The LCF-501 series of Force-balance accelerometers were developed as a transparent counterpart to the LCA-165, possessing the same range options, power requirements and form factor; additionally, the 501 series possesses improved performance due to the designs of the new standardized force-balance module: the J-301. This torquer type makes use of taut-band torsional suspension, rather than the traditional pivot & Jewel suspension found in models like the LCA-165.
In addition to taut band suspension the LCF 501’s J301 torquer module is filled with silicone damping fluid, which attenuates unwanted high frequency vibrations up to -6dB per decade, this works by dampening oscillatory motion of the moving servo system encouraging stable operation. The result of these improvements yields a rugged, high performance and high accuracy accelerometer. Fluid-filled torquers are business as usual for Jewell instruments, many of our existing force-balance sensors contain oil filled torquer modules, such as the LSOX series of inclinometers and the LCF-3500 triaxial accelerometer series, which along with the LCF-501 have amassed a growing userbase thanks to their robust performance in vibrational environments.
Taut Band Suspension Summary:
Figure 1: A Taught Band based torquer Figure 2: Taut-band module diagram
- Coil of the taut-band suspension mechanism is suspended about the magnet with platinum-nickel bands and allowed to rotate.
- Very low input and relatively low frequencies capability
- Provide superior repeatability.
- Ideal for tilt sensing applications as well as low g acceleration sensing
- Some models without physical damping for cost-sensitive applications that require the highest level of resolution and repeatability are available.
- Most utilize fluid damping, which increases durability by several orders of magnitude. They are the best choice for high accuracy measurements of low inputs in harsh environments or when they must survive exposure to extreme events.
Pivot & Jewell Suspension Summary:
Figure 3: typical pivot and jewel torquer architecture as used in the LCA-165
- Mechanisms use pivots that are attached to the coil and fit into bearings on the frame that allow the coil to rotate about the magnet.
- Have higher input range and frequency response capability than taut-band suspension mechanisms.
- Usually used to measure acceleration over 2g.
CENELEC & AREMA Compliance:
CENELEC, the European Committee for Electrotechnical Standardization and AREMA, the American Railway Engineering and Maintenance-of-Way Association, both have implemented numerous technical and safety standards which many of our products follow.: The LCF-501 is available as a CENELEC & AREMA compliant version, complete with EMI protective components to meet CENELEC & AREMA requirements. We call this the LCF-510-R, where the “-R” denotes Rail. In this case a notable difference is an EMI protective components and filtered output.
Here is a list of CENELEC & AREMA EN standards which Jewell’s -R sensors have been qualified to meet.
LCF-501-1-R Vs LCA-165-1-R: A Specification Comparison:
| Performance | Units | LCA-165-1-R | LCF-501-1-R |
| Input Range | g | ±1 | ±1 |
| Full Range Output (FRO) | VDC | ±5.00 | ±5.00 |
| Bias | mg max | ±10 | ±4 |
| Bias Uncertainty | mg max | 4.0 | 0.12 |
| Output Sensitivity (Scale Factor) | V/g | ±5.00 | ±5.00 |
| Sensitivity tolerance | % max | ±0.5 | ±0.5 |
| Nonlinearity | % Full Scale max | ±0.02 | ±0.02 |
| Scale Factor Temperature Sensitivity | PPM/°C max | ±100 | ±100 |
| Bias temperature sensitivity | uG/°C max | ±180 | ±50 |
| Nominal Bandwidth (-3db Frequency) | Hz | 85 | 85 |
| Output Noise (0 Hz to 1000Hz) | mVrms | 5.0 (broadband 0 – 20kHz) | 5.0 (broadband 0 – 20kHz) |
| Sensitive Axis Misalignment | deg. max | ±0.5 | ±0.5 |
| Resolution, Threshold, Hysteresis | % Full Scale max | 0.0020 | 0.0010 |
| Cross Axis Sensitivity | g/g max | 0.002 | 0.00002 |
| Output Impedance | Ohms | 1 | 100 |
| warm up time | seconds | 0.6 | 0.6 |
| Electrical | |||
| Input Voltage Range, Accelerometer | VDC | ±12 to ±18 | ±12 to ±18 |
| Input Current, Accelerometer | mA max | 25 | 25 |
| Environmental | |||
| Railway Standard | N/A | EN 50155 AREMA 2011 Part 11.5.1 Class 1 | EN 50155 AREMA 2011 Part 11.5.1 Class 1 |
| Operating Temp Range | °C | -55 to +85 | -40 to +80 |
| Storage Temp Range | °C | -60 to +90 | -60 to +90 |
| Vibration (Sine) | N/A | AREMA Sect 11, Part 11.5.1, Para D.4.a | AREMA Sect 11, Part 11.5.1, Para D.4.a |
| Vibration (Functional Random) | N/A | EN 50155:2007, Par 4.1.3 | EN 50155:2007, Par 4.1.3 |
Note: Bandwidth is typically lower as custom output filters are applied at customer request.
As highlighted in the comparison table above, the benefits of the LCF-501 as compared to the LCA-165 are related to bias: output bias, bias uncertainty, and bias temperature sensitivity. In these cases, 501 shows an order of magnitude of improvement compared to the LCA-165’s already outstanding performance. This is due to the taut-band toroidal suspension – which does not experience stiction or other similar phenomenon affecting output stability and repeatability that can be encountered with pivot and jewel models. This means that CBTC-rail applications can further optimize systems to rely on the LCF-501’s output stability from day to day as the units are powered up repeatedly as the recorded output bias can be compensated for, with minimal drift over time and temperature.
Pivot and Jewell torque units require a minimum input force to overcome stiction forces before an output is observed, but since this is not a factor with taut band sensors, the LCF-501 has superior reliability and resolution. The resolution of the LCF-501 is double that of the LCA-165 across the same operating range.
Another benefit of the LCF-501’s design is the ultra-low cross-axial sensitivity which is 0.00002 g/g max, compared to the LCA-165’s spec of 0.002 g/g max.
The LCF-501’s taut band suspension design gives it improved survivability & lifetime performance compared to pivot and jewel architecture. Sufficiently high shocks in the range of 100G’s can cause performance issues and operational failure of pivot and jewel sensors like the LCA-165, however the LCF-501 survive beyond 1000G’s of shock without failure or significant performance issues.
Applications & Customer testimonials:
The LCF-501 series is well established in the world of CBTC rail applications, The series has been successfully used in Metro, Subways, High-speed trains, and Maglev applications. Accelerometers are mostly used when the train is idling or skidding, due to the sensors superior performance when compared to speed sensors and radar. As of 2023, there has been over 1500 sensors shipped to the Chinese Rail market.
Shanghai Fitsco: Metro Rail Application, Taiyuan Line 2, Shanxi, China
LCF-501 series accelerometers have been successfully used to monitor acceleration for the customers CBTC system along with Hall-type velocity sensors.
“We use the servo accelerometer LCF-501 of your company for the measurement of acceleration parameters in the velocity and distance measurement algorithm……The LCF-501 product parameters meets the application requirement of our system, and Jewell Instruments provides timely and effective technical responses” – Edward Yu, Onboard Application Engineer.
Beijing Hollysys Co., Ltd, China
The LCF-501 is used in high-speed rail & metro applications to measure the speed of the train.
“After testing and evaluation Jewell’s accelerometer met the requirements of our control system, Satisfied with performance and quality” – Lin Ying System Senior Engineer, Beijing Hollysys Co. LTD.