Can I work with the tool in wet conditions (rain, snow, or heavy fog) or in heavy dust?

Working in wet or dusty conditions is possible, but be aware of limitations

There are two core measuring devices the head unit uses when making measurements, depending on the one that is active:

1. EDM (Electronic Distance Measuring) - also known, simply, as the laser. The total station makes rapid calculations to measure distances by observing the reflections returning back from the laser.
2. Prism Tracking. The total station's prism tracker makes rapid measurement calculations as the telescope receives reflections back from the prism.

Because of this technological behavior, anything that inhibits the path of reflections back to the head unit, regardless of whether you are using a laser or prism tracker, could cause errors or failures in measurement.

How does wet or dusty conditions affect layout?

Remember that anything inhibiting the line of sight of your head unit to your target could cause measurement errors - whether those are mesh, windows, glass, plastic, or something obvious like a steel beam. Just like these obvious inhibitors, water and dust are a similar barrier, but are less obvious.

With the EDM (laser) for instance, the tool may not be able to get a consistent read on measuring locations because the reflection light back from the laser gets distorted from hitting so much water in the air.

Likewise, for prism tracking, water or dust particles in the air may have a similar affect - the tool may struggle to find or lock on to the center of a target. Sometimes you may see messages such as "measurement failed" or, you may notice that the tool's live measurement calculations seem to be "jumping" even though your prism is perfectly still. This is likely from the tool struggling to find the center of your prism's location. It could also be from vibrations or wind.

In fact, even the telescope on the head unit, if it has not acclimated fully to the weather yet, may appear foggy on the inside. Even this small amount of fog will inhibit measurements and you might get a "mirrors blocked" error.

All of these factors may contribute to layout frustrations: measurement errors, longer time for the total station to calculate distances, calibration errors, etc.

Lastly, the camera of the head unit as well, that you observe on your tablet, will struggle to see images clearly. This means that it will be hard to accurately dial in manually on the cross hairs of certain targets you are using.

What is recommended when working in wet or dusty conditions?

If your layout requires extremely high tolerances, perhaps consider only performing your layout when the conditions have improved.

However, the tool is rated to be able to work in the rain. To help you in these conditions, consider protecting the head unit with a covering like an umbrella - this will help the tool perform calibrations accurately during your work and help keep its calibration mirrors clean. Also, carry a towel with you as you layout, drying the prism you are using with your prism rod, helping the tool can accurately connect to the center of it.

How should I store the PLT 400 after working in rain, snow, or dusty conditions?

While the tool is rated to work in rain, snow, and dust at an IP rating of IP55, never store a tool while it is still wet – the tool and the inside of the case needs to be dried prior to storing.

Storing the tool in wet conditions will create a humid environment to fester around the tool, subsequently causing moisture to naturally gather within the tool itself. This internal moisture will then fog the lens inside the tool, making it impossible to remove manually. Moisture inside the tool will only be able to naturally dry out as the tool sits for a period of time in dry conditions, acclimating to the environment. The time it takes to dry water from the internal lese of the tool could take even up to 24 hours.

How do I ensure the tool is properly dry?

In sum, it is important to simply use a cloth to inspect the entire tool (and inside of its case) and dry any visible water spots. This is especially important, however, on the lens (1), the collimator (2), and the two calibration mirrors (3). These locations run your calibrations and measurements as the tool is being used, and if water is inhibiting them, it could lead to calibration and measurement failures.