Brymen BM251s User manual

USER'S

MANUAL

BM251s

BM252s

BM255s

BM257s

1) SAFETY

Terms in this manual

WARNING identifies conditions and actions that could result in serious injury or even death to

the user.

CAUTION identifies conditions and actions that could cause damage or malfunction in the

instrument.

This manual contains information and warnings that must be followed for operating the instrument

safely and maintaining the instrument in a safe operating condition. If the instrument is used in a

manner not specified by the manufacturer, the protection provided by the instrument may be

impaired. The meter is intended only for indoor use.

The meter protection rating, against the users, is double insulation per IEC/UL/EN61010-1 Ed. 3.0,

IEC/EN61010-2-030 Ed. 1.0, IEC/EN61010-2-033 Ed. 1.0, IEC/UL/EN61010-031 Ed. 1.1 and

CAN/CSA-C22.2 No. 61010-1-12 Ed. 3.0 to Category II 1000V, CAT III 600V and CAT IV 300V AC

& DC.

Terminals (to COM) measurement category:

V / mAA / A :Category II 1000V, CAT III 600V and CAT IV 300V AC & DC.

Per IEC61010-1 2nd Ed. (2001) Measurement Category

Measurement Category IV (CAT IV) is for measurements performed at the source of the low-

voltage installation. Examples are electricity meters and measurements on primary overcurrent

protection devices and ripple control units.

Measurement Category III (CAT III) is for measurements performed in the building installation.

Examples are measurements on distribution boards, circuit- breakers, wiring, including cables,

bus-bars, junction boxes, switches, socket-outlets in the fixed installation, and equipment for

industrial use and some other equipment, for example, stationary motors with permanent

connection to the fixed installation.

Measurement Category II (CAT II) is for measurements performed on circuits directly connected

to the low voltage installation. Examples are measurements on household appliances, portable

tools and similar equipment.

WARNING

To reduce the risk of fire or electric shock, do not expose this product to rain or moisture. To avoid

electrical shock hazard, observe the proper safety precautions when working with voltages above

60 VDC or 30 VAC rms. These voltage levels pose a potential shock hazard to the user. Do not

touch test lead tips or the circuit being tested while power is applied to the circuit being measured.

Keep your fingers behind the finger guards of the test leads during measurement. Inspect test

leads, connectors, and probes for damaged insulation or exposed metal before using the

instrument. If any defects are found, replace them immediately. Do not measure any current that

exceeds the current rating of the protection fuse. Do not attempt a current measurement to any

circuit where the open circuit voltage is above the protection fuse voltage rating. Suspected open

circuit voltage should be checked with voltage functions. Never attempt a voltage measurement

with the test lead inserted into the A/mA or A input jack. Only replace the blown fuse with the

proper rating as specified in this manual. Only use the test lead provided with the equipment or UL

Listed Probe Assembly rated CAT III 1000V or better.

CAUTION

Disconnect the test leads from the test points before changing functions. Always set the instrument

to the highest range and work downward for an unknown value when using manual ranging mode.

INTERNATIONAL ELECTRICAL SYMBOLS

Caution ! Refer to the explanation in this Manual

Caution ! Risk of electric shock

Earth (Ground)

Double Insulation or Reinforced insulation

Fuse

AC--Alternating Current

DC--Direct Current

2) CENELEC DIRECTIVES

The instruments conform to CENELEC Low-voltage directive 2006/95/EC and Electromagnetic

compatibility directive 2004/108/EC

3) PRODUCT DESCRIPTION

Note: Top of the line model is used as representative for illustration purposes. Please refer to your

respective model for function availability.

1) 3-5/6 digits 6000 counts LCD

display

2) Push-buttons for special

functions & features

3) Selector to turn the Power

On or Off and Select a function

4) Input Jack for milli-amp and

micro-amp current functions

5) Input Jack for all functions

EXCEPT current (A, mA, A)

functions

6) Common (Ground reference)

Input Jack for all functions

7) Input Jack for 10A (20A for

30sec) current function

Analog bar-graph

The analog bar graph provides a visual indication of measurement like a traditional analog meter

needle. It is excellent in detecting faulty contacts, identifying potentiometer clicks, and indicating

signal spikes during adjustments.

