Chauvin Arnoux C.A 6549 Mode D'emploi page 74

CALCULATION OF ∆ ∆ ∆ ∆ ∆ T FROM STORED DATA
4.5.3
The coefficient ∆T is used to calculate the insulation resistance at a temperature other than the
measurement temperature (cf. § 4.3).
It is the temperature difference at which the insulation concerned is divided by 2.
This coefficient is variable: it depends on the type of insulation.
When it is not known, the instrument can calculate it from three or more stored measurements.
Attention, these 3 measurements must have been made on the same device (identical insulation) but at 3
different temperatures, and the temperatures must have been recorded (2nd function + T°) at the same time
as the measurements, without applying the correction (Resistance Correction OFF).
Procedure :
In SET-UP, select Calculate ∆ ∆ ∆ ∆ ∆ T from Memory
§
and press 4
The display unit proposes all values recorded with
a temperature
§
Select at least 3 measurements using the
4,3,5 and 6keys.
∆T is calculated and recorded automatically
§
once 3 stored measurements have been
selected, and updated as more measurements
are selected.
§
The larger the number of measurements, the
more "accurate" the calculation of ∆T.
Note : this calculation is possible only for resistance
values < 200GΩ.
4.5.4 MAXIMUM OUTPUT VOLTAGE
§
In the SET-UP menu, select Maximum Output
Voltage
§
Adjust the maximum output voltage using
the4key, then the 5 and 6keys.
This function prohibits the use of certain test voltages for the insulation measurement.
The instrument can then be used by less experienced persons for specific applications (telephony,
aeronautics, etc.) where it is important not to exceed some maximum test voltage.
For example, if the maximum output voltage is set to 750V, the measurement will be made at 500V in
switch position 500V, and at not more than 750V in all other positions.
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