composition resistors

Power Metal Film Flame-Proof Resistors (FMF)

Direct Electronics is a global engineering electronics supplier for performance-critical applications, introducing the (FMF) series of Power Metal Film Flame-Proof Resistors. Offering a combination of high precision and handling high power conditions, this resistor is ideal for measuring power line voltage for power condition and energy metering monitoring.

Direct (FMF) Flame-Proof Resistor is desogned to provide an alternative options between Power Metal Oxide Resistors (RSS, RSN) and Precision Metal-Film Resistors (MF). The (FMF) takes the power handling with flame-proof advantage of metal oxide resistors and inherits the precision tolerance of (MF) metal film resistors to provide a solution for customers looking for an industrial grade flame-proof resistors.

The power of Flame-Proof Resistor (FMF) is rated at 1/4, 1/2WS, 1/2W, 1W, 2WS, 2W, 3WS, 3W, 5WS, 5W, and 7WS respectively. Standard values from 0.1Ω to 10MΩ are available, E24, E-96, and E-192 nominal standard series provides adequate "‘close value match" choice for designers. Maximum overload voltage specifies up to 1000V at 5W normal size or 7WS minimum size.

The (FMF) resistors have excellent high power characteristics to improve reliability and reduce faults. With precision levels of ±0.1% resistance tolerance and ±15ppm/°C TCR they free up designers’ error budgets, enabling savings elsewhere in the circuit. Accuracy is ± 0.1%, ± 0.25%, ± 0.5%, ± 1%, ± 2%, and ± 5% precision tolerance, which saves the designer's error budget and free up other parts of the circuit.

Structurally the resistors include a homogeneous sputtered metal alloy film on a high-aluminum ceramic rod and protect with flame-proof coating. The resistance value in the film was adjusted to the final value by laser spiral cutting. The terminals on both ends of the resistor are covered with a pure tin coating to avoid aging the contacts and a low melting point solder can be used thereon.

Download Metal Film Non-Flammable Resistor (FMF) in PDF.

