Frequently Asked Questions
Calibration
As a manufacturer of inspection equipment Elcometer provide calibration certificates for all applicable gauges.
On the certificate we state both a Calibration Date and an Issue Date.
The Calibration Date is when the gauge is calibrated at the end of the production process and the Issue Date is the date of invoice when the gauge is taken from stock and sent to the user.
With the gauge stored correctly and unused the gauge will remain in the same condition as it was calibrated at the end of the production process.
It is only through use that the gauge calibration may change.
Therefore, an End User should use the Issue Date as the valid start date for the duration of the Calibration Certificate.
The next calibration date is determined by the Quality Procedures of the user and can range up to 3 years depending on the frequency of use of the gauge.
Typically, many Quality Procedures will require a recalibration of the gauge after 12 months use.
Most Elcometer gauges are supplied with test materials (CTG – Foils, Gloss have calibration tiles etc) that will allow the user to verify the accuracy of their gauge on a daily basis and should the gauge not measure accurately it can be returned for servicing and recalibration independently of the scheduled recalibration date as determined by the Calibration Certificate.
Certificates are issued in accordance with ‘ISO 17025 Clause 7.8.2 Common requirements for reports’
There are 16 requirements, the one’s causing most of the questions are:
i)The date(s) of performance of laboratory activity; (date of calibration)
j) The date of issue of the report;
Coating thickness gauges cannot be issued with Calibration certificates due to them being variable calibration units. You can only issue a calibration certificate if the instrument or gauge has fixed calibration.
Elcometer offer test certificates for the gauges and probes to show compliance to our specification.
To assist the customer we offer calibration certificates for the foils as they comply to the fixed calibration requirements. The certificate issued with the foils shows traceability of our equipment to UKAS. All equipment used for foil calibration are calibrated at a 3rd party UKAS Calibration Laboratory.
If the gauge measures the certified foils accurately then the gauge is working correctly and within specification. If the gauge cannot be adjusted to measure the foils correctly then it should be returned to Elcometer for re-certification.
With reference to your question regarding calibration of the Elcometer 138 Bresle kit. The conductivity meter supplied does not require returning for calibration, it is set up using the solutions supplied, one is a specified test solution which is supplied by the meter manufacturer to set the gauge before use. The second deionised water which cleans the sensor before and after use.
Please be aware that due to the methods employed to calibrate F510’s and requests from customers.
“All the 510s are calibrated on 20mm load cell, to convert that to 50mm they just multiply by a factor of 6.4 to amend the surface area increase as the pull is linear.”
When the customer orders a set of foils there are nominal sizes given which we identify on the calibration certificate to ensure the customer receives the correct values. The nominal values have a purchasing specification of +/-10%.
We then measure them using our Solartron Linear Encoder and calibrated gauge blocks, we then issue the measured value along side the nominal. The foils supplied are accurate to within +/-1% or +/-0.5um whichever is the greater of the STATED MEASURED VALUES. The nominal value is just to confirm the correct foils, this value is not the specification.
Elcometer advise customers that they should have their equipment re-calibrated every 12 months under normal usage. However, if the customer uses the equipment on occasion they can extend the re-certification period up to a maximum of 3 years. Evidence must be retained of the calibrations to show equipment is still within specification.
Foils carry the same recommendation but due to the nature of the material’s used and thicknesses, you must replace any foil, which is creased, or showing holes or serious indents. This mainly applies to the thinner foil values.
We generally recommend the customer have a calibrated set in the office or calibration lab to use for checking the equipment on a monthly basis (under normal usage) and a working set on the factory floor which can have the various foils replaced as they wear out.
Regarding your question, the Zero point is a piece of specific steel and aluminium, we serialise them and replace them after approx. 400K/250K readings as they mark. There is no actual calibration as it is a zero point, hope this answers your question.
