1
$\begingroup$

I am searching for an elegant way to measure small changes in the weight of a heavy object (a potted tree) over the period of one year.

However, I do not need to know the exact weight of the heavy object (which might be about 1t) neither has the measurement to be extremely precise in absolute numbers (I am ok with detecting something which is proportional to the change of weight). Further, this long-term measurement will be exposed to changes in ambient temperature and air pressure, which should minimally disturb the measurement.

Can I do better than using load cells, which are heavily influenced by temperature? Is it possible to measure relative changes down to parts per million? For example, can I detect changes of 1 gram if the object’s weight is about 1 ton?

$\endgroup$

1 Answer 1

0
$\begingroup$

Hei Ulrich

1) In theory you can do with load cells; the key is Calibration: When you are weighting your pot, if you add 1 gram, you will read the difference (high sensitivity). But if you measure the same object one year after (or just dismantle and re-assemble all) it will be off by 100's of grams.

So you must find an object (a stone?) of similar weight of your pot, that doesn't change its weight; and use it as reference to recalibrate your load cells before each measurement.

2) For a potted tree, I will say that the amount of water in the pot and in the tree is the main disturbance. Just see how many liters of water the pot swallows when you irrigate it. And trees store large (variable) amount of water also.

Best way to do the weighting in practice? Still thinking... One idea can be to measure resonance frequencies of the trunk. Another, (if the tree is on a terrace), measure resonance freq of the terrace.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.