Calibrating weighing machines
If you buy a balance (scale) for over £15.00 we check it before dispatch. We check that it powers up, then we check that it is weighing correctly, and if it's not weighing correctly we calibrate it. For a balance (scale) costing less than £15.00 we merely check that it powers up (see How often should a balance need calibrating below).
Another article: everything you need to know about weighing and weighing machines.
Every balance will go out of calibration given enough time, or if bumped or dropped. The readings become inaccurate. It is possible that it will be 'broken' but it is much more likely that it merely needs calibrating.
Or you could look at it this way: one day your balance will "break down", but the chances are that you can fix it simply by pressing buttons as you place weight on the weighing platform.
Some balances are supplied with calibration weights, some are not (see each item description) so you might need to buy a weight.
You will also need the instruction leaflet that came with the balance (the calibration instructions vary from model to model).
IF THE BALANCE IS NEW IT WILL STILL BE FACTORY-CALIBRATED, LEAVE IT ALONE!
IF IT IS READING CORRECTLY, LEAVE IT ALONE!
IF IT AINT BROKE, DON'T FIX IT!
WHAT IS 'CALIBRATION'?
The reading on a measuring device (any measuring device, e.g. a thermometer, weighing machine, clock...anything) must match the units it is measuring (e.g. degrees, grams, minutes). This matching-up is called calibration. Electronic machines go out of calibration, it is the nature of electronics.
When a balance goes out of calibration the readings will not match the units, e.g. a 100g weight might weigh 105g.
Every scale will go out of calibration given enough time. In the scientific industry scales have the calibration checked every year. That is why every scale in a laboratory or hospital has a sticky tab with the date it was last checked. A technician will call, he will check all the scales in the building, he will calibrate any that are not accurate, he will charge about £150.00 for the visit. If you have a low-value scale it is cheaper to calibrate it yourself. Buy a weight and follow the instructions in the instruction leaflet. When a balance become inaccurate and needs calibrating, this is not a fault!
HOW DO YOU KNOW IF IT NEEDS CALIBRATING?
Weigh a weight, if it is reading correctly, the scale if fine, there is no need to calibrate it, just leave it alone.
If the balance is not reading correctly, it will probably need calibrating.
If the display is slowly 'drifting' up and down, even when nothing is being weighed, this means that someone has seriously overloaded the balance, it is beyond repair. You will see an error code. These vary from make to make, some common error codes: EEE, 0-Ld and OUEr. If you see any of these, your balance has had a serious accident and is beyond repair.
Calibrating it yourself involves pressing buttons (sometimes in a complicated sequence) and placing a weight on the weighing platform.
Which buttons do you press?
It varies from model to model. See the instruction manual.
Which weight will you need?
It's usually the maximum weight the scale will read (e.g. 500g for a scale with a capacity of 500g). Some scales require two weights. Annoyingly, most of the instruction manuals don't tell you which weight you need, they just say, "place the required weight on the weighing platform". The good news is: we do tell you which weight is required, see the item description.
Do not try to calibrate a balance without the weight, you will merely reprogram its electronics and then won't be able to use it until you buy a weight and calibrated it properly.
HOW OFTEN SHOULD A BALANCE NEED CALIBRATING?
How often you have to calibrate a balance depends on the quality of the balance.
Very approximately, this is how often you should calibrate it, and this applies to any scale bought from anyone, irrespective of what the seller claims!
- if you paid a few hundred pounds, every year or two
- if you paid about £100.00, after about a year
- if you paid about £50.00, every few months
- if you paid about £20.00, every few weeks
- if you paid about £15.00, every few days
- if you paid about £10.00 it might be a good idea to calibrate it every time you turn it on, this is not a fault, you get what you pay for.
Some of the 0.001g scales need calibrating every time you switch them on, they are supplied with the calibration weights. Of the other scales, some come with calibration weights, some do not (they are an optional extra), see each item description.
There is no harm in calibrating your scale every few months, weeks or days, but it is not necessary unless it has become inaccurate. It is more important to check it regularly (by weighing a weight) to see if it needs calibrating.
SPECIAL RULES FOR APPROVED BALANCES
Approved balances are for use in trade (buying by weight). We sell Ohaus, they have a special calibration system: you pull a lever which lowers an actual weight onto a duplicate weighing platform inside the scale. This is to stop the user using an inaccurate weight and ending up with inaccurate readings. This 'pulling a lever' method is somewhat low-tech - but that is why these scales are relatively low-cost.
We usually have some that are secondhand and clearance.