ENGLISH
■
MICRO-OHMMETER
6255
User Manual
Statement of Compliance
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
certifies that this instrument has been calibrated using
standards and instruments traceable to international
standards.
We guarantee that at the time of shipping your
instrument has met its published specifications.
An N.I.S.T. traceable certificate may be requested at
the time of purchase, or obtained by returning the
instrument to our repair and calibration facility, for a
nominal charge.
The recommended calibration interval for this
instrument is 12 months and begins on the date of
receipt by the customer. For recalibration, please use
our calibration services. Refer to our repair and
calibration section at www.aemc.com
Serial #:
.
Catalog #: 2129.84
Model #: 6255
Please fill in the appropriate date as indicated:
Date Received:
Date Calibration Due:
Chauvin Arnoux®, Inc.
d.b.a AEMC
®
Instruments
www.aemc.com
2 Micro-Ohmmeter Model 6255
CONTENTS
1. INTRODUCTION ............................................................................................ 4
1.1. Precautions ......................................................................................... 4
1.2. Battery Handling .................................................................................. 5
1.3. Definition of Measurement Categories (CAT) ...................................... 5
1.4. Receiving Your Shipment .................................................................... 6
1.5. Ordering Information ........................................................................... 6
2. FEATURES .................................................................................................... 7
2.1. Description .......................................................................................... 7
2.2. Applications ......................................................................................... 7
2.3. Key Features ....................................................................................... 8
2.4. Control Features .................................................................................. 9
2.5. Button Functions ............................................................................... 10
2.6. Display Symbols ................................................................................ 11
3. SPECIFICATIONS ....................................................................................... 13
3.1. Electrical ............................................................................................ 13
3.2. Mechanical ........................................................................................ 14
3.3. Display............................................................................................... 14
3.4. Environmental ................................................................................... 14
3.5. Safety ................................................................................................ 14
4. OPERATION ................................................................................................ 15
4.1. Quick Summary ................................................................................. 15
4.2. Instrument Configuration (SET-UP Mode) ......................................... 17
4.3. Operating Procedure ......................................................................... 26
4.4. Selecting the Test Range .................................................................. 28
4.5. Measurement Modes ......................................................................... 29
4.6. Ambient Temperature Compensation ................................................ 33
4.7. Activating Alarms ............................................................................... 36
5. MEMORY/PRINTING ................................................................................... 37
5.1. Managing and Printing the Data in Memory ...................................... 37
5.2. Displaying and Printing Stored Measurements .................................. 38
5.3. Cables and Printers Used with the Interface Port .............................. 40
6. DATAVIEW .................................................................................................. 42
7. TROUBLESHOOTING ................................................................................. 43
7.1. Fault Indicators .................................................................................. 43
8. APPLICATION EXAMPLES ........................................................................ 44
8.1. Measuring Winding Resistance of Motors and Transformers ............ 44
8.2. Measuring Resistance on Electric Motors ......................................... 45
8.3. Battery Strap Measurements ............................................................. 45
9. MAINTENANCE ........................................................................................... 46
9.1. Warning ............................................................................................. 46
9.2. Cleaning ............................................................................................ 46
9.3. Charging/Recharging the Batter y ...................................................... 46
9.4. Battery and Fuse Replacement ......................................................... 47
REPAIR AND CALIBRATION ........................................................................... 48
TECHNICAL AND SALES ASSISTANCE ....................................................... 48
LIMITED WARRANTY ...................................................................................... 49
Micro-Ohmmeter Model 6255 3
instructions whenever this danger symbol appears.
In the European Union, this product is subject to a separate collection
accordance with directive WEEE 2002/96/EC
1. INTRODUCTION
Thank you for purchasing the AEMC Micro-Ohmmeter Model 6255. For best
results from your instrument and for your safety, read the enclosed operating
instructions carefully and comply with the precautions for use. These products
must be only used by qualified and trained users.
WARNING, risk of DANGER! The operator must refer to these
CAUTION! Risk of electric shock. The voltage at the parts marked
with this symbol may be dangerous.
Equipment is protected by double insulation.
Battery
Important instructions to read and to fully understand.
Useful information or tip to read.
Compliance with the Low Voltage & Electromagnetic Compatibility
European directives (73/23/CEE & 89/336/CEE)
system for recycling electrical and electronic components In
1.1. Precautions
Refer to the following warnings to ensure personnel safety and proper instrument
operation.
Read the user manual before performing any tests with this instrument .
Only test de-energized circuits. Never connect to a live circuit.
When measuring resistance with a high inductive component
(transformers, motors, etc.), after ending the measurement the
instrument discharges the inductive sample and the warning icon
appears for the entire duration. Never disconnect the connection wires
before this icon disappears.
Do not use the instrument in an explosive environment, including poorly
ventilated battery rooms and enclosures.
Ensure the battery is fully charged prior to testing. If unused for several
months, recharge the battery. (We recommend monthly recharging.)
Use only direct replacements for blown fuses.
Do not use alcohol or oil based cleaner s when cleaning the instrument.
Only use soapy water with a damp cloth or sponge.
Test leads and measuring wires must be in good condition; replace
immediately if there is any deterioration (insulation split, burnt, etc.).
Never exceed the safety values indicated in the specifications.
