Extech Instruments 380900 User manual

User Guide
Dual Channel, True RMS MultiMeter
with PC interface
Model 380900

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Introduction
Congratulations on your purchase of the Extech 380900 Dual Channel, Datalogging, True RMS
MultiMeter. This 60,000 count meter features dual input channels with dual display for measuring
two voltages or voltage and current simultaneously. Additional measurements include
Capacitance, Frequency, Resistance, Continuity, Duty Cycle and Diode test. Over 10,000
measurement readings on both channels can be logged by the meter and later transferred to PC
using the RS-232 interface. Real-time meter/PC logging is also supported. This meter is shipped
fully tested and calibrated and, with proper use, will provide years of reliable service.
Safety
International Safety Symbols
This symbol, adjacent to another symbol or terminal, indicates the user must refer to
the manual for further information.
This symbol, adjacent to a terminal, indicates that, under normal use, hazardous
voltages may be present
Double Insulation or Reinforced insulation
OVERVOLTAGE CATEGORY III
This meter meets the IEC 610-1-95 standard for OVERVOLTAGE CATEGORY III. Cat III meters are
protected against overvoltage transients in fixed installation at the distribution level. Examples
include switches in the fixed installation and some equipment for industrial use with permanent
connection to the fixed installation.

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Safety Precautions
1. Improper use of this meter can cause damage, shock, injury or death. Read and understand
this user’s manual before operating the meter.
2. Make sure any covers are properly closed and secured.
3. Always remove the test leads before replacing the battery or fuses.
4. Inspect the condition of the test leads and the meter itself for any damage before operating the
meter. Repair or replace any damage before use.
5. Do not exceed the maximum rated input limits.
6. Use great care when making measurements if the voltages are greater than 25VAC rms or
35VDC. These voltages are considered a shock hazard.
7. Always discharge capacitors and remove power from the device under test before performing
Capacitance, Diode, Resistance or Continuity tests.
8. Remove the battery from the meter if the meter is to be stored for long periods.
9. To avoid electric shock, do not measure AC current on any circuit whose voltage exceeds
1000V AC.
10. Voltage checks on electrical outlets can be difficult and misleading because of the uncertainty
of connection to the electrical contacts. Other means should be used to ensure that the
terminals are not "live".
11. The product is intended only for indoor use
12. If the equipment is used in a manner not specified by the manufacturer, the protection provided
by the equipment may be impaired.
13. Pollution degree: 2
Input Limits
Function Maximum Input
V DC, V AC, Frequency, Duty Cycle 1000V DC/AC
A AC, A DC 20A (30 seconds max)
Resistance, Continuity 1000V DC/AC
Capacitance 1000V DC/AC
Diode test 1000V DC/AC

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Meter Description
1. LCD display
2. Channel 2 value, unit and function
3. Channel 1 value, unit and function
4. ZERO function
5. Frequency function
6. Record function
7. Manual range key
8. Shift key
9. Max/Min/Hold key
10. Channel 1/Channel 2 select key
11. Rotary function selection switch
for Channel 2
12. Rotary function selection switch
for Channel 1
13. Common input jack
14. Channel 1 V/mV/Ω/Cap/Diode/TTL
input jack
15. Channel 2 V/mV/mA/µA input jack
16. 10A input jack
1
4
5
6
9
10
12
13
14
2
3
7
8
11
15
16

