HP-37A
DIGITAL MULTIMETER
OPERATOR’S MANUAL
1. Overview
The multimeter is characterized at slim size, portable, stable performance
and anti-dropping capacity. Using 3 1/2 digits LCD monitor with character
28mm high, they offer clear readings. With overall circuitry design
centering on large-scale IC
A
/D converters in conjunction and over-load
protection circuit, the meters give excellent performance and exquisite
making as a handy utility instrument.
The meters can be used to measure DC &
A
C voltage, DC current,
resistance, temperature, battery test, positive diode voltage fall and
audible continuit
y
.
2. Panel Layout
1
Test lead fixture: Fix the test lead.
2
LCD display: 3 1/2 digits LCD display.
3
HOLD key: Press the “HOLD” key to lock display value, and the “DH”
sign will appear on the display, press it again to exit.
4
LIGHT key: Press the “LIGHT” key to light up the LCD backlight,
press it again to exit, it will be automatically turned off too after
approx. 30 seconds. If the battery is in weak power, the light will be
dimmed. Press the key to power on when auto power off.
5
Rotary Switch: Use this switch to select functions and ranges.
6
COM: COM and Temperature “-” Input Jac
k
7
10A: 10AInput Jac
k
8
VΩmA: V/mA/BATT/ andTemperature “+” InputJac
k
9
Crust of meter
10
Protective casing
3. Safety Information
3-1 The meter is designed according to IEC-1010 concerning electronic
measuring instruments with an over-voltage category 600
V
(CAT Ⅲ)and
pollution 2.
3-2 Follow all safety and operating instructions to ensure that the meter is
used safely and is kept in good operating condition.
3-3 safety symbols:
Important safety information, refer to the operating manual.
Dangerous voltage may be presence.
Double insulation (protection Class II)
4. Special Cautions forOperation
4-1 The meters can be safe only according to standard procedures when
used in conjunctions with the supplied test leads. To replace damaged test
leads with only the same model or same electric specifications.
4-2 To avid ris
k
of electric shock, do not use the meters before the cover is
in place.
4-3 The range switch should be right position for the testing.
4-4 To avoid electric shoc
k
and damaging the instruments, the input
signals are forbidden to exceed the specified limits.
4-5 When measuring TV set or switched power, attention should be paid to
the possible pulses that may bring destruction to the circuit.
4-6 Range switch position is forbidden to be changed at random during
measurement.
4-7 Take caution against shock in the course of measuring voltage higher
than DC 60V &
A
C30V.
4-8 Protection fuse should be replaced only with same type and same
specification.
4-9
A
fter operation is finished, set function switch at OFF range to save
battery power.
4-10 If the meter is without usage for long time, take out battery to avoid
damage by battery leakage.
5. GENERAL SPECIFICATIONS
5-1 Max Voltage between input terminal and Earth Ground: CAT Ⅲ 600V
5-2 Over-range Indication: display “1” or “-1” for the significant digit.
5-3
A
utomatic display of negative polarity “-” .
5-4 Low Battery Indication: “
” displayed.
5-5 Display: 3 1/2 digit LCD with a max. reading of 1999.
5-6 Manual range control
5-7
A
uto Power Off: The meter will switch to standby mode when power on
after approx. 30 minutes. Press the LIGHT key or rotate the rotary
switch to OFF position, then power on to exit standby mode.
5-8 Fuse protection: 200mA/250V PPTC Resettable Fuse
5-9 Power supply: 9V battery (6F22 or NED
A
1604)
5-10 Operating Temp.: 0℃ to 40℃ (relative humidity <85%)
5-11 Storage T emp.:-10℃ to 50℃ ((relative humidity <85%)
5-12 Guaranteed precision Temp.: 23±5℃ (relative humidity <70%)
5-13 Dimension: 150x106x36mm
5-14 Weight: approx. 250g (including battery)
6. Testing Specifications
A
ccuracy is specified for a period of year after calibration and at 18℃ to
28℃ (64℉ to 82℉) with relative humidity to 70%.
