One of the best ways to measure flow using a weir or flume is to use a staff gauge. This low-tech solution is reliable and cost-efficient provided it’s applied correctly. Even then, however, there are still a few factors that can throw off your measurements. Learn about the most common staff gauge measurement errors, so you know what to avoid with your readings.
Turbulence
If you’re dealing with a flow that’s particularly turbulent, a staff gauge isn’t going to be able to offer accurate readings. The water level elevation will be constantly rising and falling, so you must apply the staff gauge within a stilling well. These wells will steady the water level to a single point from which you should take your measurement. Just make sure it’s sized properly to avoid stilling-well lag.
Subpar Cleanliness
Among the more obvious errors, you’ll find the issue of cleanliness. Oftentimes, flow through weirs and flumes can be particularly dirty, and that dirt, along with other sediment and debris, can get caught on the staff gauge. When that happens, the numbers and marks on the gauge may be illegible, which defeats the entire purpose of using it to measure.
Excessive Gradations
While it may seem that the more lines you have on your staff gauge the better, that’s not actually the case. There comes a point where the measurement marks are indistinguishable from any reasonable viewing distance, making the measurement harder to determine and harder to read in general. In fact, these gradations can make measurements worse even if you’re just trying to look at the levels in groups rather than a massive collection of individual marks.
Illegible Design
Not all staff gauges are created equal. They come in a variety of different sizes that each work best for a specific kind of flume or weir. For example, you can use a precise gauge with small number marking when measuring a calm and clear flow. If you’re dealing with excessively turbulent flow, however, larger number markings are going to be more beneficial. Additionally, it’s helpful to opt for a gauge that uses contrasting colors for the numbers and the background. Black numerals on a background of bright yellow is a common winning combination in that regard.
Poor Placement
The physical location of the measurement is only satisfactory if it’s both in the right place in accordance with the weir or flume design and is in accordance with your line of sight. If you’re looking down on the gauge from a higher perspective, for example, it’s far more difficult to determine the actual measurement than if you’re looking at it straight on.
Find Staff Gauges With Tracom
If you’re looking for a staff gauge you can count on, Tracom is always happy to help. Our team will work with your unique circumstances to help you avoid the common staff gauge measurement errors. Check out our collection of staff gauges designed for easy measurements, and contact us to learn more about everything we have to offer.