4 Micro-Ohmmeter Model 6255
1.2. Battery Handling
Your instrument is equipped with a NiMH battery. This technology offers
several advantages:
Long battery charge life for a limited volume and weight.
Possibility of quickly recharging your battery.
Significantly reduced memory effect: you can recharge your battery
even if it is not fully discharged.
Respect for the environment: no pollutant materia ls suc h as lead or
After prolonged storage, the battery may be completely discharged. If so, it
must
battery may take several hours. The instrument cannot be used when the
battery is being recharged.
To maximize battery life:
NiMH technology allows a limited number of charge/discharge cycles
depending significantly on:
See §9 for battery replacement instructions.
cadmium, in compliance with the applicable regulations.
be completely recharged. Full recharging of a completely discharged
At least 5 charge/discharge cycles will be necessary for your battery
to recover 95% of its capacity.
Only charge your instrument at temperatures between 32° and 104°F
(0° and 40°C).
Comply with the conditions of use defined in this user manual.
Comply with the storage conditions specified in this user manual.
The conditions of use.
The charging conditions.
Do not dispose of the battery pack with other solid waste. Used
batteries must be entrusted to a qualified recycling company or to a
company specialized in processing hazardous materials.
1.3. Definition of Measurement Categories (CAT)
CAT IV Measurement category IV corresponds to measurements taken at
the source of low-voltage ins tallations.
Example: power feeders, counters and protection devices.
CAT III Measurement category III corresponds to measurements on
building installations.
Example: distribution panel, circuit-breakers, machines or fixed
industrial devices.
CAT II Measurement category II corresponds to measurements taken on
circuits directly connected to low-voltage installations.
Example: power supply to domestic electrical appliances and
portable tools.
Micro-Ohmmeter Model 6255 5
1.4. Receiving Your Shipment
Upon receiving your shipment, make sure that the contents are consistent
with the packing list. Notify your distributor of any missing items. If the
equipment appears to be damaged, file a claim immediately with the carrier
and notify your distributor at once, giving a detailed description of any
damage. Save the damaged packing container to substantiate your claim.
1.5. Ordering Information
Micro-ohmmeter Model 6255 …..………...........................….... Cat. #2129.84
Includes extra-large tool bag, set of two 10 ft. (3m) Kelvin clips (10A - Hippo),
set of two 10 ft. (3m) Kelvin probes (1A - Spring Loaded), one RS-232 DB9
F/F 6 ft. null modem cable, RS-232 to USB adapter, US 115V power cord,
quick reference guide, NiMH rechargeable 6V battery pack, and USB thumb
drive supplied with user manual and DataView
Replacement Parts:
Kelvin Clips 10 ft. (3m) 10A-Hippo..…….……................…......... Cat. #1017.84
Kelvin Probes 10 ft. (3m) 1A Spring Loaded ….............…......... Cat. #2118.73
Adapter - RS-232 to USB 2.0 Adapter.
Cable - PC RS-232 DB9 F/F 6 ft. (1.8m) Null Modem Cable …. Cat. #2119.45
Replacement Battery 6V, 8.5 Ah rechargeable NiMH ……........ Cat. #2129.91
115V Power Cord ……………………………………….…..…...... Cat. #5000.14
Extra-large classic tool bag ………………….……………..…...... Cat. #2133.73
Fuse, set of 3, 16A/250V, 1 1/4 x 1/4" (6.3x32mm) fast blow … Cat. #2129.98
Fuse, set of 10, 2A/250V, 3/4 x 3/16" (5x20mm) fast blow ….... Cat. #2129.99
Accessories:
Kelvin Clips 20 ft. (6m) 10A-Hippo …............................…......... Cat. #2118.70
Kelvin Probes 20ft (6m) 1A Spring Loaded …............................ Cat. #2118.74
Kelvin Probes Pistol Grip 10 ft. (3m) 10A Spring Loaded …...... Cat. #2118.75
Kelvin Probes Pistol Grip 20 ft. (6m) 10A Spring Loaded …...... Cat. #2118.76
Kelvin Probes 10 ft. (3m) 10A Spring Load ed …........................ Cat. #2118.77
Kelvin Probes 20 ft. (6m) 10A Spring Loaded …........................ Cat. #2118.78
Kelvin Clips 10 ft. (3m) 1-10A …....................................…......... Cat. #2118.79
Kelvin Clips 20 ft. (6m) 1-10A …....................................…......... Cat. #2118.80
RTD temperature probe
RTD temperature probe with 7 ft. (2m) extension cable ............ Cat. #2129.96
Inverter – 12VDC to 120VAC 200 Watt for vehicle use ............. Cat. #2135.43
For the accessories and replacement parts, visit our web site:
www.aemc.com
…............................................…......... Cat. #2129.95
…......................…......... Cat. #5000.60
®
software..
6 Micro-Ohmmeter Model 6255
2. FEATURES
2.1. Description
The Micro-ohmmeter Model 6255 performs low resistan ce m easur eme nts
from 1μΩ
non-inductive resistances with test currents (continuou s or pulsed) from 1mA
to 10A. A built-in thermal switch protects the micro-ohmmeter against
overheating on the 10A range when in continuous use.
The large, easy-to-read liquid crystal display is 2.25 x 4.00". It displays the
value of resistance, metal type, reference and ambient temperatures (if
selected), alarm conditions (if selected), test current and range and test mode
(Resistive, Inductive or Auto). You can perform long measurement campaigns
(up to 60 minutes) at 10A
load charging (measurement stabilization in under 2 seconds).
