Trimble GX scanner in the cold

I would hazard a guess it has to do with the critical tolerances inside the scanner and the change in thermal expansion/contraction based on the temperatures.

Not for the Trimble but here is a link for a jacket developed for the Leica. It didn't say why a scanner will not function below a certain temp but it seems that the Leica has the same restrictions.

Warm Jacket

LCD display? Those usually don't like to work in severe cold.

Also some semiconductor technologies get slow at cold temperatures and miss the internal timing allowances so that they don't function correctly.

I'm not sure of the reason(s) for the limitations but I talked with our Leica representative (the Leica limitations are similar) before we purchased the ScanStation 2 for our last project. He is from Minnesota and he said that he got around the working limitation by not keeping it outside for extended periods.

He would bring the instrument out of his vehicle only when he was ready to perform a scan and then put it back in the vehicle as soon as the scan completed.

Using this method, we were able to collect scans in single digit (fahrenheit) temps. Each of our scans were generally in the 30 to 45 minute range.

I never noticed any difference in the quality of the scans in cold weather vs. warm weather.

Thanks, Deral. I am going to give a heating pad a try later today. We have some bridges to scan and it probably can't wait until the weather warms up.

We also have 50 stream sections to do, that's always fun in the winter!

we thought about that, keeping it warm in the vehicle until needed. It does generate heat internally, there is a cooling fan that cools it normally. I don't think it would be a good idea to block that.

BTW-no display at all on the GX scanner. The laptop would be connected to it and that could be in the truck if we can get within 100' of it.

There was no display on the ScanStation 2 either. We used a Dell laptop. Are you using a cable or wireless? Our Leica representative tried to get us to install the wireless connection (he said that it was a easy as setting up one for a personal computer) but we used the ethernet cable for the entire project. I think we were limited to 150' but never used more than a 100' cable.

At one time we used the wireless, but found the wired much easier to deal with. I am going to make a 150' cable for this project. usually we are right beside the scanner, but this time the scanner will have to be down along the stream bank to get underneath the bridge.

The behavior of the laser beam at various temperature ranges is a critical consideration. At the moment, I am unable to recall exactly how the trimble measures distance. It is not difficult to see that if the laser beam is traveling through really cold air the time for the return will be greater than what the nice an toasty electonics are counting internally.

The GX scanner, similar to any EDM, uses the (user input) temperature and pressure to compute a correction to the velocity of light. So, it is NOT adversely affected by temperature in that sense.

Yes, I know that,(device capable of atomsphereic corection input) but I thought the discussion was about extreme operation conditions.

An answer from Trimble and a test with heating pads

I was pleasantly surprised that someone from Trimble saw this and passed it along to the hardware team in France. Their answer was basically that "it is a high precision instrument with a lot of sensitive components. Expansion and contraction of materials due to temperature change is therefore an issue".

They sent along a tech note (that I hadn't seen before) that makes recommendations for setting up. Whereas one poster suggested keeping it warm in the vehicle and then taking it out to scan for short periods, that is NOT recommended. It is better to have it sitting in the truck cold and then take it out in the cold to scan. Similarly, one should not take it from a cold truck into a warm building to scan without letting it acclimate. It is the temperature changes that are not good.

Anyway, I bought 2 heating pads at WalMart. They only use 50 watts each so a small generator (1 KW) still has ample power for everything (scanner, laptop, heating pads). The internal temeprature (always displayed bottom left in pointscape) started at 65°F and went up to 75°F (around 25°F outside). The scanner worked fine. So, I think the heating pads are a viable option (as the engineer from Trimble stated in his email).

An answer from Trimble and a test with heating pads

Temperature changes can often cause condensation, which is definitely not good for sensitive internal electronic components in ANY surveying instrument.

We were always taught to never use the instrument straight out of the box until it had a few minutes to acclimate to the ambient temperature, and to never put it away and seal the carrying case shut until a few minutes had passed in the different temperature..