EKO INSTRUMENTS CO., LTD. VIP Checker HC-121 Instruction Manual V2
Pg. 16
As shown on Figure 6-13b for a measurement in wide range of thermal conductivity, exponential
approximation can be used if the relationship of value between the thermal conductivity log and output log
become almost straight.
2. Preparing Reference VIPs
Prepare 3 types of VIP which have different thermal conductivities.
When exponential approximation is selected and for example preparing three thermal conductivities of
1.3mW/mK, 5.3mW/mK, and 23.2mW/mK, the measurement results are plotted on almost straight line in
equal distances on double logarithm charge as shown on Figure 6-13b. If a measured plot is off from this
straight line, either the measurement was unsuccessful or this method is not appropriate for this VIP. As you
can see from above graph, VIP with far apart value can be accepted; however good calibration curve cannot
be drawn when the thermal conductivity values are almost the same even if there are three VIPs
When VIP sample with wide range cannot be prepared, it is possible to measure very narrow range by
selecting the linear approximation. In such case, there are some values goes off the calibration curve, so
repeat the measurement again.
There are cases that calibrated samples vary by time, so following procedures are recommended:
Perform calibration once per week at initial stage.
Once confirm that there are no variation seen on the calibration result, perform the calibration once
per month.
Also correlation of Sensor Unit outputs are lost if the VIP material and thicknesses vary, so
make sure to
perform calibration using the same material, same size as the VIP which is evaluated.
Although the output higher than near-value but lower than reference value is indicated as nNG, and
determined as Not Good , it is recommended to repeat the measurement. Less than near-value is
indicated as NG and processed as Not Good .
Figure 6-13b. Calibration Curve by Exponential Approximation
When plotting the
relationship between
thermal conductivity
and output on the
double
logarithmic
chart, in many cases
the plots lie on a
straight line. In such
case, calibration curve
can be calculated by
exponential
approximation
