REED ST-9918T User manual

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Model ST-9918T
True RMS Autoranging
Digital Multimeter
Instruction
Manual

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Table of Contents
Safety ............................................................................................ 3
Display Symbol Descriptions ........................................................ 4
Operating Instructions..............................................................5-10
Button Functions .....................................................................5-6
DC/DC Voltage Measurement ..................................................... 7
DC Current Measurement ........................................................... 7
AC Current Measurement ........................................................7-8
Resistance (Ω) Measurement ...................................................... 8
Continuity Check......................................................................... 8
Diode Test................................................................................... 9
Capacitance Measurement ......................................................... 9
Frequency Measurement .......................................................... 10
Temperature Measurement ....................................................... 10
Specications.........................................................................10-14
Technical..............................................................................10-11
Accuracy .............................................................................12-14
Battery & Fuse Replacement....................................................... 15
For service on this or any other REED product, contact REED Instruments
at [email protected].

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Safety
The following safety information must be observed to insure maximum
personal safety during the operation at this meter:
• Measurements beyond the maximum selected range must not be at-
tempted.
• Extreme care must be taken when measuring above 50 V, especially on
live bus-bars.
• To measure voltage, the instrument must not be switched to a current or
resistance range, or to the diode check or buzzer position.
• Circuits must be de-energized and isolated before carrying out resis-
tance tests.
• The rotary selector switch must only be turned after removing test con-
nections.
• All external voltages must be disconnected from the instrument before
removing the battery.
• Test leads and prods must be in good order, clean, and with no broken
or cracked insulation.
• UK Safety Authorities recommend the use of fused test leads when
measuring voltage on high energy systems.
• Replacement fuses must be of the correct type and rating.
• The instrument must not be used if any part of it is damaged.
• Warnings and precautions must be read and understood before an
instrument is used. They must be observed during the operation of this
instrument.

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Safety Symbols:
CAUTION refer to accompanying notes. This symbol indicates
that the operator must refer to an explanation in the Operating
Instructions to avoid personal injury or damage to the meter.
CAUTION risk of electric shock. This WARNING symbol
indicates a potentially hazardous situation, which if not
avoided, could result in death or serious injury.
This symbol advises the user that the terminal(s) so marked must
not be connected to a circuit point at which the voltage with
respect to earth ground exceeds (in this case) 1000 VAC or VDC.
Equipment protected throughout
by Double Insulation (Class II)
Equipment complies with current EU directives.
Display Symbol Descriptions
Continuity
BAT Low Battery
Diode test
HOLD Data Hold
AUTO AutoRanging
AC Alternating Current or Voltage
DC Direct Current or Voltage
MAX/MIN Stores the highest or lowest measurement
PEAK Find glitches and transients without a scope
Backlight
V Volts
A, mA,uA Current range
MAX

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Operating Instructions
To turn on the instrument turn the range knob from the OFF position to
any measurement range.
• For the best battery life ALWAYS turn the function switch to the OFF
position when the meter is not in use. This meter has Auto OFF that
automatically shuts the meter OFF after 30 minutes of elapsed time.
• On some low AC and DC voltage ranges, with the test leads not con-
nected to a device, the display may show a random, changing reading.
This is normal and is caused by the high-input sensitivity. The reading will
stabilize and give a proper measurement when connected to a circuit.
MODE button
To select AC or DC measurement when in Voltages, Amps, mA , uA ,Ω,
, ,°C or °F ranges.
HOLD button
The HOLD function allows the meter to “freeze” a measurement for later
reference.
1. Press the HOLD button to “freeze” the reading on the indicator.
The “HOLD” message will be appear in the display.
2. Press the HOLD button again to return to normal operation.
BACKLIGHT button
1. Press the BACKLIGHT button to switch on the display light.
2. Press BACKLIGHT button again to exit the light mode.
MAX/MIN button
The MAX/MIN function allows the meter to capture the highest or lowest
measurement for later reference.
1. Press the MAX/MIN button to begin measurement.
The indicator “MAX” or MIN will appear in the display.
2. If the “MAX MIN” messages are ashing, the instrument is in MAX/MIN
mode but not recording, press the MAX/MIN button to select a mode.
3. To return to normal AUTO measurement mode, hold down the
MAX/MIN button for 2 seconds.

