Frequently Asked Questions
Range is dependent on many factors including transmit power, receiver sensitivity, antenna type, height of antennas, and what is between the receiver and transmitter. SignalFire has an application note on this subject here. In general, we state that the Sentinel-class nodes have a ½ mile range and the longer range nodes (Sticks, A2,...) have a 2-3 mile range. These ranges are without obstructions and with reasonable antenna height. If you can mount the antenna up high, the range could be more. Because data moves from module to module, range can be substantially extended by placing intermediate modules in the system. When moving data by this method, effective ranges of well over ten miles are practical.
The SFRSS Gateway can support up to 240 Modbus® addresses, and therefore 240 SFRSS modules. In other configurations, such as a streaming system, there is no limit to the number of modules that can be supported. The maximum size of the system is determined by the amount of traffic at the Gateway. A very conservative rule of thumb is one message per second, or 80,000 messages per day. For a system that sends data in once every five minutes, a network size of about 300 modules is an effective maximum. For most applications, the availability of outside communications (e.g., Cellular, Satellite, RS485, Ethernet) dictates the Gateway locations and drives the actual number of modules supported. As a practical matter, most of our customer’s installations run between 3 and 75 modules.
The SFRSS-A2, MB, and GW modules use SignalFire’s 300 mW radio with low-noise amplifier. This system has a total link budget of about 135 dB. This is a combination of radio sensitivity, transmit amplifier power, low-noise receiver amplifier, and high-gain antenna. As a general rule, the minimum reliability link between radios should be 5 dB more than the noise floor. Each transmission in the SFRSS reports its Receive Signal Strength Index (RSSI). For the SFRSS-A2, MB, and GW, the limit of communications is reported as approximately -95 dB (this uses the full 135 dB of link budget), so the limit of effective communications would be reached at an RSSI of -90 dB.
It's easy! Using the free SignalFire ToolKit PC application simply configure the network number and network group to match the Gateway. Set check-in time and assign a Modbus address, and you're done. The module will automatically configure itself on the network and start sending data to the Gateway.
The SignalFire telemetry radios are designed for the 900 or 868 MHz ISM bands. This frequency band has longer range and has less channel interference than the other common band – 2.4 GHz.
Yes, the SFRSS system powers the sensor for only a few seconds every time it takes a reading. The sensor is on long enough only to generate a stable reading and is then turned off. Battery life is determined by the sensor's power requirements and how often it sends data in.
No! The SFRSS is self configuring and self healing. The message will get through as long as there is a communications path.
The gateway is powered continuously and stores the most recent data that is sent in from the modules in its network. When the RTU sends a Modbus poll request to the gateway, the gateway responds with the most recent data stored for that module. The data for a particular module will “time out,” if it is not replaced by new data in a timely manner, and that Modbus address will be dropped, indicating that the module is down. In this case, the RTU will time out on the data request for this module’s slave ID.
Probably not. It would be practical to send an infrequent low-resolution image over the network, but it is designed to support applications where a module generates tens of bytes of data on a per-event or on a regularly scheduled basis (a minute to a day).
Many of the SignalFire nodes can power the sensor using an internal battery or Class I Division 1 solar power module. Battery life is highly dependent on the sensor type and check-in frequency as most of the power in the battery is used to power the sensor.
Battery life if dependent on a number of items but most of the energy in the battery is used to power the sensor. Very little is used to power the radio itself. Things that matter to the battery life calculation are: • Sensor current draw • Sensor warm up time • Check-in rate Battery life with a low power sensor can be in the 5-10 year range. If the sensor draws too much power and this makes the battery life too short, SignalFire offers a Class 1 Div 1 rated solar power subsystem that can fully power the sensor all the time.
Yes. The SignalFire system provides a local application layer. The SignalFire system can control remote actuators and it is often used in Remote Shutdown and valve control applications.
Yes. Many SignalFire nodes can be battery powered using an internal battery pack. Battery life depends on the specifics of the application requirements – notable on the power requirements of the sensor and how often the sensor needs to be read. Battery lifetimes of 5-10 years are attainable with many common sensors. SignalFire can customize a system for your application that maximizes battery life.
Yes. SignalFire systems have been used for years in shutdown applications. The CommGuard failsafe timers incorporated into the Remote Shutdown nodes provides the necessary safeguards for this type of system.
A SignalFire gateway can support a maximum of 240 remote nodes. However, it is important that you manage the network for traffic. We recommend a maximum number of nodes be such that an average of one message per second is received by the gateway. So, if you required a check-in time of 1 minute per node, we would want to limit the number of nodes in that network to about 60. In other configurations, such as a streaming system, there is no limit to the number of modules that can be supported. The maximum size of the system is determined by the amount of traffic at the Gateway. A very conservative rule of thumb is one message per second, or 80,000 messages per day. For a system that sends data in once every five minutes, a network size of about 300 modules is an effective maximum. For most applications, the availability of outside communications (e.g., Cellular, Satellite, RS485, Ethernet) dictates the Gateway locations and drives the actual number of modules supported. As a practical matter, most of our customer’s installations run between 3 and 75 modules.
SignalFire interfaces to many types of sensors. These include: Analog (4-20mA/1-5V) Digital (counter, state, frequency) Modbus (RS485) Temperature (Thermocouple, RTD) HART Strain Gauge Turbine Pickup Other custom sensor interfaces We try and support virtually every sensor type found in the oil field. If you have a sensor that has a unique interface, please call us and we can see if we can support it!
The Gateway stores all sensor data in Modbus registers where each node is represented by a Modbus Slave ID. The native interface for the Gateway is Modbus RTU (RS485). Modbus TCP (Ethernet) is available with the addition of the SignalFire Ethernet GW module. Additionally, SignalFire offers a Gateway Output Module that can output analog and digital signals if yoru controller does not have a Modbus interface or you want to keep a legacy wired interface operational and add wireless.
802.15.4 works very well for many higher data rate applications. However, the SignalFire telemetry system is designed specifically for utility applications operating in harsh environments. The SignalFire system interferes less with other devices and will be less susceptible to interference from other devices than an 802.15.4 system operating in the same spectrum. SignalFire also adheres to the relevant standards, which are designed to manage interference, issued by the radio governing bodies (e.g. FCC Part 15).
34 reads of up to 25 registers each.