Vibration sensor selection for rotating machinery monitoring
A vibration sensor converts mechanical oscillation into an electrical signal that can be trended, alarmed on and analysed. On industrial plant, this measurement is the primary input to condition monitoring of motors, pumps, fans, compressors and gearboxes. LOGGON TECH supplies the LOGGON-401 series, a family of triaxial vibration sensors with integrated temperature measurement on selected models, intended for permanent installation on machinery and for use with the LOGGON-400 system and LOGGON-V1 instrument. This page sets out the models in the range, the engineering background behind the specifications, and the points to check when specifying a sensor for a given machine.
Overview of the category and where it is used
A vibration sensor for permanent condition monitoring typically combines a piezoelectric or MEMS accelerometer element, signal conditioning, and a communication interface in a sealed housing. The sensor is bolted or stud-mounted to the machine surface, normally on the bearing housing or close to it, so that the vibration path between the fault and the sensor is short and stiff. Data is transmitted periodically or on demand to a gateway or portable instrument.
The frequency range of the sensor determines which fault types it can observe. Bearing defects and gear mesh problems generate energy at high frequencies, often several kilohertz, while imbalance, misalignment and looseness appear at low orders of running speed. A sensor with a 10–5000 Hz usable band covers both groups, which is why this range is common for general-purpose machine monitoring. Below 10 Hz, mounting resonance and structural compliance limit useful measurement on most machines; above 5 kHz, the sensor must be mounted with high stiffness and good surface contact to avoid attenuating the signal.
Triaxial measurement means the sensor reports vibration in three orthogonal axes from one housing. A single triaxial vibration sensor replaces three uniaxial sensors and three cable runs, and because all axes are measured at the same point, the axis data can be combined into an overall velocity or acceleration value without geometric correction. For a plant buyer, this reduces installation cost per measurement point and simplifies wiring on machines with limited access.
The predictive maintenance sensor concept is background context for this category: a sensor installed permanently on a machine provides repeated measurements under comparable conditions, so trends can be tracked over months and maintenance scheduled before functional failure. The value of the approach depends on stable mounting, a consistent measurement band, and a data path that does not lose samples.
Models in this range
The LOGGON-401 series comprises three models. All are triaxial with a ±16 g peak range and a 10–5000 Hz frequency band. The differences are in temperature capability, manufacturer-published explosion-protection markings, data output and power supply.
LOGGON-401
The LOGGON-401 measures vibration over 10–5000 Hz at ±16 g peak in three axes and also measures temperature from −40 °C to +125 °C. It carries IP67 ingress protection and the manufacturer-published explosion-protection marking Exia IICT4Ga, and is powered by a battery with more than 2 years of service life. The combination of intrinsic safety and temperature measurement makes it suitable for installation in hazardous areas and on machines where bearing temperature is a monitored parameter alongside vibration.
| Frequency range | 10–5000 Hz |
|---|---|
| Vibration range | ±16 g peak, triaxial |
| Temperature measurement | −40 °C to +125 °C |
| Ingress protection | IP67 |
| Explosion-protection marking | Exia IICT4Ga (manufacturer-published) |
| Battery life | > 2 years |
LOGGON-401B
The LOGGON-401B provides ±16 g triaxial measurement over 10–5000 Hz and outputs acceleration, velocity and spectrum data types. It is battery powered. Its documented data types are acceleration, velocity and spectrum; the spectrum output supports frequency-domain diagnosis of bearing and gear faults.
| Frequency range | 10–5000 Hz |
|---|---|
| Vibration range | ±16 g, triaxial |
| Data types | Acceleration, velocity, spectrum |
| Power supply | Battery |
LOGGON-401D
The LOGGON-401D provides ±16 g triaxial measurement over 10–5000 Hz and uses a rechargeable battery. Its sensor element is rated for −40 °C to +125 °C. The rechargeable supply suits sites where sensors are serviced on a fixed interval and battery replacement is managed as part of a route.
| Frequency range | 10–5000 Hz |
|---|---|
| Vibration range | ±16 g, triaxial |
| Sensor element temperature rating | −40 °C to +125 °C |
| Power supply | Rechargeable battery |
How to select
- Hazardous area status. If the machine is in a classified zone, the published Exia IICT4Ga marking of the LOGGON-401 and LOGGON-401B is the deciding factor; do not substitute a model that does not carry the marking.
- Temperature monitoring. Where bearing temperature trend is required in addition to vibration, the LOGGON-401 provides both from one housing.
- Data output. If the gateway or host system expects velocity or spectrum values rather than raw acceleration, the LOGGON-401B supplies these directly.
- Power strategy. Battery life above 2 years on the LOGGON-401 suits hard-to-reach points. A rechargeable supply on the LOGGON-401D suits planned service routes with defined intervals.
- Frequency band. Confirm that the 10–5000 Hz band covers the fault frequencies of interest. For very low-speed machines, check whether the lowest orders of running speed fall inside the band.
- Mounting. Use a flat, machined surface with full contact under the sensor base. Stud mounting gives the stiffest connection; adhesive mounting is acceptable only where the high-frequency content of interest is limited.
Integration and communication
The sensors are consumed by the LOGGON-400 system and the LOGGON-V1 instrument. The gateway manages up to 64 nodes, so a single gateway covers a machine train or a defined area of the plant. Plan the radio or bus path so that each node has a reliable link; structural steel and dense machinery can attenuate signals, and node placement should be checked on site before commissioning. Data from the gateway is passed onward for trending and alarm evaluation; the LOGGON-410's uplink interface is confirmed per project, while the LOGGON-V1 documents Ethernet with optional 4G. Keep sensor serial numbers mapped to machine tags and measurement positions in the host system; this record is what makes long-term trending usable when sensors are replaced.
FAQ
What does triaxial measurement provide compared with a single-axis sensor?
Three orthogonal axes from one housing. This captures faults that appear predominantly in one direction, such as axial movement on a misaligned coupling, without requiring three separate installations. It also reduces cabling and mounting points per machine.
Why is the 10–5000 Hz band relevant to bearing and gear faults?
Bearing defect frequencies and gear mesh frequencies typically produce energy in the kilohertz region. A sensor band extending to 5000 Hz allows this energy to be measured, provided the mounting is stiff enough to transmit it.
Which model should be used in a hazardous area?
The LOGGON-401, which carries the manufacturer-published Exia IICT4Ga explosion-protection marking. Confirm that the published marking matches the zone and gas group of the installation before ordering.
How many sensors can one gateway handle?
The LOGGON-400 system gateway manages up to 64 nodes. The practical number per gateway depends on physical layout, update rate and the condition of the communication path.
For specification enquiries, state the machine type, operating speed, mounting position, hazardous area classification and the data types required by the host system. These five inputs determine the model choice within the LOGGON-401 series and the integration architecture around the LOGGON-400 system or LOGGON-V1 instrument.