The Model 6255 employs a four-wire Kelvin configuration, which eliminates
test lead resistance for a measurement accuracy of 0.05%. A built-in circuit
filters out AC signals. The instrument provides laboratory-level performance,
offering a high precision of 0.05% with a maximum resolution of 0.1μΩ over
seven ranges from 5mΩ to 2.5kΩ.
The Model 6255 is packaged in a sealed case. It provide s a rating of IP64 with
cover closed (IP53 with cover open) and locking metal measuring terminals.
The instrument is primarily a field device, but can also be used in a shop or
manufacturing process.
For operator safety and instrument protection, the instrument is fuse protected
at the inputs. Two fuses, accessible behind the front panel, protect against
stored energy in inductive loads. Enh anc ed internal circuitry protects against
possible inductive kickback when the current is shut off.
2.2. Applications
Some of the more popular and most frequent uses of the micro-ohmmeter are
in applications for:
to 2500Ω. Th is easy-to-use instrument measures all inductive or
. Other features include long battery life and fast
DC
Checking metallic coating resistance, especially in aeronautics
Ground connections and continuity measurement
Resistance measurements on motors and transformers
Contact resistance measurements on break ers and sw itche s
Component measurement
Electrical cable resistance measurement
Mechanical bond tests
Wire to terminal connections
Aircraft and rail bonds
Many other very low resistance samples
Micro-Ohmmeter Model 6255 7
2.3. Key Features
Measures from 1µΩ to 2500Ω
Test current selection from 1mA to 10A
RTD temperature measurement (optional)
Automatic or manual temperature compensation
Two programmable alarms with high or low triggering
Stores up to 1500 test results
Selectable Inductive or Resistive test modes
Operator safety by automatic discharge of residual charge on the
equipment under test
Instantaneous, continuous or mult ipl e test oper at ion
Selectable metal type (copper, aluminum or other) for temperature
compensation
Internal, rechargeable batteries conduct up to 5000 tests at 10A
A built-in battery pack recharger recharges the batteries by
connecting to the AC line (90V/264V, 45Hz/420Hz) using a standard
line cord
4-Wire measurement with automatic compensation of undesirable
voltages and lead resistance
Large multi-function backlit dis play
Direct display of the measurement with its unit s, range ,
measurement mode, and (if activated) temperature compensation.
Measurement can be initiated from the front panel or remotely
through the 9-pin communication port
Rugged, sealed case
8 Micro-Ohmmeter Model 6255
2.4. Control Features
Figure 2-1
1. Kelvin input terminals
2. AC line recharging receptacle
3. Large multi-line backlit liquid crystal display
4. RTD temperature input
5. Communication / remote operation port
6. Range selection switch
7. Test, Start/Stop button
8. Eight program / function buttons
Micro-Ohmmeter Model 6255 9
2.5. Button Functions
R ( )
In SET-UP mode, selects a function or increments a flashing
parameter.
In SET-UP mode, selects a function or decrements a flashing
parameter
In SET-UP mode, accesses the func tion to be modified.
In Wrap-Around mode, selects the parameter to be modified
(from left to right)
In SET-UP mode, shifts the decimal point and selects the unit.
2nd
PRINT
PRINT
MEM
R ( )
ALARM
METAL
MEM
MR
Activates the secondary function of a button. The symbol
appears on the left side of the display.
Immediate printing of the measurement to a serial printer. If the
temperature compensation function has been activated, the
calculated result and the temperatures involved are also
printed.
Retrieves stored data for printing (this function is independent
of the setting of the switch) except in the OFF and SET-UP
positions.
Activates or deactivates the temperature compensation
function to calculate the resistance measured at a temperature
other than ambient measurement temperature.
Activates or deactivates the alarms. High or low triggering
values are adjusted in SET-UP.
Selects the desired measurement mode prior to starting one of
the following measurements: Inductive mode (continuous
test), non-inductive mode (instantaneous test) or non-inductive
mode with automatic triggering (multiple tests).
Selects the metal type for the temperature compensation
calculation: Cu, Al, or Other metal.
Stores the measurement at an address identif ied by an objec t
number (OBJ) and a test number (TEST).
Two presses on this button are required, one to select the
location (use the ▲ and ► buttons to change the location) and
another to store the measurement.
Retrieves stored data (this function is independent of the
selector setting of the switch) except for the OFF and SETUP positions. Data is viewed using the ▲ and ► buttons.
The
Turns the display backlight ON or OFF.
, , and ALARM buttons can be used.
Activates or deactivates the buzzer and adjusts the sound
level.
10 Micro-Ohmmeter Model 6255
2.6. Display Symbols
Cu
The display incorporates two lines of characters to display test results, as well as
a library of symbols to assist the operator in determining conditions at a glance.
The symbols that can appear are shown in Figure 2-2 and are descri bed bel ow.
Figure 2-2
Buzzer ON.
Battery condition
R ( )
Al
Other metal
Temperature compensation ON
Copper metal type selected
Aluminum metal type selected
User defined metal type selected
Communication port active
ALARM 1
ALARM 1
ALARM 2
ALARM 2
OBJ.
