By using the NI LabVIEW WSN Module to target and customize NI WSN measurement nodes, you can control power usage and data acquisition rates. For many applications, you can increase performance by deploying LabVIEW code to the node that modifies how data is acquired and when radio messages are transmitted to the gateway. However, to achieve increased performance, one must understand the tradeoffs between longer battery life and faster acquisition rates and the necessary increase in code complexity. To learn more about the operation and execution of applications on an NI WSN measurement node, visit LabVIEW WSN - Under the Hood.
2. Power Benchmarks (WSN-3202, WSN-3212, WSN-3226)
By default, WSN nodes are programmed to send all acquired data to the gateway via a radio message at each sample interval. Therefore, when setting the sample interval of the node to one second (1 Hz), the radio on the node is powered up at the same rate. Battery life can be increased by programming the node so data is not transmitted at each sample interval. As can be seen in Table 1, the power savings are significant.
|Battery Life (months)|
|5 Seconds||50 Seconds||24.71|
|5 Seconds||500 Seconds||25.99|
|5 Seconds||5000 Seconds||26.99|
|60 Seconds||60 Seconds||36.0|
Table 1: Battery life achieved through slower transmit rates
Note that a transmit interval beyond 100 seconds has a limited effect on power savings. This is a result of the node’s heartbeat signal which causes the radio to power up and transmit status information to the gateway once every 61 seconds if no radio transmission has occurred in that time period. Therefore, regardless of the transmit interval, the node will power up the radio at least once every 61 seconds to maintain the network connection.
This benchmark tests the power usage savings by programming the node as shown in Figure 1. The sample interval is set in the start case and the transmit interval is programmed by performing a modulus on the number of samples taken and sending back every 1, 10, 100, or 1000 samples. This behavior would be beneficial in a program that is used to average or threshold data samples, cases where data does not need to be returned to the host after every sample.
Figure 1: Power usage test application
Although other factors can influence the battery life of WSN nodes, only the radio usage was investigated in this benchmark, as the radio has the most significant power consumption of all components on the node.
Power Benchmarks (WSN-3230, WSN-3231)
Visit the WSN Serial Node Power and Performance Benchmarks document to learn more about power consumption tradeoffs for the WSN-3230 and WSN-3231.
3. Acquisition Rate Benchmarks
Each WSN measurement node offers different ways to configure the analog front end, resulting in different acquisition rate benchmarks for each configuration. Refer to the benchmark documents below to view node-specific acquisition rate benchmarks.
WSN Serial Node Power and Performance Benchmarks (Coming Soon!)