Does balance come calibrated with a certificate of calibration? NO
Does balance come calibrated with a certificate of calibration? NO.
There is no Certificate of Calibration for any of the scales or balances we sell and the manufacturer's do not supply a calibration certificate. If someone offers this and they don't come on-site to perform the balance calibration then you are being offered a fraudulent document.
We do sell calibration weight that can be purchased with NVLAP calibration certificate at http://calibrationweight.com/
Let us explain below why there is no certificate of calibration with any of the balances or scales we sell.
Balances are influenced by changes in seasonal temperature, humidity, barometric pressure and the gravitational acceleration for the location (the position of your location related to magnetic north) which the precision weighing instrument is being used. The affects of gravity differences in latitude and elevation.
A person weighing themselves would weigh slightly more at sea level than at the top of a mountain, not enough for you to notice, but a measurable amount when you are weighing using a milligram, analytical or microbalance.
It is necessary to adjust the balance when it is being installed for the first time or if you move the balance to a different locations. It is also recommended that a balance be calibrated regularly in order to maintain the most precision. Read any instruction manual from Ohaus, Mettler, Sartorius and other balance manufacturers and in the installation of balance section you will typically read something similiar to "When the balance is first installed or when it is moved to another location, it must be calibrated to ensure accurate weighing results".
In addition, most GLP/GMP and Quality Assurance Directives for a ISO manufacturing environment require in their procedure a daily calibration. Also, in critical weighing applications such as formulation of inks, paints and adhesive a daily calibration is a must.
Here is an example of an standard operation procedure (SOP) for calibration of balances from the US EPA. You can review a calibration procedure for a 5 decimal place semi micro balance here.
Once again - There is no certificate of calibration included with any balance we sell since this can only occur at the place of installation. Every location in the world is positioned differently to "magnetic north" and therefore the acceleration of gravity is slightly different. Add to this barometric pressure affects the acceleration of gravity depending upon your location's altitude to sea level.
Therefore the only way to attain a certificate of calibration is to do it yourself with a certified calibration mass which we sell or hire someone to perform the task. You can basically copy the calibration instructions in the manual and create a QAD (Quality Assurance Directive), QAP (Quality Assurance Procedure) or SOP. You can also create your own calibration procedure from scratch like this one here. The other option would be to hire an outside calibration or scale company to come out to the location where the balance is being used and perform the calibration. You should call a local calibration or scale company to see what they will charge to come on-site to perform a calibration since prices can vary just for the calibration from $175 to well over $300.
People sometimes call us saying a competitor or catalog company offered to ship their balance with a calibration certificate if they purchase the balance from them. Companies offering balance(s) with a calibration certificate are giving false documents unless the calibration is performed on-site. Sure, companies can sell a oscilloscope or power supply with a certificate of calibration when the power supply is calibrated halfway across the country since a power supply isn't effected by the different longitude and latitude and affects of gravity. A calibration certificate will state the date, time and location where the balance was calibrated and if the balance is being used in Cambridge, MA and the calibration certificate states calibration was performed in Houston, TX just about every quality control compliance officer will immediately red tag and place the weighing device out of service.
Calibration adjustment is a very important to the accuracy of any balance. Just as a musician must have one true tone to tune his instrument, a balance needs a true weight to tune itself. Calibration adjustment corrects the deviation between the displayed value shown on the weighing instrument display and the true mass of a known value standard as indicated by the calibration certificate for the calibration weight. Here is an example of a 100 gram calibration weight with NVLAP certificate.
Calibration adjustment is achieved by applying known calibration weight. Adjustment is done by giving a base point (ZERO) and establishing what is the full capacity (SPAN) weight. Since SPAN is normally the balance's maximum capacity, the balance now has two precise extreme points: zero and full scale. The balance can now accurately calculate all amounts in between the base point (ZERO) and full capacity (SPAN.)
ISO 9000 procedures favor the calibration of balances with an external calibration weight with NVLAP certificate.
A balance with internal motorized calibration weight is a nice feature, but costly. Most balances with the internal calibration feature also allows for external calibration.
Precision Weighing Balances typically would recommend not purchasing internal calibration if it is an option for the particular model you are considering purchasing (e.g Entris 124-1S vs Entris 124i-1S). The internal calibration is a nice feature, but it is just one more toy for people to play with and break. Most balances with an internal calibration check the servo motor for the internal calibration on power-up. If the internal calibration system is not operating properly you can't even get past the power-up sequence without getting an error code. If you can't get past the power-up sequence you can't use your balance. Finally, most quality assurance procedures along with GLP/GLP and ISO specifications clearly specify external calibration adjustment only.
External calibration is vital since it is much for convenient to send out the external calibration mass for recalibration/certification verses you can not have the internal calibration mass removed from the balance and sent out for re-calibration.
Precision Weighing Balances highly recommends you consider purchasing the required optional calibration weight at the same time you place your order for your balance. It will only be a matter of time before you are calling for the calibration mass to be delivered "yesterday". The calibration mass will also enable you to perform all calibrations within your organization and eliminate in most situations the additional expense of calling a calibration service company in.
Calibration is very important but also the installation of laboratory balances contributes on how your balance performs. Learn many important issues and environmental factors to consider when selecting a location for your balance - click here
For even more technical information about balance and scale calibration review the European Association of National Metrology Institutes Guidelines on the Calibration of Non-Automatic Weighing Instruments or Mettler-Toledo a very good question and answer web page on calibration.
Below are some of our calibration videos from our Youtube Channel.