SZBJ BM920 Series User manual

1
BM920 Operating Instruction
I Overview
The complete machine circuit design of BM920 series takes large-scale
integrated circuit and A/D converter as the core, provided with global function
overloading protection to measure direct current voltage and current, A.C. voltage
and current, resistor and current, resistor, capacitor, frequency temperature,
diode forward voltage drop, transistor hFE parameters and circuit on and off ,
Infrared remote control signal detection and Identification of live wire etc.
II Safety rules and attentions
The instrument of model BM920 is in line with IEC1010-1 CATⅠ 1000V
standard. Before use, please read the instruction manual carefully.
It is not allowed to use with the rear cover not ready; otherwise, it may cause
danger.
Before use, check insulation layer of the pen-shape meter shall be perfect and
free of damage and broke wires.
The range switch shall be set at the correct range position.
The input signal can not be beyond the specified limits to avoid electric shock
and damaging the instrument.
Shift of the range switch can not be changed during measuring.
Measure potential difference of the public terminal COM and the ground “
“ can not exceed 600V to avoid electric shock.
For testing voltage higher than DC50V and AC36Vrms, be careful to avoid
electric shock.
When the LCD displays “ ”, electric quantity of the battery is not sufficient,
and the battery shall be replaced to ensure normal operation of the instrument.
Replacement of fuse in the instrument shall employ the same specifications.
The instrument shall be calibrated once a year at least.
III Performance
1. Insufficient electric quantity indication: “‘”.
2. Maximum display: 1999（3 1/2 bit）.
3. Automatic switching off: automatically cut off power supply after
switching on the machine about 15 minutes.
4. 10A jack: without fuse.
5. mA jack fuse: 0.2A/250V Self-recovery fuse.
6. Battery in the unit: 9V NEDA or 6F22 or equivalence.
7. Environmental conditions:
1） Working temperature: 0℃～40 ℃ RH<75%
2） Storage temperature: -10℃～50 ℃RH<85 %
IV Technical indexes
Precision ± (a % reading + figures） Warranty period: 1 year
Guaranteed temperature precision: 23℃±5℃ RH<70 %
1. Direct current voltage
Range Resolution Measurement error
200mV 0.1mV
2V 1mV
20V 10mV
200V 100mV
±（0.5%+5d）
1000V 1V ±（0.8%+5d）
Input impedance: 200mV and 2V shift is 1MΩ, and others are 10MΩ.
Overloading protection: 200mV and 2V range is 250V, and others are
direct or A.C. PEAK 1000V.
2. A.C. voltage
Measurement error Range Resolution
BM9205 BM9208
200mV 0.1mV ±（1.2%+5d） _
2V 1mV _
20V 10mV
200V 100mV
±（0.8%+5d）
±（0.8%+5d）
700V 1V ±（1.2%+7d）
Input impedance: 200mV and 2V range is 1MΩ, and others are 10MΩ.
Frequency scope: 40Hz～400Hz (200V and 700V ranges are 40Hz～100Hz).
Overloading protection: 200mV and 2V ranges are 250V, and others are direct
current or alternative current peak value1000V.
Display: average value (sine wave valid value calibration).
3. Direct current
Range Resolution Measurement error
20uA 0.01μA ±（1.2%+5d）
20mA 10μA ±（0.8%+5d）
200mA 100μA ±（1.2%+5d）
10A 10mA ±（2%+5d）
Overloading protection: 0.2A/250V fuse and 10A range without fuse.
Maximum input current: 10A (input time no more than 10 seconds).
Measuring voltage drop: the full range is DC200mV.
4. Alternative current
Measurement error Range Resolution
BM9205 BM9208
20mA 10μA ±（1.2%+5d） _
200mA 100μA ±（1.8%+5d）
10A 10mA ±（3%+7d）
Overloading protection: 0.2A/250V with fuse, and 10A range without fuse
Maximum input current: 10A (input time no more than 10 seconds)
Measuring voltage drop: the full range is 200mV.
Frequency scope: 40Hz～400Hz.
