Test Equipment in 30C Heat?

[MosFett]

I'm wondering about keeping some test equipment (o-scope, function generator, DMM, LCR meter, PSU) in a garage that gets to be about 30C regularly. I believe the max operating temperature for such equipment is usually around 40-45C (this is what I remember seeing in user manuals), so it seems it should be fine, but I wonder if the calibration will drift noticeably faster in the warmer and more humid semi-outdoor environment. Do you know how sensitive test equipment generally is to heat and humidity?

[TimNJ]

Well, oscilloscopes generally aren't "precision" instruments per say, with 3-5% vertical accuracy, typically. Even if there was some effect on accuracy due to temperature, it probably won't have much effect on your ability to diagnose/debug circuits.

But even for your other instruments, I think the references they used are usually qualified across a pretty wide operating range. Even $50 multimeters with SoC multimeter ASICs typically have bandgap references with 75ppm/C drift or less. With 20 degree C shift, you might be off by 0.1-0.2% or so, including other drifts, particularly gain of the ADC(s). In that case, you'll probably still be well within the spec of your $50 multimeter. If the ambient temperature falls within the operating temperature range of your equipment, then it should meet all of the specs on the datasheet.

Similarly, if you have a $1K+ bench multimeter, it will likely have a much more stable reference, <1ppm/C or so, and many times are temperature compensated (via a heater). In this case, these meters should still meet their specs even with elevated operating temperatures. Their references and amplifiers should be equally better to allow solid performance across wide operating range.

Long term though, I'm not too sure. I know references experience time-related drift, related to physically how long the references have been powered up, but I'm not sure if being exposed to elevated temperatures can have a similar effect.

[DaJMasta]

When test equipment is specified to run in a wide range of temperature environments, it is specified to meet its lifetime and accuracy specifications in that window.  Yes, you will see more drift in your references and yes, you will probably slightly reduce its overall lifetime, but it will be within the design specifications of the instrument provided it's been well engineered/tested and not faulty.

Odds are good that you'll be able to measure the effects on drift, maybe even with the instrument being used, but it should be within stated specifications if you're within the temperature range.  If you end up losing power in the middle of a hot day and the garage spikes up another 10C, maybe you'll run into some issues there.

[JohnnyMalaria]

My lab is an air-conditioned garage in North Carolina. I keep it at 25C because of the nature of the things I test (liquids) and have to measure phase differences of a fraction of a degree with high precision. My equipment is a combination of off-the-shelf precision electronics, not so precision and homebrew plus a bunch of optics. Many labs in academia and industry operate at 25C. A short while back, my AC crapped out and the temperature in the garage got up to 32C during the day for a few days. My instrument was fine and is chugging along. The opposite happened this past winter when the temperature in the garage didn't get above 10C for a week. That screwed things up only because I couldn't generate data at an appropriate temperature to allow comparison with those in the scientific literature.

[MosFett]

Thanks for the info. I'll sleep better knowing I'm not cooking the life out of my equipment 

[Kleinstein]

The temperature will usually not have a very large direct effect on the accuracy. The high accuracy voltage refs. (LTZ1000, LM399) use temperature regulation and thus are at the same temperature anyway. The temperature effect on the reading is also mainly temporary.

However things like the power-supply and other circuit part still usually see a higher temperature and do age a little faster in hot environment. However Failure due to normal aging is only one way for instrument to fail - over-voltage and similar mishaps are another way and this is not temperature related. It kind of makes sense to keep ventilation slots open and  give the fans space to work with.
A 10 C higher temperature might accelerate aging by a factor of 2 - so usually not a problem if just for a few hot weeks, but it could be a factor if all the time.

Precision instrument are often made for rack mount and it can get quite hot in there, even if the lab has AC at 25 C.  So many of those instruments are made to also work at 30-40 C. There is also an effect of altitude on how well cooling works - at 1000 m altitude cooling might get 10 % less effective and is thus more critical.

It also depends on the Instruments. Especially older RF parts ran rather hot and do not like the higher temperatures. A DMM is usually less critical.