6-1 DC
V
oltage
Range Resolution Accuracy
2V 1mV
±(0.5% of rdg + 2 digits)
20V 10mV
200V 100mV
600V 1V ±(0.8% of rdg + 2 digits)
-- Impedance: 1MΩ
-- Overload protection: 600V DC or
A
Crms
6-2
ACV
oltage
Range Resolution Accuracy
200V 100mV
±(1.5%ofrdg+5digits)
600V 1V
-- Impedance: 450kΩ
-- Overload protection: 600V DC or
A
Crms
-- Frequency Range: 40 to 400Hz
-- Response: average, calibrated in rms of sine wave
6-3 DC Current
Range Resolution Accuracy
2mA 1μA
±(1.2% of rdg + 2 digits)20mA 10μA
200mA 100μA
10A 10mA ±(2.0% of rdg + 3 digits)
-- Overload protection: 200mA/250V PPTC Resettable Fuse
Note: 10
A
range is not fused, 10Aup to 10 seconds
6-4 Resistance
Range Resolution Accuracy
200Ω 0.1Ω ±(1.0% of rdg + 3 digits)
2kΩ 1Ω
±(1.0% of rdg + 2 digits)20kΩ 10Ω
200kΩ 100Ω
2MΩ 1kΩ ±(1.5% of rdg + 3 digits)
-- Overload protection: 250VDC orACrms
6-5 Temperature
Range Accuracy Resolution
℃
-20~150℃ ±(3℃+ 1digit )
1℃
150~1000℃ ± ( 3% of rdg + 2digits )
-- NiCr-NiSi K-type sensor
-- Overload protection: 200mA/250V PPTC Resettable Fuse
6-6 Battery test
Range
A
ccuracy Load current Resolution
±(5.0% of rdg + 5 digits)
A
pprox. 50mA 1mV
A
pprox. 10mA 10mV
-- Overload protection: 200mA/250V PPTC Resettable Fuse
6-7 Diode and
A
udible continuity test
Range Description Test Condition
Display read approximately
forward voltage of diode
Forward DC current
approx. 1m
A
Reversed DC voltage
approx. 3V
Built-in buzzer sounds if
resistance is less than 50Ω
Open circuit voltage
approx. 3V
Overload protection: 250V DC orACrms
7. OPERATING INSTRUCTIONS
7-1 Attention before operation
7-1-1 Check battery. When the battery voltage drop below proper
operation range, the “
” symbol will appear on the LCD display and the
battery need to changed.
7-1-2 Pay attention to the “
” besides the input jack which shows that the
input voltage or current should be within the specified value.
7-1-3 The range switch should be positioned to desired range for
measurement before operation.
7-2 Measuring DC Voltage
7-2-1 Connect the black test lead to COM jackandtheredtoVΩmA jack.
7-2-2 Set the rotary switch at the desired “V
” range position.
7-2-3 Connect test leads across the source or load under measurement.
7-2-4 You can get reading from LCD. The polarity of the red lead
connection will be indicated along with the DC voltage value.
NOTE:
1. When the value scale to be measured is unknown beforehand, set the range
selector at the highest position.
2. When only the figure “1” or “-1” is displayed, it indicates over-range situation and
the higher range has to be selected.
3. “
” means you can’t input the voltage more than 600V, it’s possible to
show higher voltage, but it may destroy the inner circuit or pose a shock.
4. Be cautious against shock when measuring high Voltage.
7-3 Measuring AC Voltage
7-3-1 Connect the black test lead to COM jackandtheredtoVΩmA jack.
7-3-2 Set the rotary switch at the desired “V
” range position.
7-3-3 Connect test leads across the source or load under measurement.
7-3-4 You can get reading from LCD. The polarity of the red lead
connection will be indicated along with the DC voltage value.
NOTE:
1. When the value scale to be measured is unknown beforehand, set the range
selector at the highest position.
2. When only the figure “1” or “-1” is displayed, it indicates over-range situation and
the higher range has to be selected.
3. “
” means you can’t input the voltage more than 600V, it’s possible to
show higher voltage, but it may destroy the inner circuit or pose a shock.
4. Be cautious against shock when measuring high Voltage.
7-4 Measuring DC Current
7-4-1 Connect the black test lead to COM jackandtheredtotheVΩmA
jack for a maximum 200mA current , for a maximum 10A current, move the
redleadtothe10A jack.
