8
2.1. fUNCtIoNS
C.A 6550 and C.A 6555 megohmmeters are high-end portable measuring instruments intended for the measurement of very high
electrical insulation and resistance values, mounted in a rugged site housing with a cover; they have graphic screens and can
operating on battery or mains power.
The C.A. 6550 makes insulation measurements at voltages up to 10,000V, the C.A. 6555 up to 15,000V.
Their main functions are:
detection and measurement of input voltage, frequency, and current;
quantitative and qualitative insulation measurement:
measurement at a fixed test voltage of 500, 1,000, 2,500, 5,000, 10,000 or 15,000V
dc
;
measurement at an adjustable test voltage between 40 and 15,000V
dc
;
measurement with a voltage ramp from 40 to 1,100V, or from 500 to 15,000V;
measurement with a voltage in steps from 40 to 15,000V;
non-destructive (Early break) test, test stopped at a preset current (Break at I-limit) or Burn-in;
calculation of the DAR, PI, and DD (dielectric discharge index) quality ratios;
calculation of the measured resistance referred to a reference temperature.
measurement of the capacitance of the circuit tested;
measurement of the residual current.
These megohmmeters contribute to the safety of electrical installations and equipment.
Their operation is managed by microprocessors that acquire, process, display, and store the measurements.
They have many advantages, such as:
digital filtering of insulation measurements;
measurement of the voltage;
the programming of thresholds to trigger audible alarms;
the timer for measurement duration checks;
the programming of a limitation of the measurement current;
the plotting of the voltage and resistance curves;
protection of the device by fuse, with detection of defective fuse;
operator safety thanks to the automatic discharging of the test voltage on the tested device at the end of the measurement;
automatic power save mode of the device to save battery power;
indication of battery charge condition;
large graphic display with backlight capability;
a memory to store the measurements, a real-time clock, and a USB interface;
data export to a PC (using the software provided).
2.2. dISPLAy
The display unit is a graphic display with a resolution of 320x240 pixels.
It has built-in back-lighting, which can be controlled by a long press on the
key (see §1.4).
2.2.1. ExAMPLE of dISPLAy bEforE tHE MEASUrEMENt
FIXED VOLTAGE
1000 V
Input voltage
Frequency
Input current
Date 2011.05.23
-0.1 V DC
0.2 Hz
112 pA
Time 10:31
BURN
500 V
2500 V
ALARM
Test Run Time 00:02:00
The blinking value can be
modified using the
keys.
Condition of the batteries.
Test with programmed duration.
The alarm is active.
Programmed duration of the test.
Value of the external voltage
present on the terminals and its
frequency.
Current flowing between the
terminals.
Date and time.
Value of the next lower available
test voltage.
Value of the next higher available
test voltage.
Type of test voltage.
N o c u r r e n t l i m i t a t i o n
programmed.
