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Which sensors are compatible with vbOnline?

The following sensors are compatible with vbOnline devices:


Measure dynamic acceleration and output a voltage signal. A 4 mA drive current is supplied by the vbOnline device but can be disabled if required. Sensitivity (mV/g) and offset values are essentially unlimited.

Velocity sensors

Measure dynamic velocity and output a voltage signal. A 4 mA drive current is supplied by the vbOnline device but can be disabled if required. Sensitivity (mV/ mm/s or mV/ in/s) and offset values are essentially unlimited.

Displacement sensors

Measure dynamic displacement including DC level (i.e. gap) and output a voltage signal. These are commonly referred to as proximity (prox) probes. The vbOnline device supports sensors with either a positive or negative output. Sensitivity (mV/μm or mV/mil) and offset values are essentially unlimited.

Voltage-output sensors

The vbOnline device supports any type of sensor that has a voltage output e.g. current clamps, temperature sensors, flow meters and load cells etc. The total output swing of the sensor must be compatible with the 20 V input ranges of the vbOnline device (DC 0 V to 20 V, DC -10 V to 10 V, DC -20 V to 0 V, AC +/- 8 V). One notable exception is thermocouples as their raw output voltage is too low to be measured accurately using this input range.

Readings from voltage-output sensors can be either waveforms or spectra (as for vibration readings), or single-value averaged readings (e.g. for a temperature sensor).

The conversion from voltage signal to measurement units uses the sensor sensitivity (mV/unit) and offset (in units). The offset is the measured value that causes a voltage output of 0 V. The values of sensitivity and offset are essentially unlimited.

4-20 mA sensors

Connect these between the + and - inputs, as described in Sensor Types and Connections (page 21). The vbOnline device supports both 2-wire sensors (loop powered) and 4-wire sensors (separately powered). However, in neither case does the vbOnline device supply power to the sensor. In many installations the same 24 V supply can be used to supply both the device and the 4-20 mA sensors.

Speed Sensors

For a typical, basic machine comprising a motor, a coupling and a driven device e.g. a pump, a single speed sensor will be installed. The many vibration sensors on the machine can all obtain the RPM from this one speed sensor.

The Ascent software also provides for situations where a machine includes a gearbox or other fixed ratio drive such as a belt or chain. The two (or more) shafts in the machine will be turning at different speeds but these speeds are all related to each other. As with the basic machine setup, only one speed sensor is required.

Supported speed sensors

The input circuit is very flexible and accepts pulse-train type signals from a wide variety of speed sensors. A few examples are listed below.

Hall effect sensors

These are ideal, providing non-contact sensing of any ferrous target e.g. gear teeth, flange bolts and shaft keyways.

TTL output

Any sensor that outputs a digital (typically 5 V) signal.

Switch output

Any sensor that makes an electrical contact closure but does not actually provide an output voltage.


A separately powered displacement probe that detects a shaft keyway. Its output may need to be conditioned to match the 1.5 V threshold and 12 V max level of the tach inputs.

Optical tachs (LED or laser)

These are compatible but not recommended due to the need to keep optical elements clean.