By increasing the measurement load, the precision in the velocity measurements increase, but alas 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.
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 Aquadopp Current Meter pings 69 times every second, or 23 times for each beam. An 8% measurement load means that it will ping each beam 2 times then go into wait state for the rest of each second. A lower measurement load allows the Aquadopp to spread out its averaging interval over a longer period of time, and it goes into a lower-power wait state during part of each second.
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, (which is called Precision in the Deployment planning menu).