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Peak Hold button
The Peak Hold function captures the peak AC or DC voltage or current.
The meter can capture negative or positive peaks as fast as 1 millisecond
in duration.
1. Turn the function switch to the A or V position.
2. Use the MODE button to select AC or DC.
3. Allow time for the display to stabilize.
4. Press and Hold the PEAK button until “CAL” appears in the display.
This procedure will zero the range selected.
5. Press the PEAK button, Pmax will display.
6. The display will update each time a higher positive peak occurs.
7. Press the PEAK button again, Pmin will display. The display will now
update and indicate the lowest negative peak.
8. To return to normal operation, press and hold the PEAK button until
the Pmin or Pmax indicator switches off.
NOTE: If the Function switch position is changed after a calibration the
Peak Hold calibration must be repeated for the new function
selected.
RANGE button
When the meter is rst turned on, it automatically goes into AutoRanging.
This automatically selects the best range for the measurements being
made and is generally the best mode for most measurements.
For measurement situations requiring that a range be manually
selected, perform the following:
1. Press the RANGE button. The “Auto Range” display indicator will
turn off, The “Manual Range” display indicator will turn on
2. Press the RANGE button to step through the available ranges until
you select the range you want.
3. Press and hold the RANGE button for 2 seconds to exit the
ManualRanging mode and return to AutoRanging.

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DC/DC Voltage Measurement
1. Insert the black test lead into the negative COM terminal and the red
test lead into the positive V terminal.
2. Set the function switch to the VAC or VDC position.
3. Use the MODE button to select AC or DC Voltage
4. Connect the test leads in parallel to the circuit under test.
5. Read the voltage measurement on the LCD display
DC Current Measurement
1. Insert the black test lead banana plug into the negative (COM) jack.
2. For current measurements up to 4000uA DC, set the function switch to
the uA position and insert the red test lead banana plug into the (uA) jack.
3. For current measurements up to 400mA DC, set the function switch to the
mA range and insert the red test lead banana plug into the (mA) jack.
4. For current measurements up to 10A DC, set the function switch to the
A position and insert the red test lead banana plug into the 10A jack.
5. Press the AC/DC button until “DC” appears in the display.
6. Remove power from the circuit under test, then open up the circuit at
the point where you wish to measure current.
7. Touch the black test probe tip to the negative side of the circuit. Touch
the red test probe tip to the positive side of the circuit.
8. Apply power to the circuit.
9. Read the current in the display. The display will indicate the proper
decimal point, value and symbol.
AC Current Measurement
1. Insert the black test lead plug into the negative (COM) socket.
2. For current measurements up to 10A, set the function switch to the A
position and insert the red test lead plug into the (10A) jack.
3. For current measurements up to 400mA, set the function switch to the
mA range and insert the red test lead banana plug into the (mA) jack.
4. For current measurements up to 10A AC, set the function switch to the
A position and insert the red test lead banana plug into the 10A jack.
continued ...

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5. Press the MODE button. The measurement mode will change between
AC or DC as required.
6. Remove power from the circuit under test, then open up the circuit at
the point where you wish to measure current.
7. Touch the black test probe tip to the negative side of the circuit. And
touch the red test probe tip to the positive side of the circuit.
8. Apply power to the circuit.
9. Read the current in the display. The display will indicate the proper
decimal point, value and symbol.
Resistance [ Ω ] Measurement
WARNING: To avoid electric shock, disconnect power to the unit under test
and discharge all capacitors before taking any resistance mea-
surements. Remove the batteries and unplug the line cords.
1. Set the function switch to the Ωposition.
2. Insert the black test lead plug into the negative (COM) socket and the
red test lead plug into the positive Ωjack.
3. Press the MODE button until “Ω” appears in the display.
4. Touch the test probe tips across the circuit or part under test. It is best
to disconnect one side of the part under test so the rest of the circuit
will not interfere with the resistance reading.
5. Read the resistance in the display. The display will indicate the proper
decimal point, value and symbol.
Continuity Check
WARNING: To avoid electric shock, never measure continuity on circuits
or wires that have voltage on them.
1. Set the range switch to the position.
2. Insert the black lead plug into the COM socket and the red test lead
plug into the positive socket.
3. Press the MODE button until “ ” appears in the display.
4. Touch the test probe tips to the circuit or wire you wish to check.
5. If the resistance is less than 35Ω, the audible signal will sound.
The display will also show the actual resistance in ohms.