Display: average value (sine wave valid value calibration)
5. Resistance
Range Resolution Measurement error
200Ω 0.1Ω
2KΩ 1Ω
20KΩ 10Ω
200KΩ 100Ω
2MΩ 1KΩ
±（0.8%+5d）
20MΩ 10KΩ ±（1%+5d）
200MΩ 100KΩ ±（5%+10d）-10d
Overloading protection: 220V valid value
Open circuit voltage:＜1V (200MΩ range is 2.8V)
About 10 displayed in case of short circuit for 200MΩ range: actual measurement
value = display value -10
For example: the measured standard resistance is 100MΩ, the instrument display
is 101.0 and the real value is 101.0 - 10 = 100.0
6. Capacitance Cx
Range Resolution Measurement error
20nF 10pF
200nF 100pF
2μF 1nF
±（2.5%+20d）
200μF 100nF ±（5%+10d
Overloading protection: 36V DC or peak value
7. Frequency F
Measurement error Range Resolution
BM9208
2KHz 1Hz
20KHz 10Hz ±（1.5%+5d）
Notes: valid value of the tested frequency signal: 300mV~50V
Overloading protection: 220V valid value
8. Temperature℃
Measurement error Range Resolution
BM9208
-20～400℃ 1℃ ±（0.75%+4d）
401℃～1000℃ 1℃ ±（1.5%+15d）
Notes: model K thermal coupler is used (temperature probe).
9. Crystal triode hFE testing
Range Notes Testing conditions
hFE
Displayed scope
0～1000β
Ibo≈10μA,
Vce≈2.8V
10. Diode and buzzing continuous conductance testing
Range Notes Testing conditions
Display forward conductance
round value of diode
Forward direct current about
1mA
Backward direct current voltage
about 2.8V
When the conductance
resistance is ＜ about 50Ω
,
buzzer in the machine works,
and round value of the
resistance is displayed.
Open circuit voltage about 2.8V
Overloading protection: 220V valid value
11. Infrared remote control signal detection ( ) and Identification of live wire
(▲) See instructions
V Operation instructions
Before use, pay attention to the symbol beside the jacket of the testing pen
“ ”, which reminds you the tested voltage or current not beyond this value. In
addition, before use, the range switch shall be set at the switch which you want
to set.
1. D.C. voltage measurement

2
1）The black lead is inserted into COM jacket, and the red lead is inserted
into V/Ω jacket.
2）Estimate maximum value of the tested signal voltage, select proper range,
and connect the leads to the tested load or signal source to read the
value.
In addition: polarity of the red pen will be simultaneously displayed on the
screen.
Notes:
a. Before measurement, if range of the tested voltage can not be estimated,
the range switch shall be set at the maximum range shift (1000V shift), and
select proper shift according to the displayed value.
b. If the screen only displays 1, it means that the tested voltage is beyond the
range and voltage higher than 1000V can not be input. Although reading
can be acquired, there is danger of damaging internal wires and causing
safety accidents.
c. Avoid electric shock when measuring high voltage.
2．A.C voltage measurement
1) The black lead is inserted into COM jacket, and the red lead is inserted into
V/Ω jacket.
2) Estimate maximum value of the tested signal voltage, select a proper range
and connect the leads to the tested load or signal source to read the value.
Notes:
Please refer to the D.C. voltage notes a, b and c.
3．D.C. current measurement
1) The black lead is inserted into COM jacket. When the tested current is less
than 200mA, the red lead is inserted into mA jacket; when the tested current is
200mA～10A, the red lead is inserted into 10A jacket.
2) Set the range switch at the range of the D.C. current range, and the leads is
connected with the circuit in series connection. When the instrument displays the
current reading, polarity of the red pen will be displayed.
Notes:
a. Before measurement, if the range of the tested current can not be estimated,
set the range switch at the maximum range switch (10A shift), and select a
proper shift according to the displayed value.
b. If the screen only displays 1, it means that the tested current is beyond the
range, and the range switch shall be shifted higher.
c. Maximum input current of mA jacket is 200mA
d. 10A jacket is not provided with fuse, the measurement time shall be less than
10 seconds to avoid precision affected by heating of wires.
4．A.C. current measurement
1) The black lead is inserted into COM jacket. When the tested current is less
than 200mA, the red lead is inserted into mA jacket; if the tested current is
200mA～10A, the red lead is inserted into 10A jacket.
2) Set the range switch at the A.C. current range scope, and the leads is
connected with the tested circuit in series connection.
Notes:
Refer to the D.C. current measurement notes a, b, c and d.
5．Resistance measurement
1) The black lead is inserted into COM jacket, and the red lead is inserted into
V/Ω jacket.
2) Set the range switch at Ω range scope, and the leads is connected with the
tested circuit in bridge connection.
Notes:
a. When the tested resistance >1MΩ, reading of the instrument can be stabilized
after several seconds, which is normal for measuring high resistance.
b. When measuring high resistance, the resistor shall be inserted into V/Ω and
COM jackets to avoid interference.
c. When testing online resistors, please confirm that the tested circuit is powered
off and the capacitor is fully discharged, and the measurement can be carried out.
d. In case of short circuit, the range 200MΩ has about indicated value 10, which
will be subtracted when measuring. For example, when measuring 100 MΩ
resistance, and the displayed value is 101.0, and the results are 101.0 - 10=100.0
6．Capacitance measurement
1) The black lead is inserted into COM jacket, and the red lead is inserted into
mA jacket.
