What should always be on+

[FriedMule]

I know that a unit often perform better if it has been turned on for a while but what is it that have to be kept on?
A standard handheld multimeter can be turned on and used within seconds and perform.

Let's say you have a frequency counter with external (always on) frequency reference, is it then necessary to keep the counter on all the time?
What about your bench DMM, our scope, the power supply, electronic load and so on?

I am asking because electricity is expensive and I do want to keep the necessary gear on but not the gear where the difference is minimal. A UNI-T UT801 2000 count will be bad no matter if you keep it on or not. :-)

[Jwillis]

Some very high precision equipment may require temperature stabilization to perform it's function accurately but that type of accuracy probably won't be found it a hobby lab or repair shop. 
Most electronic equipment does not need to be on or require power when inactive unless it has a remote control , volatile memory  , capacitive  or soft touch switches for power on . But if your not concerned about the convenience of remotes or fancy touch switches these can be turned off completely as well with out any problems.
Volatile memory requires a small amount of power to maintain what ever information it may contain like settings or logged data  . But I'm not aware of any  equipment that uses this type of memory aside from calculators . Most equipment uses non-volatile memory which does not require power to maintain data.
 I don't have test equipment that has memory functions other than a soldering station but it holds settings even unplugged . Maybe some one may know of test equipment that does use volatile memory to save settings .
 

[harerod]

Why not check in with the voltnuts in the Metrology section?
Those guys really go out of their way to keep some units under power, e.g. their LTZ1000 references.


For standard use one might want to consider mechanical stress due to temperature cycles. Just keep the unit powered, even if you are using it only once every half hour.


Regarding stabilization: have a look at the manual. My bench multimeter 34470A takes about 90min to stabilize fairly well, so that would be a hint for which expected idle times to switch off.


Additional hint: many manufacturers define reliability by both MTBF and power cycles. (hard drives, light bulbs, ...)

[FriedMule]

As I understand both your answers is it beyond my need in precision to keep a unit on 24/7 but maybe should I keep my trusted Bench DMM on 24/7.
For the rest can I just switch off on the outlet.

If I maybe use a unit once or twice that day, do I keep it on until I leave the lab, but I find no reason for powering on an old scope, power supply or something I will not use at all that day.

Do any of you have gear you never turn off, just like a frequency standard?

[rsjsouza]

I tend to power off anything I am not using, but one remark regarding volatile RAM: some of the older equipment uses a non-rechargeable battery to keep the contents of static RAM - my Racal Dana 5001 uses a CR123 to keep its calibration constants.

[Jwillis]

I tend to power off anything I am not using, but one remark regarding volatile RAM: some of the older equipment uses a non-rechargeable battery to keep the contents of static RAM - my Racal Dana 5001 uses a CR123 to keep its calibration constants.

Oh Right . I forgot about those batteries. I have had to remove such batteries to reset to factory settings on some other equipment. Thanks for reminding me .

[ElizatronicWarfare]

Voltnut here - check the manual for the equipment you are using. Any precison equipment that requires a warm-up period like benchtop multimeters or frequency counters will have that warm-up specified somewhere in the manual (usually in the measurement procedure or next to the specifications). Most handheld or battery-driven equipment has no such warmup time, and short-term aging effects are accounted for in the design and/or specifications.

[Gyro]

I would think twice about leaving anything with a VFD on permanently - unless it has a display blank function.

[voltsandjolts]

If you are unsure whether you should have it constantly powered, then think of the environment and default to unpowered.

Only when there is a very good technical reason for it (which you need to fully understand) should you leave it powered.
This will depend upon the equipment in question and your measuremement requirements, neither of which are clear in the OP.