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Diode Test
WARNING: To avoid electric shock, do not test any diode that has
voltage on it.
1. Set the function switch to the position.
2. Insert the black test lead plug into the COM socket and the red test
lead plug into the socket.
3. Press the MODE button until “ ” appears in the display.
4. Touch the test probe tips to the diode or semiconductor junction you
wish to test. Note the meter reading.
5. Reverse the probe polarity by switching probe position. Note this reading.
6. The diode or junction can be evaluated as follows:
A. If one reading shows a value and the other reading shows OL, the
diode is good.
B. If both readings show OL, the device is open.
C. If both readings are very small or zero, the device is shorted.
NOTE: The value indicated in the display during the diode check is the
forward voltage.
Capacitance Measurement
WARNING: To avoid electric shock, discharge the capacitor under
test before measuring.
1. Set the function switch to the CAP capacitance position.
2. Insert the black test lead banana plug into the negative COM jack and
the red test lead banana plug into the CAP positive jack.
3. Touch the test probe tips across the part under test.
4. Read the capacitance value in the display.
5. The display will indicate the proper decimal point and value.
NOTE: For very large values of capacitance measurement time can be
several minutes before the nal reading stabilizes. The bar graph
is disabled in capacitance measurement mode. The LCD displays
DIS. C .Discharging through the chip is quite slow. We recommend
the user to discharge the capacitor with some other apparatus.

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Frequency Measurement
1. Set the function switch to the Hz position.
2. Insert the black test lead banana plug into the negative (COM) jack and
the red test lead banana plug into the positive Hz jack.
3. Touch the test probe tips to the circuit under test.
4. Read the frequency in the display. The digital reading will indicate the
proper decimal point, symbols (kHz, MHz) and value.
Temperature Measurement
1. Set the function switch to the Type K ºF or ºC position.
2. Insert the Temperature Probe into the input jacks, making sure to
observe the correct polarity.
3. Press the MODE button until “ºF or ºC” appears in the display.
4. Touch the Temperature Probe head to the part whose temperature you
wish to measure. Keep the probe touching the part under test until the
reading stabilizes (about 30 seconds).
5. Read the temperature in the display.
NOTE: The temperature probe is tted with a type K mini connector.
A mini connector to banana connector adaptor is supplied for
connection to the input banana jacks.
Specifications
Technical
Insulation: Class2, Double insulation
Overvoltage category: CATIV 600V,CATIII 1000V
NOTE: These meters meet CAT III and CAT IV IEC 61010 standards.
The IEC 61010 safety standard denes four overvoltage
categories (CAT I to IV) based on the magnitude of danger from
transient impulses. CAT III meters are designed to protect against
transients in xed-equipment installations at the distribution level;
CAT IV meters are designed to protect against transients from the
primary supply level (overhead or underground utility service).

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Maximun voltage
between any terminal
& earth ground: 1000V DC/AC RMS
Surge Protection: 8kV peak IEC 61010
AC TRUE RMS: The term stands for “Root-Mean-Square” which repre-
sents the method of calculation of the voltage or current value. Average
responding multimeters are calibrated to read correctly only on sine waves
and they will read inaccurately on non-sine wave or distorted signals. True
rms meters read accurately on either type of signal.
Display: 4000 counts LCD display, 21mm high
Polarity: Automatic, (-) negative polarity indication.
Over-range: “OL” mark indication.
Low battery indication: The “ ” symbol is displayed when the
battery voltage drops below the operating level
Measurement rate: 2 times per second nominal.
Auto power off: Meter automatically shuts down after approx.
30 minutes of inactivity.
Operating environment: -10°C to 50°C (14°F to 122°F)
at < 70 % relative humidity.
Storage temperature: -30°C to 60°C (-4°F to 140°F)
at < 80 % relative humidity.to
Relative humidity: 90% (0°C to 30°C); 75% (30°C to 40°C);
45% (40°C to 50°C)
For inside use max height: Operating:3000m, Storage 10,000m
Pollution degree: 2
Safety: Complies with IEC/EN 61010-1:2001-02 &
IEC/EN 61010-031:2002
Power: One 9V battery , NEDA 1604, IEC 6F22
Dimensions: 182 (H) x 82 (W) x55 (D) mm
Weight: Approx.: 375g.
Includes: Standard Red/Black lead set with test probes