Features :
  1. High power in small packages, Low electrical noise.
  2. Outstanding stability under a wide range of electrical and environmental stresses.
  3. Pure tin plating provides compatibility with lead (Pb)-free and lead containing soldering processes.
  4. Compatible with “Restriction of the use of Hazardous Substances” (RoHS) directive 2011/65/EU.
Applications :
  1. Ballasts, Amplifiers, Power Supplies, Telecommunications
  2. Household Appliances, Automotive, Computer, Precision Controls
  3. Test Equipment and Instrumentation, Medical Equipment, Security Monitoring
Specifications & Dimensions (Unit: mm) (FMF)
Specifications & Dimensions (Unit: mm) (FMF)
Specifications & Dimensions (Unit: mm) (FMF)
Dimensions (Unit: mm) Operating Temp. Range (℃) Max Working Voltage (V) Max Overload Voltage (V)
Normal Mini L D H d ± 0.1 Normal Mini Normal Mini
1/4W 1/2WS 6.3±0.5 2.3±0.3 28±2.0 0.55 -55 ~ +155 300 200 500 400
1/2W 1WS 9.0±1.0 3.2±0.5 26±3.0 0.65 350 250 600 500
1W 2WS 11.5±1.0 4.5 ±0.5 33 ±3.0 0.78 350 300 700 600
2W 3WS 15.5±1.0 5.0±0.5 32±3.0 0.78 350 350 700 700
3W 5WS 17.5±1.0 6.5±0.5 35±3.0 0.78 500 350 1000 700
5W 7WS 24.5±1.0 8.5±0.5 35±3.0 0.78 600 500 1000 800
The maximum value of D.C. voltage or A.C. voltage (commercial frequency effective value) capable of being applied
continuously to resistors at the rated ambient temperature. Rated voltage shall be calculated from the following formula.
However, it shall not exceed the maximum working voltage.
Rated Voltage (RCWV) = √Rated Power (W) x Nominal Resistance Value (Ω)
Resistance & TCR Range (FMF)
Style Tolerance(%) TCR (ppm/℃)/ Ω
Normal Mini ±15 ±25 ±50 ±100 ±200
1/4W 1/2WS ±5%         0.1Ω~10MΩ
±2%         0.1Ω~10MΩ
±1% 10Ω~1MΩ 10Ω~10MΩ 10Ω~10M 0.1Ω~10MΩ 0.1Ω~10MΩ
±0.5% 10Ω~1MΩ 10Ω~10MΩ 10Ω~10M 0.1Ω~10MΩ  
±0.25% 10Ω~1MΩ 10Ω~1MΩ 10Ω~1MΩ 0.1Ω~1MΩ  
±0.1% 10Ω~1MΩ 10Ω~1MΩ 10Ω~1MΩ    
1/2W 1WS ±5%         0.1Ω~10MΩ
±2%         0.1Ω~10MΩ
±1%   10Ω~1MΩ 10Ω~10MΩ 0.1Ω~10MΩ 0.1Ω~10MΩ
±0.5%   10Ω~1MΩ 10Ω~10MΩ 0.1Ω~10MΩ  
±0.25%   10Ω~1MΩ 10Ω~1MΩ 0.1Ω~1MΩ  
±0.1%   10Ω~1MΩ 10Ω~1MΩ    
1W 2WS ±5%         0.1Ω~10M
±2%         0.1Ω~10M
±1%   10Ω~1MΩ 10Ω~10MΩ 0.1Ω~10MΩ 0.1Ω~10M
±0.5%   10Ω~1MΩ 10Ω~10MΩ 0.1Ω~10MΩ  
±0.25%   10Ω~1MΩ 10Ω~1MΩ 0.1Ω~1MΩ  
±0.1%   10Ω~1MΩ 10Ω~1MΩ    
2W 3WS ±5%         0.1Ω~10MΩ
±2%         0.1Ω~10MΩ
±1%   10Ω~1MΩ 10Ω~10MΩ 0.1Ω~10MΩ 0.1Ω~10MΩ
±0.5%   10Ω~1MΩ 10Ω~10MΩ 0.1Ω~10MΩ  
±0.25%   10Ω~1MΩ 10Ω~1MΩ 0.1Ω~1MΩ  
±0.1%   10Ω~1MΩ 10Ω~1MΩ    
3W 5WS ±5%         0.1Ω~10MΩ
±2%         0.1Ω~10MΩ
±1%       0.1Ω~100KΩ 0.1Ω~10MΩ
±0.5%       10Ω~100KΩ  
5W 7WS ±5%         0.1Ω~100KΩ
±2%         0.1Ω~100KΩ
±1%       0.1Ω~100KΩ 0.1Ω~100KΩ
±0.5%       10Ω~100KΩ  
* Resistance standard decade values E-24, E-96, E-192.
Electrical Performance (FMF)
Test Characteristics Test Methods Performance Requirement
Resistance Measuring points at 10mm±1mm from the end cap. Within regulated tolerance
T.C.R. Room temperature /100°C up. ± 15, ± 25, ± 50, ± 100,± 200ppm/℃
Short Time Overload Rated voltageX2.5 or Max. overload voltage for 5s whichever less. ±(2%+0.1Ω)
Solderability 260°C±5°C, 2s±0.5s 90% Coverage Min.
Terminal strength Direct load: 25N, 10s
Twist test:360°, 5 times
Bending test:5N, 90°, 2 times
No mechanical damages
Moisture resistance 40°C±2°C, 90%~95%RH, 1000Hrs, 1.5Hrs on/0.5Hr off cycle ±(5%+0.1Ω)
Load Life 70°C±2°C, 1000Hrs, 1.5Hr on/0.5Hr off cycle. ±(5%+0.1Ω)
Order Codes (FMF)
Flame-Proof Resistor (FMF) Hot-Spot Temperature
Flame-Proof Resistor (FMF) Hot-Spot Temperature

Derating Curve (FMF)
Non-flammable Resistor (FMF) Derating Curve
Non-flammable Resistor (FMF) Derating Curve
FMF 1/2W 100R J   T52
Part Number
Rated Power (W)
Resistance Value (Ω)
10R 10Ω
100R 100Ω
1K 1KΩ
10K 10KΩ
Resistance Tolerance (%)
J ±5%
G ±2%
F ±1%
D ±0.5%
C ±0.25%
B ±0.1%
C1: ±100ppm/℃
C2: ±50ppm/℃
C3: ±25ppm/℃
C5: ±15ppm/℃
T52 Taping 52mm/Box.
T73 Taping 73mm/Box.
T88 Taping 88mm/Box.