Average sensing RMS calibrated

RMS (Root-Mean-Square) is the term used to describe the effective or equivalent DC value of an

AC signal. Most digital multimeters use average sensing RMS calibrated technique to measure

RMS values of AC signals. This technique is to obtain the average value by rectifying and filtering

the AC signal. The average value is then scaled upward (calibrated) to read the RMS value of a

sine wave. In measuring pure sinusoidal waveform, this technique is fast, accurate and cost

effective. In measuring non-sinusoidal waveforms, however, significant errors can be introduced

because of different scaling factors relating average to RMS values.

True RMS

True RMS is a term which identifies a DMM that responds accurately to the effective RMS value

regardless of the waveforms such as: square, sawtooth, triangle, pulse trains, spikes, as well as

distorted waveforms with the presence of harmonics. Harmonics may cause :

1)Overheated transformers, generators and motors to burn out faster than normal

2)Circuit breakers to trip prematurely

3)Fuses to blow

4)Neutrals to overheat due to the triplen harmonics present on the neutral

5)Bus bars and electrical panels to vibrate

Crest Factor

Crest Factor is the ratio of the Crest (instantaneous peak) value to the True RMS value, and is

commonly used to define the dynamic range of a True RMS DMM. A pure sinusoidal waveform

has a Crest Factor of 1.4. A badly distorted sinusoidal waveform normally has a much higher Crest

Factor.

4) OPERATION

CAUTION

Before and after hazardous voltage measurements, test the voltage function on a known source

such as line voltage to determine proper meter functioning.

AutoCheckTM mode (models 257s & 255s only)

This innovative AutoCheckTM feature automatically selects measurement function of DCV, ACV or

Resistance () based on the input via the test leads.

●With no input, the meter displays “Auto” when it is ready.

●With no voltage signal but a resistance below 10M(nominal) is present, the meter displays the

resistance value. When the resistance is below “Audible Threshold”, the meter further gives a

continuity beep tone.

●When a signal above the voltage threshold of 1V DC or AC up to the rated 1000V is present, the

meter displays the voltage value in appropriate DC or AC, whichever larger in peak magnitude.

Note:

*Range-Lock and Function-Lock Feature: When a measurement reading is being displayed in

AutoCheckTM mode, press the RANGE or SELECT button momentarily 1 time can lock the range

or function it was in. Press the button momentarily repeatedly to step through the ranges or

functions.

*As Hazardous-Alert: When making resistance measurements in AutoCheckTM mode, an

unexpected display of voltage readings alerts you that the object under test is being energized.

*Ghost-voltage Buster: Ghost-voltages are unwanted stray signals coupled from adjacent hard

signals, which confuse common multimeter voltage measurements. Our AutoCheckTM mode

provides low (ramp-up) input impedance (approx. 2.5kΩ at low voltage) to drain ghost voltages

leaving mainly hard signal values on meter readings. It is an invaluable feature for precise

indication of hard signals, such as distinguishing between hot and open wires (to ground) in

electrical installation applications.

WARNING:

AutoCheckTM mode input impedance increases abruptly from initial 2.5kΩ to a few hundred kΩ’s

on high voltage hard signals. “LoZ” displays on the LCD to remind the users of being in such low

impedance mode. Peak initial load current, while probing 1000VAC for example, can be up to

566mA (1000V x 1.414 / 2.5kΩ), decreasing abruptly to approx. 3.8mA (1000V x 1.414 / 375kΩ)

within a fraction of a second. Do not use AutoCheckTM mode on circuits that could be damaged by

such low input impedance. Instead, use rotary selector or high input impedance voltage

modes to minimize loading for such circuits.

DCV, ACV, & Line Frequency functions

Press the Hz push-button for one second or more to activate or to exit Hz.

