The BM25 is a compact, automated high voltage, battery powered instrument used to carry out Polarization Index, Step Voltage, and Dielectric Discharge tests as well as spot Insulation tests. The BM25 has a resistance measurement capability up to 5 TΩ and leakage current measurement enables resistances up to 500 TΩ to
be measured.
The design of the instrument takes full advantage of microprocessor technology and features a large, clear liquid crystal display, combining digital and analogue readings of insulation resistance.
Set nominal voltage options of 500 V, 1000 V, 2500 V and 5000 V are selectable. A variable output voltage setting provides a range of 25 V to 5000 V incremental in 25 V steps.
At switch on, the instrument carries out a calibration self check which automatically adjusts the measurement system. The calibration sequence inhibits any testing if the measurement system fails to meet preset limits.
On starting a test, the HV warning LED on the front of the instrument flashes, together with the display HV warning symbols.
The integral timer starts automatically and displays minutes and seconds elapsed since the start of the test. The timer can be used to set the duration of a test, and will automatically stop the output voltage when the set time has expired.
During a test, measurements are automatically sent every 5 seconds via an isolated optical link to the RS 232 connector to enable downloading of the results to a computer.
Battery capacity is continuously displayed by a segmented indicator. The indicator flashes when the battery requires recharging. Power is obtained from two parallel connected sealed rechargeable lead acid batteries. If either battery fails (or an internal protection fuse ruptures) the instrument will continue to operate on
the alternative battery. The battery is recharged by external 95 - 265V a.c., 50-60 Hz, or 12 V d.c.supply.
Charging connections, mains power indicator and instrument protection fuses are located in a splashproof protected recess in the front panel.Specially designed lid hinges enable the lid to be removed and replaced as required, and will protect the lid from strain or damage by unclipping itself if unintentionally opened past its full extent.
Design safety features include:-
• The flashing HV warning LED on the front of the instrument ,and the flashing H.V. symbols on the display remind the user that hazardous voltage is present when testing.
• External voltage >50 V displayed with flashing H.V. symbols on
the display.
• Load automatically discharged at the end of a test, and decaying voltage (> 50 V) displayed.
• Interlocked sliding cover to prevent simultaneous access of charging and test terminals.
• Test terminal sockets lock test leads into the case and prevent accidental disconnection.
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