Features

·	Data Synchronisation within an instrument

·	Synchronisation for instruments across networks

·	Multiple sample rate data synchronisation for groups of instruments on a network

·	Optional GPS Timing Card for improved accuracy

·	Individual Channel Sample rates

Individual Channel Sample Rates

The NetPod 4000 has a global sample rate for which all inputs are sampled together and can be configured to have individual sample rates for each of the individual analogue input channels. The individual channel sample rates can only be set up to the maximum sample rate of the instrument. For example if an instrument is set to operate at 100 Hz then individual channel sample rates can only be to a maximum of 100 Hz.

Network Timing Signals

The NetPod 4000 instruments receive timing signals continually across the network which are generated continually by the PodMng driver software. The PodMng software can use the internal real-time clock of the PC or information from an optional GPS interface card to generate the timing pulses that are sent across the network to all instruments in operation.

The timing pulses are processed within the 4000 units and used to correct the instruments real-time clock in case of drift and so bring the unit back into sync and are sent out approximately 20 times a second.The timing pulses are are sent out regular intervals and the instrument clocks are continually adjusted to maintain synchronisation.

Single Clock Source

Since only a single clock source is used throughout the network to control the data acquisition operations it makes for a very tidy and reliable operations. No external or special synchronisation hardware is required to maintain the reliability of the data readings.

Using the optional GPS interface card the timing pulse will reference the world global clock and can be used to integrate the recorded/processed data to other external applications or instruments.

Network Expansion for Additional Instruments

Any new instruments that are added to a network will automatically be synchronised to the instruments already deployed for measurements.

Introduction

The NetPod 4000 series instruments have been designed from the outset to offer high levels of data synchronisation both between channels within an instrument and instruments across a network

Data Synchronisation Within An Instrument

All of the inputs within a NetPod 4000 are fully synchronised synchronised together and contain an individual ADC converter, signal conditioning and opto-isolation. Upon making a reading all of the inputs make a reading simultaneously. The maximuim skew between channel readings is less than 10 ns.

Network Data Synchronisation

The NetPod 4000 series instruments supports network synchronised data acquisition operations in that all channels, for all instruments on a network can be synchronised together. The synchronisation ensures that all of the individual analogue converters for each input channel for all instruments set at the same sample rate operate together to make there readings at the same instance in time.

The networked synchronised readings are accurate to within a few microseconds. Different groups of instruments can be run across a network at different sample rates and yet still be synchronised together.

Multiple Sample Rate Synchronisation

The NetPod 4000 instruments allow multiple sample rates between instruments on a network. All instruments set at the same sample rate will be synchronised. For example a network containing a series of instruments operating at 100 Hz and 20 Hz will have all instruments at 100 Hz synchronised together and all instruments at 20 Hz synchronised together.

Example System

The image above shows 3 groups of NetPod 4000 instruments deployed on a fibre optic network. Each of the separate groups of instruments can be set to run at different sample rates. All instruments grouped together and running at the same sample rate will be synchronised together.

The network timing packets are sent out automatically across the network to each instrument. The timing packets can be derived from the PC clock or optional GPS Interface card for absolute accuracy.

For example with a sample rate 100 Hz for the 1st group of instruments, 50 Hz for the 2nd gruop of instrument and 10 Hz for the final group. All the 100 Hz instruments will be synchronised together, all of the 50 Hz instruments with synchronised together and finally all of the 10 Hz instruments will be together

Systems Flexibility

The synchronisation operations of the 4000 series instruments is very flexible. Instruments set at the same sample rate but not grouped together on the same network can also be synchronised. The only limitation is that the instruments only receive timing pulses from the same data acquisition PC