With reference to your question regarding UKAS traceability (ISO 17025). Elcometer are not UKAS approved but the equipment we use for Calibration and Testing is. The gauges we supply have no ‘British’ or ‘International’ standards that they have to comply with, they are used in accordance with various Test standards. We define the specification and accuracy.
Coating Inspection
The instruments contain trace amounts of particular metals such as Tin which is the main constituent of solder paste.
The Printed circuit boards contain solder, which is protected by a flash coating of Gold, this is sub-micron thickness which mainly burns off in the solder process but some will remain in the solder.
There are some Tantalum capacitors within our circuit but again it is a very small percentage by weight of the overall unit.
The 456 separate instruments can be used with various probes and is used for displaying readings; data collection, data manipulation and setting of the probe to relevant thickness as such can only be issued with a certificate of accuracy.
Separate probes are issued with a test certificate showing readings taken on calibrated foils. The probe once plugged into the instrument should be calibrated on a foil close to the value of the coating thickness to be measured.
General Questions
The 2 marks are the start and finish point for the wire eroding machine. They are present on all the combs produced. It is not a fault, but a witness mark caused during the machining process they have no effect on the combs function.
Equipment Used:
Jenway 4510 Bench Conductivity meter & Probe
High Purity Water
Syringe
Needle
Beaker
Process:
Every new production batch of Bresle patches are measured for the surface area and contamination levels.
We measure general contamination not specific contaminants. The test is carried out in the test room at a temperature of 25°C as per the specification.
We use samples from the batch run, first offs, middle section and last offs to ensure consistency throughout the run.
Every batch test uses a new bottle of high purity water, syringe and needle. The test probe, needle and beaker are cleaned using the high purity water prior to any testing.
The test probe is placed in the beaker containing the high purity water to check the contamination level of the water. This is subtracted from the final result to give the actual contamination level of the patches.
Samples are created using 2 patches, the central core peeled out and the 2 patches stuck together to produce a sample we do this several times. We then place 3ml of pure water per patch into the scaled syringe to ensure the correct amount is injected into the samples, this equates to 6ml of water per sample under test. The water is moved around the sample by pressing on the outside to ensure all parts of the test area are covered.
The water is removed using the syringe and needle from the samples under test and poured into the clean beaker and the sample is tested using the Conductivity meter. This shows the temperature and the contamination level in uS/cm, the original water result is subtracted from the test sample result, at which point we have a correction factor (x1.2) to convert into mg/m² which is the actual contamination level.
All 106 instruments have a zero-set point, but this is placed in brackets as it is just a ref point for engraving detail.
The instruments cannot be set to zero due to the basic measurement process, the design of the springs or spring washer’s dependant on scale all instruments are set up on the first defined scale reading, this then sets the height of the barrel with the aid of spacers. This may show the ref zero slightly above or below the measurement line (edge of the main body).
Once the initial pressure is set at the first defined scale point all further measurements are taken to ensure the unit meets its technical specification.
For general information the uncertainty values for foils are,
Up to and including 1.5mm uncertainty is +/-1um
Above 1.5mm up to and including 4.0mm uncertainty +/-2um
Above 4.0mm uncertainty +/-4um
Surface Preparation
When the customer orders a set of Verification tiles there are nominal sizes given which we identify on the calibration certificate to ensure the customer receives the correct values.
They are then measure using our Digital multimeter, we then issue the measured value alongside the nominal. The Verification tiles are accurate to within +/-0.15% of the reading of the STATED MEASURED VALUES. The nominal value is just a guide, this value is not the specification.
Adhesion & Surface Testing
The ASTM tape’s we supply are issued with an expiry date. This date is applied by the manufacturer and should not be exceeded as the adhesive properties will deteriorate.
With reference to your question regarding the bubbles in the adhesive tape, this is called fisheye by the manufacturers and is not uncommon. They advise the tape is suitable for use, once applied the little pockets should disperse and function as the tape should.
As noted, the manufacturer of the tape moved production from their Swiss plant to their plant in Italy but maintained the same production process and materials.