TEST
°C / °F
PRINT
MEM
REMOTE
MR
Alarm 1 active with high set point
Alarm 1 active with low set point
Alarm 2 active with high set point
Alarm 2 active with low set point
First position locator for data stored in memory
Second position locator for data stored in memory
Temperature displayed in either degrees Centigrade or
Fahrenheit
Printing current test result or tests stored in memory
Displayed measurement about to be stored in memory
Instrument under computer control
Memory recall
Micro-Ohmmeter Model 6255 11
mV m
Ω
Units of measure
AUTO
ST BY
OPER
250Ω 10mA
2500mΩ 1A
250mΩ 10A
5mΩ 10A
2500Ω 1mA
25Ω 100mA
25mΩ 10A
Memory utilization indicator
Resistive material test mode selected
Inductive material test mode select ed
Repetitive test mode selected
System idle ready to start a test
Test in process
Second function of a button activated
CAUTION! Refer to the user manual before using the
instrument.
2500 ohm, 1 milliamp test range selected
250 ohm, 10 milliamp test range selected
25 ohm, 100 milliamp test range selected
2500 milliohm, 1 Amp test range selected
250 milliohm, 10 Amp test range selected
25 milliohm, 10 Amp test range selected
5 milliohm, 10 Amp test range selected
12 Micro-Ohmmeter Model 6255
Accuracy over 1 year
(23°C ± 5°C)
5mΩ
0.1µΩ
0.15% ± 1.0µΩ
10A
50mV
25mΩ
1µΩ
0.05% ± 3µΩ
10A
250mV
250mΩ
10µΩ
0.05% ± 30µΩ
10A
2500mV
2500mΩ
0.1mΩ
0.05% ± 0.3mΩ
1A
2500mV
25Ω
1mΩ
0.05% ± 3mΩ
100mA
2500mV
250Ω
10mΩ
0.05% ± 30mΩ
10mA
2500mV
2500Ω
100mΩ
0.05% ± 300mΩ
1mA
2500mV
3. SPECIFICATIONS
3.1. Electrical
Specifications are given for an ambient temperature of 73°F ± 9°F (23°C ± 5°),
relative humidity of 45 to 75% and a supply voltage of 6V ± 0.1V.
All specifications are subject to change without notice.
Measurement Method:
4-Wire Kel v in resistance measurement with compensation for stray/residual
voltages.
Measurement Ranges:
Range Resolution
73°F ± 9°F
Measurement
Current
Voltage Drop
Temperature Measurement: 3-wire 100Ω Platinum RTD
Accuracy: ± 0.5°C
Resolution: 0.1°C
Influence From Environment Conditions:
Temperature: 0.1% per 10°C typical, 0.25% max
Humidity: 0.5% max from 10 to 90%
Battery Voltage: ± 0.1% from 4.5 to 7.5V
Open Circuit Voltage: 7V
Operating Voltage: 5 to 6V
Power Source:
Rechargeable 6V, 8.5 Ah NiMH battery pack, built-in 90 to 256V (45 to
420Hz) charger
Battery Life: 5000 10A tests (typical)
Battery Charging: 120/240V
Auto-Pow er Off: when battery voltage <5.0V
Micro-Ohmmeter Model 6255 13
max
DC
DC
± 20% (45 to 400Hz) line voltage
AC
Low Battery Indication: The symbol is displayed when the battery needs
to be recharged
Overload Input Protection: 250Vrms
Fuses:
F1 - 1 1/4 x 1/4" (6.3 x 32mm), fast acting, 16A/250V current source protection
F2 - 3/4 x 3/16" (5 x 20mm), fast acting, 2A/250V charging circuit protection
3.2. Mechanical
Dimensions: 10.63 x 9.84 x 7.09" (270 x 250 x 180mm)
Weight: 8.1 lbs (approximately 3.69kg) without leads
Case Protection: ABS plastic polycarbonate: watertight to IP64 (cover closed),
water resistant to IP53 (cover open)
Color: Safety yellow case with gray faceplate
3.3. Display
Blue Electroluminescent backlit Liquid Crystal Display (LCD), 2.25 x 4.00" (57.2 x
102mm) with icons and two numeric fields for data presentation.
One numeric field contains 4 digits for displaying ambient and reference
temperature levels on the top line in “temperature compensation” mode. The
other contains 5 digits and is used to display the measured values on the bottom
line. Error messages are also listed on the bottom line.
3.4. Environmental
Operating Temperature:
14° to 132°F (-10° to 55°C), 10 to 80% (non-condensing)
Storage Temperature: -40° to 140°F (-40° to 60°C)
3.5. Safety
EN 61010-1, 50V, CAT III, Pollution Degree 2
Conducted and radiated emission:
EN 55022, class B
EN 61000-3-2
EN 61000-3-3
Immunity:
EN 61000-4-2 electrostatic discharges
EN 61000-4-3 radiated fields
EN 61000-4-5 shock
EN 61000-4-6 conducted disturbanc es
EN 61000-4-11 voltage drops
EN 61000-4-4 bursts
14 Micro-Ohmmeter Model 6255
4. OPERATION
Fully charge the instrument battery before use.
4.1. Quick Summary
The following is a summary instruction set that will assist the operator in
performing measurements. For complete details on each function and test
method refer to the operating procedure section (§ 4.3) and instrument
configuration section (§ 4.2) in this manual.
WARNING: Read and follow all safety warnings on page 4 before
operating this instrument.
