FAQ

Domanda 1: What is the core transmission technology employed by Sensicast?
Risposta: At 2.4GHz, SensiNet supports IEEE 802.15.4 radios (which are Direct Sequence Spread Spectrum radios) with frequency hopping modulation techniques applied as well. The result is a point-to-point radio communication that has proven 100% effective in power plants, steel mills and other harsh RF environments.

Domanda 2: Do Sensicast products require a license?
Risposta: No. Products offered by Sensicast operate in the internationally licence-free 2.4 GHz Industrial, Scientific and Medical (ISM) frequency band.

Domanda 3: What kind of range can be expected?
Risposta: Actual range in any radio application is dependent on the implementation environment. However as a general guide for planning purposes we now are confident that we can usually achieve up to 70 metres between nodes inside a typical industrial or commercial building not in direct line of sight and up to around 200 metres outside in direct line of sight.

Domanda 4: Why not use 802.11 compliant (WiFi) protocols?
Risposta: The 802.11 'WiFi' protocol standard (2.4GHz) was designed primarily to promote LAN-based product interoperability and is best suited to this application. All 802.11 variants are optimized for high speed/short range communications and are generally not suitable when the needed range exceeds a maximum of 60 metres indoors. The only way to extend the range of 802.11 devices is through specialised antennas or additional base stations and special wireless repeaters which increase cost and complexity. 802.11 is primarily used for TCP/IP traffic on Ethernet connections which requires that all devices have a unique IP address. This is time consuming to set-up and manage in larger networks. Also, 802.11 employs only DSSS (see below) and is not very resistant to interference from all sources including Bluetooth radios and general electro-magnetic interference. 802.11 protocols are designed for file transfer and data streaming and as such represent a much greater security risk. Since wireless process sensors normally need very low intermittent data rates the manageability, security risks, cost, limited range, unreliability and complexity of 802.11 outweigh any potential advantages.

Domanda 5: How does mesh networking differ from Bluetooth?
Risposta: Bluetooth is a single-hop point-to-multi-point technology designed for and mainly targeted at ad-hoc short range cable replacement applications such as wireless keyboards and mobile phone hands free operation. It is also quite limited in scalability with the number of network devices it can support per network limited to 8. There are some industrial applications where Bluetooth and/or other wireless technologies are applicable and it is part of Sensicast philosophy to be led by the needs of the application and not to try and make a particular technology fit a problem if it is not appropriate.

Domanda 6: Security is currently a major concern with IT wireless (WiFi) networks – how do wireless sensor networks address this issue?
Risposta: The designers of the underlying technology standards used in wireless sensor networks (IEEE 802.15.4) were fortunate in being able to address security as part of the design specification rather than having to tackle security retrospectively. As such, the 802.15.4 radio standard builds in AES 128-bit encryption for all traffic. Also, the limited data rates supported by 802.15.4 networks are really not suitable for hacking or eavesdropping activities. It is also possible to lock 802.15.4 radio networks once they have been set up to prevent new devices joining.

Domanda 7: As this is a new technology should I not wait until the protocol standards issues are resolved before adopting the technology ?
Risposta: Although there are several alternative wireless sensor networking protocols marketed by different companies and alliances they all use the IEEE 802.15.4 radio protocol as their foundation and any future standards will also be compliant with 802.15.4. It is therefore very important that any wireless mesh sensor networking hardware is fully compliant with 802.15.4 so that future standards may be adopted. Because of the breadth of the applications for the technology it is very likely that no one 'standard' will meet all needs since they all are a trade off between different performance factors. Devices will likely be offered with the variant of the standard that is most suitable for the intended application. For example, the domestic market needs low cost whereas the industrial market generally demands higher reliability so protocol standards designs have to reflect this. The dominant body in industrial wireless sensor networking standards development is the US Industrial Systems and Automation society (ISA) whose SP100 committee and associated working groups are currently working through this issue. It is to be hoped that standards will become available probably in 2008. Devices supplied by Sensicast will support the standards when they are available. In the meantime there is tremendous business value to be gained by use of the best available wireless sensor network protocols, such as SensiNet.

Domanda 8: What is Distributed Frequency Spread Spectrum (DFSS)? How is it different from Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS)?
Risposta: DFSS is the approach that Sensicast has developed which essentially combines the FHSS and DSSS techniques.  We utilize an 802.15.4 radio which natively utilizes DSSS.  This means that the transmitted information is spread across a number of frequencies simultaneously.  This technique is inherently immune to narrowband interference but can be swamped by interference that is more broad-band in nature.  Frequency Hopping (FHSS) is much more resistant to broad-band interference but in the event of interference in a given channel will require a retransmission which adds some latency.  Sensicast's patented combination of FHSS on top of DSSS (DFSS) provides good first transmission success but can follow-up with a retransmission in a different frequency channel if narrow-band interference or multi-path fading prevents success on the first attempt. DSSS is implemented in the PHY layer. SensiNet has proprietary MAC and Network layers which incorporate our Frequency Hopping algorithms.

