...
The following data is available from the sensor. Each pulse is captured by the VTi21 (sampled at 25KHz) and analysed to determine polarity, suitability of the waveform and the RMS current. The following values can be recorded by the data logger according to standard acquire on change rules. The 4-20mA output is only available for channel 1.
Quantity | Range | Units | 4-20mA | RS485 | Usage | |
|---|---|---|---|---|---|---|
| HVI Current | 0 to 1500 | RMS Current of the pulsed waveform | mA | Core RCM Channels | ||
| HVI Frequency | 0 to 5 | The frequency of pulses | Hz | |||
| Noise Current | 0 to 1500 | The RMS current observed between pulses. | mA | |||
| Pulse Conflict | Digital | Set TRUE if pulses are observed to be bleeding through from adjacent track sections | NA | |||
| Pulse Waveform | 0 to 1500 | If this channel is requested as a capture, the VTi21 will return a high-resolution waveform of the last observed pulse | mA | |||
| Rejection Rate | 0 to 100 | Proportion of pulses that were the "wrong shape". | % | Mpec Development Channels (Not typically useful to customers and should not be pushed to the server.) | ||
| Rejection Reason | 8 bits | Reasons an event was rejected as a HVI pulse. | bitfield | |||
| Sensitivity | 0 to 2621440 | Dynamic change threshold used to identify the start of a HVI pulse waveform | None (scaled ADC reading) |
How it works
A typical HVI circuit schematic is shown below:
...