1. Turn the instrument on and select a test range by turning the rotary
switch to the desired position. If the resistance of the device under test
is unknown, start with the highest range (2500Ω) and work down to
increase resolution as necessary.
2. Select the test method best suited for the measurement by pressing the
button to select inductive (continuous test), resistive
(instantaneous test) or AUTO (multiple testing).
3. Activate the backlight, if necessary, by pressing the button.
4. Activate the buzzer, if desired, by pressing yellow
the button.
5. Activate alarms, if desired, by pressing the yellow 2nd button followed by
the ALARM button. Successive presses of this two-button sequence will
select Alarm 1, Alarm 2 or both.
6. Select the metal type for the device under test by pressing the yellow
nd
2
button followed by the METAL button. Successive presses of this
two-button sequence will select Copper (Cu), Aluminum (Al) or Other
metal. This will be needed for temperature compensation.
7. Activate temperature compensation by pressing the R ( )
reference temperature will appear followed by the ambient temperature
on the top line of the display.
nd
2
button followed by
button. The
Micro-Ohmmeter Model 6255 15
8. Start the test by pressing the START/STOP button. The resistance
reading will appear on the lower line of the display. The symbol OPER
will appear on the lower left to indicate that a test is in process. The
Stand-by symbol ST BY will appear when the test is completed.
Resistive element tests will stop automatically. Inductive and AUTO
testing will stop when you push the START/ STOP button a second
time.
9. Store the test result in memory by pressing the MEM button at the
conclusion of a test. The next available location will be presented on the
top line of the display. To use this location, press the MEM button a
second time.
10. Recall readings from memory by pressing the yellow
by the MEM button. The last measurement stored in location OBJ: X
TEST: X will be displayed.
Use the ▲, ▼ and ► buttons to select the object and test memory
location to review. All information from the measurement is availabl e for
review including metal type, ambient and reference temperatures,
resistance at ambient and reference temperatures, test range and test
current.
nd
2
button followed
Typical Operational Display
Figure 4-1
16 Micro-Ohmmeter Model 6255
4.2. Instrument Configuration (SET-UP Mode)
4.2.1. Program Menu Tree
The menu tree below shows the order in which functions appear in the Menu and
sub-menus of set up mode.
Set
r5 – OFF – Trig – PC – uT100 – Print
buzz – off – low high
EdSn – displays internal serial number
EdPP – displays firmware number
Lang – Lg Gb – Lg F
trEF – value
tAnb – Prb – nPrb
nEtA – Copper alpha – Aluminum alpha, Other Metal
ALPH – value
dEg – dEgF – dEgC
ALAr – Alarm 1 – Alarm 2
LlgH – t=OFF – t=1 – t=5 – t=10
nEn – dEL – dEL O – Y – n
The cursor buttons ▲, ▼ and ► have the following functions in the SET-UP
menu:
The up Arrow ▲ button selects the next function to be programmed in
the top level menu and increments the value of the flashing variable in
the sub-menus.
The down Arrow ▼ button selects the previous function to be
programmed in the top level menu and decrements the value of the
flashing variable in the sub-menus.
The right arrow ► button selects the function displayed in the top level
menu and moves the cursor one place to the right or validates the
programming in the sub-menus. See Cables and Printer Used with the
Interface Port (§5.3) for proper connections.
Micro-Ohmmeter Model 6255 17
4.2.2. Programming the 9-Pin Interface Port (rS)
The 9-pin interface port on the top right side of the front panel can be
programmed to any of five communication methods. These consist of:
Off: Disable input and output functions of the interfac e por t. T his save s
battery power.
Trigger: Enables the remote measurement function.
PC: Activates an RS-232 link between a computer and the unit for
configuring the Model 6255 and for conducting tests and storing results.
When activated, the icon will appear on the display.
VT100: Activates an RS-232 link between a display terminal and the
Model 6255. When activated, the icon will appear on the display.
Print: Activates the RS-232 link between a printer and the Model 6255
for direct printing of test results. When activated, the icon will
appear on the display.
The RS-232 modes also allow programming of transmission speed. The baud
rate choices are: 4800, 9600, 19200 and 31250.
The required data configuration settings are: 8 bits, no parity, 1 stop bit,
hardware control (CTS).
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “rS” appears on the top line of the display.
3. Press the ► button, OFF will appear in the disp lay .
4. Press the ► button to accept this setting or press the ▲ button to scroll
through the other choices of trigger (trlG), PC, Terminal (ut100) and
Print.
5. The choices of PC, terminal and print also require a baud rate selection.
6. After selecting PC, ut100 or Print, pressing the ► button will enter the
baud rate selection menu.
7. Press the ▲ button to toggle the choices for 4800, 9600, 19200 and
31250. When the desired baud rate is in the display, validate it by
pressing the ► button to return to the top level rS menu. The icon
will appear in the display.
8. Proceed to the next programming variable by pressing the ▲ button.
18 Micro-Ohmmeter Model 6255
4.2.3. Setting the Buzzer Level (bUZZ)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “bUZZ” appears on the top line of the display.
3. Press the ► button to scroll through the choices of OFF (no icon
displayed), LOW (small buzzer icon displayed) or HIGH (large
buzzer icon displayed). Each choice will display the
corresponding icon in the top left corner of the display along with the
associated audible sound.