Domanda 9: What are the power input options and power requirements of the Mesh node?
Risposta: The average current draw for the MESH node is 40ma with short peaks of 80ma. The input can be 7.5 to 30VDC or 12 to 24VAC into pin 1 and 2 of the green terminal strip or 5 to 7.5 VDC through the barrel connector.

Domanda 10: What are the power input options and power requirements of the Bridge node?
Risposta: Same as the mesh node unless the Ethernet connection is being used in which case add another 80mA. Therefore maximum 160 mA. The input can be 7.5 to 30VDC or 12 to 24VAC into pin 1 and 2 of the green terminal strip or 5 to 7.5 VDC through the barrel connector.

Domanda 11: How should power be connected to the Mesh and Bridge node green terminal strip?
Risposta: They are numbered 1, 2 ,3 from RIGHT to LEFT looking at the front of the node. Pins 1 and 2 are not polarity sensitive. AC or DC can be connected between either pin. Pin 3 mimics the barrel connector with the positive voltage going to pin 3.

Domanda 12: Are Sensicast products RoHS compliant?
Risposta: 5th July 2006. Yes we are aware of the RoHS legislation.  We believe that our products fall into the Control and Monitoring class and as such are exempt.  However we have taken steps to become compliant as there are similar initiatives in California and we suspect that the EU will eventually move to close the Control and Monitoring exemption. The next build that we request from our Contract Manufacturer will be RoHS compliant, however we have inventory on hand that we will be looking to expend before we create more.  When we ship RoHS compliant product we will provide a self-certification of compliance.

Domanda 13: What interfaces are possible to the OEM module?
Risposta: The only currently implemented interface is I2C. A variety of others are possible, including UART and SPI.

Domanda 14: Do the bridge node and gateway support PoE?
Risposta: The bridge node does not and there are no plans to add it. The Gateway should support PoE in a future release.

Domanda 15: What is the behaviour of OPC Server data if a node stops reporting?
Risposta: The NodeState parameter and the DataQualityBad indicator will not change before 6 minutes have passed if a single node goes offline. The OPC Server will only ever represent data that was actually sampled by a node.  Every OPC data reading comes complete with an address, a quality, a timestamp, and the data value.  No new readings will be represented in the OPC Server (i.e. with a new timestamp) before the 6 minutes expire.  The OPC Server will continue to display the last reported reading. Thus if you want to be assured of values being 'current' you would need to have your software compare the timestamps of the most recent reading and the previous one. If they are the same the node has not reported in and may have a problem.

Domanda 16: What are power requirements of OEM200 module?
Risposta: Using the cycle asleep--processing--transmit--processing--receive--asleep the current draw at 3V is Transmit = 100mA for 3ms Receive = 40mA for 2ms. Processing = 4 mA for approximately 40 ms. Asleep = 20 uA for heart beat Note that processing involves accessing the i/o card for required data, etc and will depend upon the application to some extent. This figure is typical for the Sensicast ALOG and RTD sensing nodes.

Domanda 17: To which applications have Sensicast systems been integrated using OPCServer and what was the usage?
Risposta: We have integrated with the following applications through OPC: Wonderware – used by several customers for temperature monitoring Iconics Genesis32 – no deployed applications yet, but tested and works very well LabView – used by several customers, including GE Energy for temperature monitoring Intellution – used by GE Kaye to provide FDA 21 CFR Part 11 validated monitoring systems CitectSCADA – deployed at Hollingsworth and Vose for compressed air monitoring Excel – easy way to extract data.

Domanda 18: What is Sensicast's position on battery powered routing nodes?
Risposta: The SensiNet architecture permits the use of reduced duty cycle mesh nodes.  In order to implement this functionality changes will be required to the firmware and to the mechanical design of the Mesh nodes. This functionality is not currently seen as a high priority however this could change with sufficient customer interest. We pretty firmly believe that in order to have industrial class product the infrastructure should be powered.

Domanda 19: If I upgrade Sensimesh software can I retain my old database?
Risposta: Yes, you can retain your old databases.  This happens automatically – just remove the old server and install the new one and you should be all set.  These is still no way to delete node IDs, but you can disable them to make then invisible in the Node Manager and other applications (but not for the SensiMesh Server unfortunately).

Domanda 20: How can I preserve the configuration of my Sensicast system and the data in the database if I change the computer?
Risposta: 1. Copy the following files on the current machine to a safe place off the machine C:\Program Files\Sensicast\Sensicast Protocol Service\EMS.fdb C:\Program Files\Sensicast\Sensicast Protocol Service\VPD.fdb C:\Program Files\Sensicast\Sensimesh Server\SENSIMESH.fdb 2. Install Sensimesh software on the new machine in the normal way. 3. Replace the newly installed files above with the saved versions.

Domanda 21: Do the VOLT nodes have the ability to read negative values - for example a range of +/- 5V?
Risposta: No, they only read positive values.