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Operation
Measurement Considerations
Notice: Read and understand all WARNING and CAUTION statements listed in the safety section
of this operation manual prior to using this meter.
1. Always move the rotary function switch to the OFF position when the meter is not in use.
2. If "OL" appears on the display during a measurement, the measurement exceeds the range
selected. Change to a higher range.
3. Functions used when the meter is in the dual channel mode may take longer to execute due to
the fact that the meter is multiplexing.
AC/DC Voltage Measurements
1. Insert the black test lead into the negative COM jack and the
red test lead into the Channel 1 or Channel 2 input jack.
2. Set the function switch, for the selected channel, to the
"VAC" "VDC" "mVAC" "mVDC" position.
3. Connect the test leads to the circuit to be measured
4. Read the voltage measurement on the display
AC/DC Current Measurements (Channel 2 only)
Note: When making single channel current measurements, set the Channel 1 rotary switch to the
OFF position.
CAUTION: Do not make 20A current measurements for longer than 30 seconds. Exceeding 30
seconds may cause damage to the meter and/or the test leads.
1. Insert the black test lead into the negative COM jack.
2. For current measurements up to 6000A, set the Channel 2
function switch to the "A" position and insert the red test lead
into the Channel 2 mA-Ajack.
3. For current measurements up to 600mA, set the Channel 2
function switch to the "mA" position and insert the red test lead
into the Channel 2 mA-Ajack.
4. For current measurements up to 10A, set the Channel 2
function switch to the "A" position and insert the red test lead
into the Ajack.
5. Remove power from the circuit under test and open the circuit
at the point where you wish to measure current.
6. 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.
7. Apply power to the circuit.
8. Read the current on the display.

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Resistance and Continuity Measurements (Channel 1 only)
Note: When measuring resistance or continuity, Channel 2 is automatically disabled.
1. Insert the black test lead banana plug into the negative COM
jack and the red test lead banana plug into the Channel 1
V//mV/CAP/ jack.
2. Set the function switch to the "" position.
3. Press the SHIFT key momentarily to select Continuity (if
required).
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. For Resistance tests, read the resistance on the display.
6. For Continuity tests, if the resistance is < 40an audible tone will sound
Capacitance Measurements
Note: When measuring capacitance or diodes, Channel 2 is automatically disabled.
Note: If auto range is selected, the range is 6000 counts. If manual range is selected, the range is
extended to 9999 counts.
1. Insert the black lead into the negative COM jack and the red
test lead into the Channel 1 V//mV/CAP/ jack.
2. Set the function switch to the "CAP " position.
3. Touch the test leads to the capacitor to be tested and read
the measured value.
Frequency and Duty Cycle Measurements
When measuring V, mV, A, mA, or µA, the measurement of
frequency and duty cycle can be displayed.
1. Select either CH1 or CH2 (as indicated by the ▼icon) with
the CH1/CH2 key.
2. Press the Hz key and the frequency will appear in the lower
display and the duty cycle will appear in the upper display for
the channel selected.
3. Press the Hz key again to exit the function.

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TTL Frequency and Duty Cycle Measurements
1. Set the Channel 1 function switch to the mV/TTL
position.
2. Press the SHIFT key momentarily to select the TTL
function.
3. TTL Frequency and Duty Cycle will be displayed
Diode Test
1. Insert the black lead into the negative COM jack and the red
test lead into the positive jack.
2. Set the function switch to "CAP " position.
3. Press the SHIFT key momentarily to select the diode
function.
4. Touch the test probe tips to the diode or semiconductor
junction you wish to test. Note the meter reading.
5. Reverse the test lead polarity by reversing the red and black
leads. Note this reading.
6. The diode or junction can be evaluated as follows:
A. If one reading displays a value and the other reading
displays "OL", the diode is good.
B. If both readings display "OL", the device is open.
C. If both readings are very small or 0, the device is shorted.
Dual Channel Voltage Measurements
Warning: Both channels share the same ground. Voltages with different grounds cannot be
measured.
Note: Functions may take longer to execute when in the dual channel mode.
1. Insert the black test lead into the negative COM
jack and the red test leads into the input jacks for
Channel 1 and Channel 2.
2. Set the Channel 1 voltage function: "VAC",
"VDC", "mVAC", or "mVDC".
3. Set the Channel 2 voltage function: "VAC",
"VDC", "mVAC", or "mVDC”.
4. Connect the test leads in Parallel to the circuit to
be measured.
5. Read the voltage measurements on the display.
V1 V2

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Dual Channel Voltage and Current Measurement
Warning: Both channels share the same ground. Voltage and current with different grounds cannot
be measured.
Note: The COM jack should be used as the CURRENT ground. The Ajack should be used as the
VOLTAGE ground. The two grounds are connected internally by a fuse.
1. Set the Channel 1 voltage function: "VAC", "VDC", "mVAC", or "mVDC".
2. Set the Channel 2 current function: "ACA", "DCA", "ACmA", "DCmA”, “ACµA”, or “DCµA”.
3. Insert the test leads into the input jacks.
4. Connect the test leads in PARALLEL to the voltage circuit to be measured, and connect the
test leads in SERIES with the current to be measured.
5. Read the voltage and current measurements on the display.