DCV

JACK

ACV

JACK

Note:

*Input sensitivity varies automatically with function range selected before activating the Hz

function. 6V function range has the highest and the 1000V range has the lowest. It is

recommended to first measure the signal voltage (or current) level then activate the Hz function in

that voltage (or current) range to automatically set the most appropriate trigger level. You can also

press the RANGE button momentarily to select another trigger level manually. If the Hz reading

becomes unstable, select lower sensitivity to avoid electrical noise. If the reading shows zero,

select higher sensitivity.

*Number of Bar-graph pointer is used to indicate input range (sensitivity) selected. 1/2/3/4 pointers

indicate 6/60/600/1000V, 6/10/-/-A, 60/600/-/-mA or 600/6000/-/-uA is selected in corresponding V,

A, mA or uA function respectively. ( “-”means range not available)

*The Hz of mV function is designed specially for logic level (3V or 5V family) frequency

measurement.

Resistance, Continuity, Capacitance (models 257s, 255s & 252s only), &

Diode test functions

Press the SELECT button momentarily to select the subject functions in sequence. Last selection

will be saved as power up default for repeat measurement convenience.

CAUTION

Discharge capacitors before making any measurement. Large value capacitors should be

discharged through an appropriate resistance load.

CAUTION

Using resistance and continuity function in a live circuit will produce false results and may damage

the instrument. In many cases the suspected component must be disconnected from the circuit to

obtain an accurate reading

Continuity function is convenient for checking wiring connections and operation of switches. A

continuous beep tone indicates a complete wire.

Normal forward voltage drop (forward biased) for a good silicon diode is between 0.400V to

0.900V. A reading higher than that indicates a leaky diode (defective). A zero reading indicates a

shorted diode (defective). An OL indicates an open diode (defective). Reverse the test leads

connections (reverse biased) across the diode. The digital display shows OL if the diode is good.

Any other readings indicate the diode is resistive or shorted (defective).

DCmV, ACmV, Temperature oC & oF functions (models 257s, 255s & 252s only)

Press the SELECT button momentarily to select the subject functions in sequence. Last selection

will be saved as power up default for repeat measurement convenience.

Note: Be sure to insert the banana plug K-type temperature bead probe Bkp60 with correct

polarities. You can also use a plug adapter Bkb32 (Optional purchase) with banana pins to K-type

socket to adapt other standard K type mini plug temperature probes.

A, mA, and A Current functions

Press SELECT button momentarily to toggle between DC and AC.Last selection will be saved as

power up default for repeat measurement convenience.

*Note: When measuring a 3-phase system, special attention should be taken to the phase-to-

phase voltage which is significantly higher than the phase-to-earth voltage. To avoid exceeding the

voltage rating of the protection fuse(s) accidentally, always consider the phase-to-phase voltage as

the working voltage for the protection fuse(s).

Electric Field EF-Detection

At Volt or Current function, press the EF button for one second or more and release to toggle to

EF-Detection feature. The meter displays “E.F.” when it is ready. Signal strength is indicated as a

series of bar-graph segments on the display plus variable beep tones.

●Non-Contact EF-Detection: An antenna is located along the top-right end of the meter, which

detects electric field surrounds current-carrying conductors. It is ideal for tracing live wiring

connections, locating wiring breakage and to distinguish between live or earth connections.

●Probe-Contact EF-Detection: For more precise indication of live wires, such as distinguishing

between live and ground connections, use the Red (+) test probe for direct contact measurements.

PC computer interface capabilities

The instrument equips with an optical isolated interface port at the meter back for data

communication. Press HOLD button while turning the meter on to enable meter PC-COMM output.

Optional purchase PC interface kit BRUA20X is required to connect the meter to the PC computer

RS232 or USB ports.

MAX/MIN at Fast 20/s measurement mode (models 257s & 255s only)

Press REC button momentarily to activate MAX/MIN recording mode. The LCD “MAX MIN” turn

on, and the reading update rate will be increased to 20/second. The meter beeps when new MAX

(maximum) or MIN (minimum) reading is updated. Press the button momentarily to read the MAX

and MIN readings in sequence. Press the button for 1 second or more to exit MAX/MIN recording

mode. Auto-ranging remains, and Auto-Power-Off is disabled automatically in this mode.

5ms CREST capture mode (models 257s & 255s only)

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