Meaning: specimen within an approximate range. Reducing factors will


 Calibration is an important process used to maintain instrument accuracy. It is a process
of setting an instrument to get a result for a specimen within an approximate
range. Reducing factors will cause imprecise measurements is a core aspect of
instrumentation design.

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Even though the
exact series of steps may vary from product to product, the calibration process
usually involves using the instrument to test samples of different known values
called “calibrators.”  The results are used to initiate a connection
between the measurement technique used by the instrument and the known values.

Calibrations are
done by using only a few calibrators to establish the connection at specific
points within the instrument’s operating range. It might be applicable to use
many calibrators to get a calibration relationship, the time and labor
associated with preparing and testing a large number of calibrators might
outweigh the resulting level of performance.


Methods of calibration:


How well an analytical method distinguishes the
analyze from everything else in the sample.

Baseline separation






Linearity: How well a calibration
curve follows a straight line.

R2 (Square of the correlation coefficient)

Accuracy: Closeness to reality

                              Compare results
from more than one analytical technique

                       Analyze a
blank spiked with known amounts of analyte. 

Precision: Reproducibility


Limits of Detection and Quantitation:

Limit of detection (LOD) –
“the lowest content that can be measured with reasonable statistical certainty.”

 Limit of
quantitative measurement (LOQ) – “the lowest concentration of an analyze that
can be determined with acceptable precision (repeatability) and accuracy under
the stated conditions of the test.”

Need of Calibration:

There are three
principle purposes behind having instruments Calibrated.

§  To guarantee readings from
an instrument are predictable with different estimations.

§  To decide the exactness of
the instrument readings.

§  To set up the
dependability of the instrument i.e. that it can be trusted.

Example: Calibration of thermometer

Calibrating your
thermometer is snappy and simple. Numerous simple and advanced thermometers
enable you to balance the temperature to change for the aligned esteem. In any
case, if your thermometer doesn’t offer a counterbalance work, a bit of blue
tape with the delta will work fine.

Technique 1: Ice

Fill a glass
with ice solid shapes, at that point finish off with frosty water. Blend the
water and let sit for 3 minutes. Blend once more, at that point embed your
thermometer into the glass, trying not to touch the sides. The temperature
should read 32°F (0°C). Record the distinction and counterbalance your thermometer
as suitable.

Technique 2:
Boiling Water

Heat up a pot of refined water. Once the water has achieved a
boiling point, embed your thermometer, trying not to touch the sides or base of
the pot. The temperature should read 212°F (100°C). Record the distinction and
balance your thermometer as suitable.

The breaking
point of water will differ with height. This helps water boiling point calculator to locate the correct temperature
for elevation.

Types of calibration:

Ø  Manual calibration:

The procedure is complex, but
overall it involves the following: (i) depressurizing the system, and turning
the screw, if essential, to guarantee that the needle peruses zero, (ii) fully
pressurizing the system and ensuring that the needle reads maximum, within acceptable
tolerances, (iii) replacing the gauge if the error in the calibration process
is beyond tolerance, as this may indicate signs of failure such as corrosion
or material fatigue

Ø  Automatic pressure calibrator:

It is a device
that consists of a control unit housing the electronics that drive the system,
a pressure intensifier used to compress a gas such as Nitrogen, a pressure transducer used
to detect desired levels in a hydraulic accumulator and
accessories such as liquid traps and gauge fittings

Factors affect Calibration:

instrument adjustment is essential to keep potential mistake sources from
affecting the outcome. A few elements can happen during and after an alignment
that can influence its outcome.

Using the wrong
calibrator values:  It is mandatory to
follow the instructions for use during the calibration process. Without
considering the instructions and selecting the wrong calibrator values will
affect the instrument incorrectly and produce various errors over the entire
operating range.