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 CAT
Ⅰ
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 % r 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