Lab equipment questions

Question

I have an OWAN XDM2041 bench multimeter on order. Studying the online owner’s manual It says it takes 30 minutes to warm up. This raises two questions. First, why so long to warm up? Second, because I use it randomly throughout the day, do you think it harmful to leave it powered on all day? Nobody wants to wait 30 minutes to take a measurement. Thank you for your consideration of this issue.

baldengineer · Accepted Answer

A new thread is usually preferred for each unrelated question. It makes it easier to focus the answers on it. (Also it helps for indexing and searching when someone else looks for the same information.) In general, yes the mains plug is sufficient for safety. According to your multimeter's manual (Page 3, LO terminal), the terminals float above earth ground with 500V of isolation. So the chassis screw is just for the chassis. The only time I can think to use that is if you're measuring a floating DUT and you want to give it a path to earth ground. Here is a good reference for grounding: https://www.keysight.com/us/en/assets/7018-01897/technical-overviews/5989-9200.pdf

fmilburn · Answer

Hello William, The warm up time refers to the time required to achieve the full accuracy and precision in the datasheet since the components have some variation with temperature and this is true of all meters. The multimeter like most electronics can be left on for hours at a time without issue. Try taking measurements with the instrument cold and then after it has warmed up. For common uses the differences in a warm and cold reading don’t matter.

baldengineer · Answer

billinrosehill wrote:
Nobody wants to wait 30 minutes to take a measurement.

And almost nobody does. The warm-up time is the time required to ensure the calibration is valid. Which does not mean the measurements are useless or wildly inaccurate. Sure, the measurements could be slightly off, but not enough it would matter in most cases. How you probe your circuit vastly affects the accuracy of the measurement more compared to the warm-up state of the DMM.

The more important reason to for the warm-up period is because the measurements are not traceable until the temperature is stabilized. In other words, if you were going through a test plan for a device then you would wait for all the equipment to warm up. If you're debugging something or making a quick measurement (how DMMs are used 99% of the time), then there is no reason to wait.

Jan Cumps · Answer

The DMM6500 specifies a wait time of 30 minutes for adjustment, calibration and high precicion measurements.

An additional 30 minutes if it has been +-10 ° outside the operating range.

They do not specify a warm up time for generic use.

billinrosehill · Answer

Hi Frank. Thanks for the information and the tip. I look forward to trying the warm / cold comparison.

Jan Cumps · Answer

The XDM2041 is a rather advanced device. For learning, a simple and cheaper DMM would make the learning curve less steep.

Lab equipment questions

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