4. When the desired sound level is displayed, press the ► button to
accept it and return to the top level of buzzer set-up.
5. To proceed to the next programming variable, press the ▲ button.
4.2.4. Reading the Internal Serial Number (EdSn)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “EdSn” appears on the top line of the display.
3. Press the ► button to scroll through the serial number. There are 10
digits in the serial number. The first press will display the first five digits.
The second press will display the second five digits.
EXAMPLE: First press displays: t0302
Second press displays: 044-0
Third press displays: 0001 A
4. Press the ► button again to return to the top level of the Serial Number
set-up menu.
5. To proceed to the next programming variable, press the ▲ button.
4.2.5. Reading the Internal Software Version (EdPP)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “EdPP” appears on the top line of the display.
3. Press the ► button to display the firmware version.
4. Press the ► button again to return to the top level of the Software
Version set-up menu.
5. To proceed to the next programming variable, press the ▲ button.
Micro-Ohmmeter Model 6255 19
4.2.6. Setting the Language used for Printing Reports (LAnG)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “LAnG” appears on the top line of the display.
3. Press the ► button to enter the language selection sub-menu.
4. Next, press the ▲ button to toggle between English (Lg Gb) or French
(Lg F).
5. Press the ► button to validate the selection and return to the top level
of the Language set-up menu.
6. To proceed to the next programming variable, press the ▲ button.
4.2.7. Setting the Value for the Reference Temperature (trEF)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “trEF” appears on the top line of the display.
3. Press the ► button to enter the reference temper ature su b-menu. The
current reference temperature will be displayed with the leading digit
flashing.
4. Use the ▲ button to change the leading digit. The minus (-) symbol can
also be programmed in this location.
5. When the desired value is reached, press the ► button to move the
next digit to the right.
6. Use the ▲ button to change this digit, then press the ► button to again
move to the next digit to the right.
7. Repeat this process for each of the 5 digit locations.
8. After the 5th digit is programmed, press the ► button again to return to
the top level of the Reference Temperature set-up menu.
9. To proceed to the next programming variable, press the ▲ button.
The program limits for the reference temperature are 32.0 to
130.0°F and -10.0 to 130.0°C. Attempting to set values outside
these limits will cause error message “Err23” (Entry Out of Range)
to appear in the display.
20 Micro-Ohmmeter Model 6255
4.2.8. Selecting Method and Value for Ambient Temperature (tAnb)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “tAnb” appears on the top line of the display.
3. Press the ► button to enter the ambient temperature sub-menu.
4. The first choice here is to decide if ambient temperature will be
measured using the RTD temperature probe accessory or if it will be
programmed using the same method as described for reference
temperature. “Prb” (measure the ambient temperature using the RTD
probe accessory) or “nPrb” (no probe, manually enter the ambient
temperature) will be displayed, press the ▲ but ton to toggl e bet w een
the two choices.
5. If measuring the ambient temperature is desired, press the ► button
when “Prb” is in the display. The lower display will momentarily show
dashes “-----” and then return to the top level ambient temperature
menu.
6. If manually entering the ambient temperature is desired, press the ►
button when “nPrb” is in the display. The ambient temperature may now
be manually entered.
7. The current programmed ambient temperature will be displayed with the
leading digit flashing.
8. Use the ▲ button to change the leading digit. The minus (-) symbol can
also be programmed in this location.
9. When the desired value is reached, press the ► button to move the
next digit to the right.
10. Use the ▲ button to change this digit then press the ► button to again
move to the next digit to the right.
11. Repeat this process for each of the 5 digit locations.
12. After the 5th digit is programmed, press the ► button again to return to
the top level of the ambient temperature set-up menu.
13. To proceed to the next programming variable, press the ▲ button.
The program limits for the reference temperature are 32.0 to
130.0°F and -10.0 to 130.0°C. Attempting to set values outside
these limits will cause error message “Err23” (Entry Out of Range)
to appear in the display.
Micro-Ohmmeter Model 6255 21
4.2.9. Selecting the Metal Type (nEtA)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “nEtA” appears on the top line of the display.
3. Press the ► button to toggle through the choices of Copper (Cu),
Aluminum (Al) or Other Metal. With each press of the right arrow button,
the metal type icon appears at the top of the display. “nEtA” appears on
the small display and the five digit alpha value appears on the large
display and then automatically returns to the top level of the metal setup menu.
4. To proceed to the next programming variable, press the ▲ button.
4.2.10. Programming the Alpha Value (ALPH)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “ALPH” appears on the top line of the display.
3. Press the ► button to begin programming the alpha value. See Table 2
in §4.6 for common alpha values.
4. The current alpha value will be displayed with the leading digit flashi ng.
5. Use the ▲ button to change the leading digit. When the desired value is
reached, press the ► button to move the next digit to the right.
6. Use the ▲ button to change this digit, then press the ► button to again
move to the next digit to the right.
7. Repeat this process for each of the 5 digit locations.
8. After the 5th digit is programmed, press the ► button again to return to
the top level of the alpha set up menu.
9. To proceed to the next programming variable, press the ▲ button.
4.2.11. Selecting Temperature Units (dEg)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “dEg” appears on the top line of the display.
3. Press the ► button to enter the degree units sub-menu.
4. Use the ▲ button to toggle through the choices of Fahrenheit (dEgF) or
Centigrade (dEgC).