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Accuracy
Accuracy is given at 18°C to 28°C (65°F to 83°F), less than 70 % RH
DC Voltage (Auto-ranging)
Range Resolution Accuracy
400.0mV 0.1mV +0.5% of rdg + 2 digits
4.000V 1mV
40.00V 10mV
400.0V 100mV
1000V 1V +0.8% of rdg + 2 digits
Input Impedance: 7.8MΩ.
Maximum Input: 1000V dc or 1000V ac rms.
AC Voltage (Auto-ranging)
Range Resolution Accuracy
400.0mV 0.1mV +0.8%of rdg + 3 digits
4.000V 1mV
40.00V 10mV
400.0V 100mV
1000V 1V +1.2%of rdg + 5 digits
Input Impedance: 7.8MΩ.
AC Response: 50 Hz 60Hz
Maximum Input: 1000V dc or 1000V ac rms.
DC Current (Auto-ranging)
Range Resolution Accuracy
400.0uA 0.1uA +1.2% of rdg + 3 digits
4000uA 1uA
40.00mA 10uA
400.0mA 100uA
10A 10mA +2.5% of rdg + 3 digits
Overload Protection: 0.5A / 1000V and 10A / 1000V Fuse.
Maximum Input: 400uA dc on uA range
400mA dc on mA range
10A dc on 10A range.

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AC Current (Auto-ranging)
Range Resolution Accuracy
400.0uA 0.1uA +1.5% of rdg + 5 digits
4000uA 1uA
40.00mA 10uA
400.0mA 100uA
10A 10mA +3.0% of rdg + 5 digits
Overload Protection: 0.5A / 1000V and 10A / 1000V Fuse.
AC Response: 50 Hz to 60 Hz
Maximum Input: 400uA ac rms on uA
400mA ac rms on mA
10A ac rms on 10A range.
Resistance [Ω] (Auto-ranging)
Range Resolution Accuracy
400.0Ω 0.1Ω +0.8% of rdg + 5 digits
4.000kΩ 1Ω +0.8% of rdg + 2 digits
40.00kΩ 10Ω
400.0kΩ 100Ω
4.000MΩ 1kΩ +2.5% of rdg +8digits
40.00MΩ 10kΩ
Input Protection: 1000V dc or 1000V ac rms.
Capacitance (Auto-ranging)
Range Resolution Accuracy
4.000nF 1pF +5.0% of rdg+20 dgts
40.00nF 10pF +5.0% of rdg + 7 dgts
400.0nF 0.1nF
4.000uF 1nF +3.0% of rdg + 5 dgts
40.00uF 10nF
400.0uF 0.1uF
4.000mF 0.001mF +10% of rdg + 10 dgts
40.00mF 10.00mF
Input Protection: 1000V dc or 1000V ac rms.

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Frequency (Auto-ranging)
Range Resolution Accuracy
4.000kHz 1Hz +1.2% of rdg + 3 dgts
40.00kHz 10Hz
400.0kHz 100Hz
10.00MHz 1kHz +1.5% of rdg + 4 dgts
Sensitivity: >0.5V RMS while ≤1MHz
Sensitivity: >3V RMS while >1MHz
Input Protection: 1000V dc or 1000V ac rms.
Temperature
Range Resolution Accuracy
-20°C~+760°C 1°C +3% of rdg +5dgts
-4°F~+1400°F 1°F +3% of rdg +8dgts
Sensor: Type K Thermocouple
Overload protection: 1000V dc or ac rms..
Diode Test
Test current Resolution Accuracy
1Ma typical/
Open MAX.3V 1 mV +10% of rdg + 5 digits
Open circuit voltage: MAX. 3V dc
Overload protection: 1000V dc or ac rms.
Audible continuity
Audible Threshold: Less than35Ω Test current MAX. 1.5mA
Overload Protection: 1000V dc or ac rms.

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Battery & Fuse Replacement
WARNING: To avoid electric shock, disconnect the test leads from any
source of voltage before removing the battery or fuse cover.
Do not operate your meter with the cover removed. Be sure
it is in place and fastened securely.
Battery Replacement
When the battery level gets low or falls below the operating voltage, the
battery warning symbol “ ” will appear in the LCD display.
1. Disconnect the test leads from the meter.
2. Open the battery cover by loosening the screw using a Phillips head
screwdriver.
3. Insert the battery into battery holder, observing the correct polarity.
4. Put the battery cover back in place. Secure with the two screws.
NOTE: If your meter does not work properly, check the fuses and battery
to make sure that they are still good and that they are properly
inserted.
Replacing The Fuses
1. Disconnect the test leads from the meter and any item under test.
2. Open the fuse door by loosening the screw on the door using a Phillips
head screwdriver.
3. Remove the old fuse from its holder by gently pulling it out.
4. Install the new fuse into the holder.
5. Always use a fuse of the proper size and value (0.5A/1000V fast blow
for the 400mA range, 10A/1000V fast blow for the 10A range).
6. Put the fuse door back in place. Insert the screw and tighten it securely.
For service on this or any other REED product, contact REED Instruments
at [email protected].

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