) — this unit is exclusively for current loop signals
- Do not exceed rated voltage of 30 V DC
- Avoid installation in environments with direct exposure to corrosive gases or liquids beyond IP20 rating
- Do not disassemble — internal LC components are sealed and non-serviceable
