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).