5. Press the ► button to validate the selection and return to the top level
of the Temperature units set-up menu.
6. To proceed to the next programming variable, press the ▲ button.
22 Micro-Ohmmeter Model 6255
4.2.12. Setting Alarm Set Point, Direction and Buzzer Level (ALAr)
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “ALAr” appears on the top line of the display.
3. Press the ► button, Alarm 1 and its set point, direction and buzzer level
will appear with ALARM 1 flashing.
4. To modify the settings of Alarm 1, press the ► button. The direction
arrow will now be flashing. To modify Alarm 2 press the ▲ button,
ALARM 2 will then be flashing.
5. When the direction arrow is flashing, it may be changed by pressing the
▲ button to toggle between HIGH (▲ activates above set point) and
LOW (▼ activates below set point).
6. Press the ► button to adjust the buzzer level for this alarm. The buzzer
icon will be flashing. The choices are OFF (no icon displayed),
LOW (small buzzer icon displayed) or HIGH (large buzzer icon
displayed). The selection is made by pressing the ▲ button while
the icon is flashing.
7. Program the set point value used to trigger the alarm (ignoring the
decimal point) by pressing the ► button. The leading digit will be
flashing. Adjust the digit value using the ▲ button then press the ►
button to move to the next digit to the right.
8. Repeat the process for each of the five digits.
9. Press the ► button when the numeric value is set to the desired
number. The decimal point and units (mΩ or Ω) will be flashing.
10. Set the desired resolution and units by pressing the ▲ button. Each
press will move the decimal point one place to the right. Cycling through
milliohms and then through ohms.
11. To accept the alarm settings once the decimal point and units are at the
desired values, press the ► button. This will bring you to Alarm 2.
Repeat the process as necessary to set Alarm 2’s conditions.
12. When Alarm 2 is set press the ► button to return to the top level of the
alarm programming menu. “ALAr” will again appear on the top line and
the bottom line will be blank.
13. To proceed to the next programming variable, press the ▲ button.
Micro-Ohmmeter Model 6255 23
4.2.13. Setting the Display Timeout (LlgH)
This setting determines the length of time that the backlight will stay on after the
last button press. The choices are OFF (function disabled, backlight stays on
continuously when activated), 1, 5 or 10 minutes.
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “LlgH” appears on the top line of the display.
3. Press the ► button. The last programmed value will appear in the
display.
4. Press the ▲ button to toggle through the choices of OFF, t=1, t=5 and
t=10.
5. When the desired length of time is in the display, press the ► button to
validate the selection.
6. To proceed to the next programming variable, press the ▲ button.
4.2.14. Clearing the Memory (nEn)
You can choose to clear the entire memory or the contents of a specific object.
1. Turn the rotary switch to the SET-UP position.
2. Press the ▲ button until “nEn” appears on the top line of the display.
3. Press the ► button. “dEL” will appear on the lower line of the display.
4. Toggle between clearing the entire memory (dEL) or a specific object
(dEL O) using the ▲ button.
5. To clear a specific object, press the ► button when “dEL. O” is in the
display. The top line will display Obj 01 with the “0” flashing. Use the
arrow buttons to select the object to be deleted.
6. The lower display will show “dEL.02” for example if object number 2 is
selected for deletion. As you press the ▲ button, the selected object will
increment accordingly.
7. Delete the selected object by first pressing the ► button and toggling
between Yes “dEL. Y” or No “dEL. n”
24 Micro-Ohmmeter Model 6255
8. Pressing the ► button while “dEL. Y” is in the display will delete the
contents of the selected object. The display will momentarily display
dashes “-----” and then return to display the next highest object location.
9. Pressing the ► button while “dEL. n” is in the display will cancel the
request.
10. Repeat this process for each object to be deleted.
11. To clear the entire memory contents, turn the rotary switch to the SETUP position.
12. Press the ▲ button until “nEn” appears on the top line of the display.
13. Press the ► button, “dEL” will appear on the lower line of the display.
14. Delete all data from memory by first pressing the ► button, then
toggling between Yes “dEL. Y” or No “dEL. n”
15. Pressing the ► button while “dEL. Y” is in the display will clear all
memory of stored measurements.
16. Pressing the ► button while “dEL. n” is in the display will cancel the
request.
Only objects with data stored in them can be accessed.
To return to the beginning of the SET-UP menu, press the ▲ button when “nEn”
is on the top line of the display.
Micro-Ohmmeter Model 6255 25
4.3. Operating Procedure
WARNING: Before performing the resistance test, verify that the
sample under test is not energized.
4.3.1. Connections and Readings
Clean all surfaces before connecting test leads. Verify a solid connection
between test leads and the sample. Set the range selector switch to the desired
range for the test. If the anticipated resi sta nce is not know n, begin w ith the
highest range (2500Ω) and successively lower the range selection until adequate
resolution is achieved. The START/STOP button will need to be pressed each
time you change ranges. The range selection may be changed while the
instrument is on.
