Built to provide all the necessary features for electrical installation testing and servicing needs, the BMM500 series from Spescom MeasureGraph is designed to maximise the features that are of real benefit to the electrical contractor or service engineer competing for business in today’s market.
All instruments are microprocessor-controlled, combining outstanding performance with ease of use. For ultimate reliability the BMM500 series is waterproof and dustproof to IP54 and is supplied with a three-year warranty.
Intelligent Safety System (ISS)
With increased pressure of time to complete jobs it is inevitable that whilst performing tests on an electrical system, mistakes will occasionally be made, exposing the user to danger or under certain circumstances damaging the instrument. The BMM500 series incorporates Megger's Intelligent Safety System, which has been designed to prevent such mistakes from becoming disasters.
The ISS consists of:
* Live circuit warning: Warns of accidental connection to a live circuit greater than 25 V on any range.
* Safe contact detector: Prevents danger during continuity testing if contact is made with a live circuit and minimises the chances of blowing the instruments fuse.
* Test lockout: Prevents test being energised in presence of external voltages.
* Default voltmeter: Displays presence of dangerous voltages on connected circuit irrespective of instrument range selected.
* Auto discharge: Safely discharges connected circuits after insulation test.
Instant response 'Zap' buzzer
The audible buzzer range is frequently used for checking for correct polarity in installed circuits and for point-to-point connectivity in servicing. It is vital that the instrument provides an instant response in such situations. Many insulation testers take up to one second to respond, making them tedious and frustrating in use. The Megger BMM500 series features specially designed 'instant response' circuitry some 80 times faster than rival products.
The 'Zap' buzzer also features seven user selectable thresholds, below which the buzzer will sound continuously. At values above the chosen limit, the buzzer will sound an intermittent tone unless the value is above 3 kOhm in which case no sound will be emitted. This provides a useful audible approximation of the value being measured.
DART display
The BM500 series incorporates a large backlit digital LCD display combining digital and analog response technology. This provides the benefits of true analog clarity, (with its ability to spot an momentary insulation breakdown or poor continuity connection), with the stability and simplicity of a digital reading. The display is backlit, enabling use in dimly lit areas, which is especially useful when the installation power is turned off for testing.
Insulation testing
Instruments are available with either one, two or three insulation test voltages to suit all needs.
Whichever model is chosen the ranges are capable of supplying 1 mA test current at the minimum pass levels expressed by 16th Edition Wiring Regulations, (BS7671), IEC364, HD384 and VDE0413 Parts 1 and 4.
Electrical contractors and servicing
The BMM500 series insulation continuity testers has a wide variety of applications for testing electrical installations to both the British and the international wiring regulations. Each instrument conforms to the requirements of Table 71A in BS7671 and to VDE 0413 parts 1 and 4, HD 384, IEC 364 and EN 61557. In addition the range meets the requirements of BSEN 61010-1 for safe connection to a 440 V Installation Category III supply (300 V phase to earth).
The BMM500 series is designed to provide the electrical contractor with a highly functional tool for testing/commissioning fixed installations. The inclusion of a power saving backlight ensures that the display can be clearly seen even where the distribution board is located in a dark cupboard, but without ruining battery life.
Three insulation test voltages of 250, 500 and 1000 V are provided to ensure that the correct test voltage for the installation under test is always available. The 500 V range is suitable for the majority of testing on circuits with a nominal voltage up to 500 V. The 250 V insulation range is necessary where low voltage circuits supplied by an isolating transformer are tested whilst the 1000 V range is used for circuits with a nominal voltage exceeding 500 and below 1000 V.
The instruments have a 200 mA continuity range which is ideal for testing the continuity of ring final circuit conductors, primary bonding of services and of supplementary bonding conductors. The zero offset adjustment allows the resistance of the test leads to be ignored so the measurement shown is due to the conductors under test only.
To aid operation in awkward situations where the instrument cannot be held in one hand the Megger SP1 switched probe is available to facilitate control of the instrument test button directly from the probe. In addition to the electrical features above, the rugged design of the BMM500 range ensures that they can withstand the everyday handling, transportation and storage with other tools in the contractor's tool bag.
Servicing
The BMM500 series is well suited to the service industry, since they offer a comprehensive range of features in a single unit. The insulation ranges are useful for establishing the integrity of the internal parts such as motors, timers and transformers whilst the continuity range can verify the correct earth bonding of the case metalwork etc.
Voltage and resistance ranges find a multitude of uses in the measurement of component parts within consumer appliances, such as the verification of correct mains supplies timer-switching characteristics and component level measurements on control PCBs.
The unique probe range enables the BMM500 series to interface to a range of probes for measurement of the various parameters such as temperature, which is useful for verifying the correct operation of items such as oven thermostats, or the measurement of heated air temperature and humidity to be made.
Continuity testing
A hands-free 200 mA continuity test range meeting the requirements of UK and European legislation is also included to ensure the accurate measurement of circuit final conductors and primary and supplementary bonding.
Test lead zeroing
The continuity range has a facility to automatically remove the resistance of the test leads from the measured value, a task that would normally have to be done manually. This ensures that the measurement displayed is due entirely to the conductors under test.
The insulation and continuity ranges are augmented by a number of additional measurement ranges such as auto-ranging voltage measurement up to 600 V a.c./d.c. and kOhm resistance measurement enabling a toolbag environment and also comes complete with durable carry pouch with provision for storage of all leads.
Additional servicing measurements
The BMM500 series supports the connection of virtually any mV probe. Such devices extend the range of possible measurements almost endlessly including such items as temperature probes, air-speed indicators and high current clampmeters such as used in heating and ventilation (HVAC), and servicing.
Spescom MeasureGraph, a division of JSE-listed Spescom, is the sole local distributor of the AVO product range.
Kevin Preston, Spescom MeasureGraph
011 266 1500
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