jccantrell Nov 23, 2014:

My two cents I would say that these terms can be interchanged ONLY if the device is operated 24/7 around the clock. Then, if the device must be calibrated every two years, then that would correspond to two years of constant operation. Usually, though, in my experience, calibration is used to make sure the device is giving you correct data. So, if it is a thermostat used to switch on heating for something, it must be calibrated to make sure the heating comes on at the right temperature. If the machine is switched off every two months for a week of maintenance, then the calibration interval is not the operation interval. So, I would check with the customer to make sure that they do not want to edit the source text too so as to avoid confusion. Editing the source would eliminate your dilemma also.

Terry Richards Nov 22, 2014:

@Tony I had to read that a couple of times before I got your point. One of the disadvantages of working on a Saturday morning!

Yes, if you are talking about the calibration operation rather than the operation of the device itself then 'operation interval' can be correct, particularly if there are a lot of 'operation intervals' in the document.

However, it's potentially confusing and I still wouldn't recommend it even though I do now concede that it is not necessarily wrong in an absolute sense.

Tony M Nov 22, 2014:

Right! Well, you see, Terry, not necessarily!

The overal section is cleaarly referring to calibration operations; as such, it is perfectly valid to say that, for this particular operation of calibration, the operation interval is....

I don't think it's good writing, but it's understandable and not actually wrong. It might be appropriate, for example, if there were other different operations to be carried out, and each of these had a sub-heading 'Operation interval'.

Mitsuko Yoshida (asker) Nov 22, 2014:

Operation interval
It must be calibrated once every two years.

is the paragraph. Thank you for your help!!

Terry Richards Nov 22, 2014:

As operation and calibration are completely different things, the only time it would be correct to use 'operation' instead of 'calibration' would be if 'calibration' was wrong in the first place.

As you have provided no useful context, we can't tell that.

Landsknecht Nov 22, 2014:

Calibration and operation are different things: the former is a precondition of the latter.

Tony M Nov 22, 2014:

@ Asker Entirely depends on exact context!

Please give the whole sentence, or even paargraph, in which the term is used.

At first sight, I'd say no, it isn't OK — but it does entirely depend on exactly how and where the term is being used.