2) Set the range switch at F range scope, and the leads is connected with the
tested circuit in bridge connection.
Notes:
a. Before connecting the capacitor, the instrument can be calibrated at zero;
however, several indicated value can not affect the testing precision.
b. Do not connect external voltage or the charge capacitor to the input jacket.
When electric quantity of the capacitor is large enough, it will discharge to the
internal instrument, and the measurement precision is affected, and even the
instrument may be burnt down.
7．Frequency measurement（Only available forBM9208）
1) The black lead is inserted into COM jacket, and the red lead is inserted into
V/Ω jacket.
2) Select a proper range, and the leads is parallelly connected to the tested signal
to read the value.
Notes:
a. Valid value of input voltage value of the frequency shift is 200mV to 10V.
b. Maximum value of the input protection voltage is 220V.
8．Temperature measurement (Only available for BM9208)
1）Red end of model K temperature probe is inserted into mA jacket and the
black end is inserted into COM jacket.
2）The probing end (also called thermal end) is placed at the forecast
environment to observe the instrument reading.
Notes:
a. When the temperature shift is suspended at the input end, it displays a random
value, and temperature of the tested environment can be displayed after the
temperature probe is inserted.
b. When the temperature probe is not inserted into the instrument, the displayed
value is meaningless. Limit temperature of the accompanied model K
WRNM-010 exposed contact thermal coupler is 250℃ (300℃ for a short while).
9．Crystal triode hFE parameters measurement
1) Set the range switch at hFE shift.
2) Confirm the crystal triode is PNP or NPN, and pins E, B and C of the tested
tube is inserted into the testing holes of the instrument.
3)The instrument displays hFE round value, and the testing conditions are base
current 10μA and Vce about 2.8V.
10．Diode measurement
1) The black lead inserted into COM jacket, and the red lead is inserted into V/Ω
jacket (polarity of the red pen is “+”).
2) Set the range switch at , and the testing leads is connected with the tested
diode in bridge connection.
Notes:
a. When the input end is open circuit, the instrument displays 1, which is beyond
the range.
b. The displayed value is forward voltage drop value. When the diode is
connected in a reverse direction, it is beyond the range.
11．Buzzing continuity conductance testing
1) The black lead is inserted into COM jacket, and the red lead is inserted into
V/Ω jacket.
2) Set the range switch at range (the same shift with diode testing),
and the leads is connected with both ends of the circuit be tested in bridge
connection.
3) If resistance between the tested points is less than 50Ω, the buzzer will work.
Notes:
Conductance of the tested circuit must be checked with power off. For any
loading signal will make the buzzer make sound which causes error judgment.
12. Infrared remote control signal detection ( )
This shift is set up for measuring whether the infrared remote control
transmitter is working properly. When on the shift, Vertically align the transmiting
head of the infrared remote control transmitter to the infrared receiver below
the power switch, and keep the deviation not more than ±15o , and then press
down the remote control button. If the red LED flashes, indicate that the
transmitter is working correctly. Move the transmitter in a certain distance
(i.e.1-30cm) to be able to measure the state of the output power of the
transmitter.
Note：1. When the reciver head is exposed directly under strong light, the red
indicator will be on, and the light intensity of red indicator will be changed with
the strong /weak of the light (This is the reference for Illuminance Meter ), so
when only detect the infrared remote controller, the reciver of the multimeter
should be kept away from strong light source.
2. The transmiting head of the remote controller must be perpendicular to the
infrared receiver of the meter.( Maximum deviation angle is±15o )
13. Identification of live wire (▲)
The red pen is inserted into V/Ω jacket, and the black pen is inserted into COM
jacket. Take the insulated part of the black pen by one hand, and do not
connected to the line to be tested; ▲ is displayed in the meter when the red pen
is connected to the live wire, and ▲ is not displayed in the meter when the red
pen is connected to the zero line or the grounding.
Special note: The identification symbol "▲" of the live wire can not be kept.
14．Data holding
When pressing DH key, the data is held on the screen; when the DH key is
released, it enters normal measurement conditions again.
Special note: The identification symbol "▲" of the live wire can not be kept.
VI Accessories
1. 1 Instruction manual
2. 1 couple of pen meters
3. 1 piece of PVC protection sleeve
4. Temperature probe of model K (Only available for BM9208）