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Advanced Functions
MAX, MIN, Hold Function
Note: The meter will exit autoranging and hold the present range when the MAX/MIN/H key is
pressed. Pre-select a different range if required.
This mode is used to “freeze” the display and also to enter the Max/Min recording mode.
1. Press and hold the MAX/MIN/H key until the meter beeps to freeze the LCD display. The 'H'
(Hold) icon will appear on the display.
2. Press a second time and the “MAX” icon will appear with the maximum values recorded since
the HOLD mode was entered.
3. Press a third time and the “MIN” icon will appear with the minimum values recorded since the
HOLD mode was entered.
4. Pressing the key for a single beep will cycle the display through Hold, Maximum and Minimum.
5. Press and hold the key for two beeps to exit the mode.
Relative Mode (ZERO)
The Relative Mode permits the user to store the current measurement as a reference value and
compare the reference value to subsequent readings. In Relative mode, the meter displays: Actual
reading minus the Relative reference value.
Press the "ZERO" key to enter the Relative mode. The triangular Relative icon and ZERO will
appear on the display. The display will read zero indicating that the actual and relative
measurements are the same. As the actual measurement changes, the display will indicate the
difference between actual and reference (zeroed) value. Press and hold the ZERO key for two
beeps to exit the Relative Mode.
Range Hold
Press the RANGE key to enter manual ranging for the channel selected by the ▼icon. When
selected, the meter will lock the present range. Press the RANGE key again to proceed to other
ranges as indicated by the decimal point and units indicators. Press and hold the RANGE key for
two beeps to return to the AUTO Ranging mode.

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Datalogging
The 380900 can store up to 10,708 records for both channels. These records can be transferred to a
PC for storing, viewing and plotting using the RS-232 interface cable and Windows® software
included. Data may also be stored directly into the PC using the software.
Note: If a low battery condition is detected during datalogging, it will stop automatically.
Note: Capacitance, frequency, duty cycle and logic functions cannot be recorded in the datalogging
or data acquisition modes.
Setting the Sampling Time
1. Hold the REC button and turn the power on. The top display will show the sampling rate in
seconds.
2. To change the sampling time, press the RANGE button once to increment the sampling time by
1. The Sampling rate range is 0 to 253 seconds. Note: If the sampling time is set at 0 seconds,
the DMM will record one measurement and stop. For dual channel datalogging, sampling time
should be 2 seconds or greater.
3. To increment the sampling time faster, hold the RANGE button for more than 2 seconds.
4. When approaching the desired sampling time, release the RANGE button and then increment
by 1 to reach the desired rate.
5. Hold the REC button for 2 seconds to return to the DMM function.
Clearing Memory
There are three methods to clear the memory.
1. Hold the REC button and turn the power on. The memory will clear and the top display will
show the sampling rate in seconds.
2. Press the “Clear Data Logger Memory” button in the software datalogger screen.
3. Send a CNTL-C via the rs232 interface.
Start and Stop Datalogging
1. Clear the memory before starting a datalogging session.
2. Press the REC button to start datalogging. The LCD will show an REC symbol.
3. To stop datalogging, press and hold the REC button until the REC symbol goes out.
4. To resume datalogging, press the REC button again. Note: If any function switches are
changed from their original position at the start of datalogging, an ERR will be displayed and
datalogging will not resume.
Note: The Sample Rate should be set to 2 secs or greater for dual channel datalogging.
Windows® Data Acquisition and Datalogging Software
The supplied software is dedicated for use with the Extech Model 380900 Meter. The software displays
data as a Data List or as an X-Y Graph. Data is stored as a text file that can then be opened in
spreadsheet or other software programs Refer to the separate Software User Guide included on the
supplied program CD-ROM for software specific instructions.