7-4-2 Set the rotary switch at the desired “A
” range position.
7-4-3 Connect test leads in series with the load under measurement.
7-4-4 You can get reading from LCD. The polarity of the red lead
connection will be indicated along with the DC current value.
NOTE:
1. When the value scale to be measured is unknown beforehand, set the
range selector at the highest position.
2. When only the figure “1” or “-1” is displayed, it indicates over-range
situation and the higher range has to be selected.
3. “
” means the socket mA’s maximum current is 200mA and 10A’s
maximum current is 10A, over 200mA current can be protected by the
PPTC resettable fuse, but the 10A range is not fused.
4. On the 10A range, the measuring time should be less than 10 seconds
to prevent precision from affecting by circuit heating.
7-5 Measuring Resistance
7-5-1 Connect the black test lead to COM jackandtheredtoVΩmA jack.
7-5-2 Set the rotary switch at the desired “Ω” range position.
7-5-3 Connect test leads across the resistance under measurement.
7-5-4 You can get reading from LCD.
NOTE: Max. input overload: 250V rms＜10sec
1. When only the figure “1” or “-1” is displayed, it indicates over-range
situation and the higher range has to be selected.
2. For measuring resistance above 1M Ω , the mete may take a few
seconds to get stable reading.
3. When the input is not connected, i.e. at open circuit, the figure “1” or “-1”
will be displayed for the over-range condition.
4. When checking in-circuit resistance, be sure the circuit under test has
all power removed and that all capacitors have been discharged fully.
7-6 Measuring Temperature
7-6-1 Connect the black banana plug of the sensor to COM jack and the
red banana plug to the VΩmA jack.
7-6-2 Set the rotary switch at the desired “
” range position.
7-6-3 Put the sensor probe into the temperature field under measurement.
7-6-4 You can get reading from LCD.
NOTE:
1. The accessory of the meter WRNM-010 type contact thermocouple limit
temperature is 250
(300 shortly), please use special probe for test
higher temperature.
2. Please don't change the thermocouple at will, otherwise we can't
guarantee to measure accuracy.
3. Please don’t importing the voltage in the temperature function.
7-7 Battery Testing
7-7-1 Connect the black test lead to COM jack and the red to VΩmA jack.
7-7-2 Set the rotary switch at the desired “
”or“ ” range position to
test 1.5V or 9V battery.
7-7-3 Connect test leads across the source or load under measurement.
7-7-4 You can get reading from LCD.
7-8 Diode & Audible continuity Testing
7-8-1 Connect the black test lead to COM jack and the red to VΩmA jack.
7-8-2 Set the rotary switch at the “
” range position.
7-8-3 On diode range, connect the test leads across the diode under
measurement, display shows the approx. forward voltage of this diode.
7-8-4 On Audible continuity range, connect the test leads to two point
of circuit, if the resistance is lower than approx. 50Ω, the buzzer sounds.
NOTE: Make sure the power is cut off and all capacitors need to be
discharged under this measurement.
8. Battery replacement
1) When the battery voltage drop below proper operation range the "
"
symbol will appear on the LCD display and the battery need to changed.
2) Before changing the battery, set the selector switch to “OFF”position.
Open the cover of the battery cabinet by a screwdriver.
3) Replace the old battery with the same type battery (9V 6F22 or NEDA
1604).
4) Close the cover of the battery cabinet and fasten the screw.
9. Maintenance
9-1 Before attempting to remove the battery door or open the case, be
sure that test leads have been disconnected from measurement circuit top
avoid electric shock hazard.
9-2 You must replace the test leads if the lead is exposed, and should
adopt the leads with the same specifications as origin.
9-3 Use only moist fabric or small amount of detergent but not chemical
solution for cleaning.
9-4 Do not use the meter before the back cover is properly closed a nd
screw secured. Upon any abnormality, stop operation immediately and
send the meter for maintenance.
9-5 Please take out the battery when not using for a long time.
10. Accessories
[1] Test Leads: electric rating 1000V 10A
[2] “K” type thermocouple sensor probe
[3] Operator’s Manual
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