Chauvin Arnoux C.A 6541 Manual De Instrucciones página 42

On these kinds of parts, measurement is disturbed at the beginning due to interference currents
(from capacitive charges, dielectric absorption) which eventually cancel each other out. Therefore,
in order to get an accurate measurement of the leakage current that is representative of the insulation,
it is necessary to carry out the measurement over a long period of time so as to reduce the influence
of any interference currents when measurement is commenced.
Next we calculate the ratios such as the PI or the DAR :
PI = R R
10 min /
DAR = R
1 min /
The quality of insulation depends on the results found.
Using the R-DAR-PI function
I I I I I
During or after measurement, the R-DAR-PI button allows you to scroll through the following values:
- DAR (for measurements lasting > 1 min)
- PI (for measurements lasting > 10 min)
- Capacitance in µF (only after the measurement has stopped and the circuit has been discharged)
- Insulation resistance in MΩ, GΩ or TΩ
Automatic measurement of DAR or PI:
If the R-DAR-PI button is pressed when in voltage measurement mode before proceeding with a
measurement, then the following is displayed:
- - - - MΩ
↑
Depending on the choices (DAR or PI), the measurement goes as follows:
a) DAR : press START → the DAR symbol flashes and the display indicates "- - - -" as long as the
calculation of the coefficient is not possible (t < 1 mn).
e.g. :
After 1 min, measurement stops and the main display automatically shows the DAR value.
During or after measurement, the R-DAR-PI button can be used to see the insulation measurement
carried out, but it does not give the PI value since the measurement has not lasted long enough.
b) PI : press START → the PI symbol flashes and the display shows "- - - -" as long as the calculation
of the coefficient is not possible (t < 10 mn).
e.g. :
After 10 min, measurement stops and the main display automatically shows the PI value .
During and after measurement, the R-DAR-PI button makes it possible to display the DAR (after
1 min), the PI (after 10 mn) and the insulation measurement.
(2 values to take down during a 10 min. measurement)
1 min
R (2 values to take down during a 1 min. measurement)
30 s
DAR PI State of the insulation
< 1.25 < 1 Inadequate, even
< 2
< 1.6 < 4
> 1.6 > 4
→
DAR - - - -
DAR
- - - -
PI
- - - -
42
dangerous
Good
Excellent
→
PI - - - -