The measurement load defines the relative amount of time the instrument actively collects data. It specifies what percentage of the maximum number of pings per average interval the instrument will use going from 1% to 100% (always in active mode).
A 100% measurement load means that the instrument pings as fast as it is able to. Consequently, a measurement load of 50% means that the instrument pings at half that rate. For example, an 1000 kHz Signature has a maximum internal sampling rate of 16 Hz, which means that each beam will ping 16 times each second. A lower measurement load thus allows the Signature to spread out its averaging interval over a longer period of time as it save battery by going into a lower-power wait state during part of each second. The maximum internal sampling rate for each specific instrument can be found in the instrument technical specifications.
If the Auto measurement load option is enabled, the software automatically selects a measurement load that, with the current settings, targets a velocity precision of 1.5 cm/s.
Effects of variations in Measurement Load
From signal theory we know that the more pings there are within an averaging period, the better the estimate of the true value we're measuring will get . A high ping rate will thus reduce the standard deviation. By increasing the measurement load, you can improve the precision of your measurements, but at the expense of battery consumption. By decreasing the measurement load it is the other way around. The exact relationship is shown in the Advanced tab in the Deployment planning menu. Just try and vary the measurement load, click on Apply and watch the change in the Battery utilization (for a specified assumed measurement duration) and the velocity precision. As you will see this is a trade-off between need for precision and need for duration.
Be aware that there is a difference between the midlife instruments (such as Gen1 AWAC and Aquadopps) and Signatures. While the Gen1 instruments minimum have to ping at least once every second, and therefore has a restricted amount of possible measurements loads, the Signatures gives you the opportunity to use whatever measurement load you want and possibly spread the pings out over several seconds. You can therefore easily increase the average interval without this going on the expense of the power consumption. You get an overview over how many pings that are going into the average interval in the Effect tab in the Deployment Wizard.
Updated