A diagram of the measurement system is shown in Figure 4-2. The Model 6255
generates a current (I) from the internal voltage source (V). A voltmeter
measures the voltage drop V
to be measured (R
the formula R
) and displays the resistance measurement (Rx) directly using
x
= Vx / I.
x
The result is not affected by the other resist an ces en coun tered in the current loop
, Rf, Rc), as long as the total voltage drop induced across Rx remains below
(R
i
the voltage supplied by the source which is between 5 to 6V. The maximum
admissible lead resistance level is R
helps, as they eliminate the effect of the lead resistance (Rf).
at the Kelvin probe contact points to the resistance
x
≈ (V- Vx) / I. The use of Kelvin probes
f
Figure 4-2
R
= Unit internal resistance Rc = Contact resistance
i
R
= Lead resistance Rx = Resistance to be measured
f
26 Micro-Ohmmeter Model 6255
4.3.2. Test Lead Connection
The measurement leads are connected using the four binding posts on the left
side of the front panel as shown in Figure 4-3.
Connect the two red leads to terminals C1 and P1. Connect the two black leads
to terminals C2 and P2.
Any drop in the voltage on the load terminals is measured between the two
“voltage” (V) leads, P1 and P2. The current leads (C1 and C2) can deliver current
from 1mA to 10A.
4.3.3. Very Low Resistance
When measuring very low resistive values in the µΩ range, the presence of stray
DC currents may affect the accuracy of the measurements. These currents can
be present due to a variety of reasons including chemical or thermal EMF in
samples made of dissimilar metals. These EMFs are automatically compensated
for during the measurement process.
The presence of AC interference in the sample under test may cause the
measured value on the display to fluctuate. This interference may become more
noticeable in the presence of strong electric fields. The effects of this interference
may be reduced by twisting the leads around each other.
4.3.4. Meter Readings
When testing resistive samples, the meter reading will stabilize within the first few
hundred milliseconds. On inductive loads (e.g. transformers), the measurement
reading may take from several seconds to a few minutes to stabilize and
depends greatly on the type of equipment and the impedance of the equipment
under test. On very large samples such as utility transformers, 10 to 15 minutes
charging time may be necessary.
Micro-Ohmmeter Model 6255 27
4.3.5. Stand-by (ST BY) State
2500Ω
1mA
100mΩ
250Ω
10mA
10mΩ
25Ω
100mA
1mΩ
2500mΩ
1A
0.1mΩ
250mΩ
10A
10µΩ
25mΩ
10A
1µΩ
5mΩ
10A
0.1µΩ
This is the position that the Model 6255 returns to at the end of a measurement
cycle after:
the operator presses the START/STOP button during a test
any changes to the position of the rotary switch
every low inductive mode measurement
an error is detected
4.4. Selecting the Test Range
The Model 6255 has seven test ranges to choose from. Table 1 lists the
maximum resistance, test current and resolution for each range.
Resistance Range Test Current Resolution
Turn the rotary switch to the desired range, the range and test current will appear
on the lower left side of the display.
The Model 6255 is now ready to start a test.
Table 1
Figure 4-4
28 Micro-Ohmmeter Model 6255
4.5. Measurement Modes
For descriptions of all Fault Indicator (Error) codes, refer to § 7,
Troubleshooting.
4.5.1. Measurement Safety Warnings
WARNINGS:
Never use test leads or measuring wires if there is any evidence of
deterioration (insulation sp lit, b urnt , etc.).
Never exceed the safety values indicated in the specifications.
Never connect the unit to a live circuit.
When the unit is measuring resistance showing a high induc tive
component (transformers, mot ors, etc.) aft er end ing the
measurement (with the measurement current cut-off), the uni t then
discharges this inductance and displays the icon for this entire
duration.
Never disconnect the connection wires before the icon
disappears.
4.5.2. Inductive Resistance Measurement Mode ( )
This mode is intended for performing measurements on inductive devices. Press
the button until the icon show s on the display .
From the Stand-by state, start a test by performing the following:
1. Connect the Kelvin probes to the test specimen.
2. Press the START/STOP button.
3. If the Kelvin probes are incorrectly connected, the display will show
error message “Err 11” (current leads incorrectly connected), or “Err 12”
(voltage leads incorrectly conn ecte d). T he instrument will then return to
the Stand-by state. When the error is correc ted, the t est automatically
begins again.
4. With the current switched off, the residual voltage (V
resistor terminals is measured and displayed. If this voltage level is too
high, “Err 13” will be displayed.
5. The current (I) is switched on at the start of a measurement and
remains on continuously until the unit is manually returned to the Standby state by pressing the START/STOP button.
6. The voltage across the resistor terminals (V
measurement R = (V1 - V0) / I is disp layed.
7. All subsequent measurements comprise only a Vn measurement as V0
remains in memory. The timing sequence for measurement is shown in
Figure 4-5.
) is measured and the
1
) across the
0
Micro-Ohmmeter Model 6255 29
After ending the measurement, with the current turned off, the
Model 6255 will discharge the device under test as long as the test
leads are connected to the device.
Figure 4-5
C = connection check
0 = residual voltage measurement (stored)
1,2,3…n = successive voltage measurements across the resistor terminals
8. The test is stopped by pressing the START/STOP button.
9. Store the measurement by first pressing the MEM button, then select
the object and test location to store the measurement using the arrow
buttons. When the desired location has been selected, press the MEM
button a second time to complete the data storage process.
4.5.3. Resistance Measurement Mode ( )
This mode is intended for measuring contact and metal plating resistance levels.
As a general rule, any resistance level on material with a time constant that is
less than a few milliseconds.
In this mode, only one measurement is performed per cycle. When the
START/STOP button is pressed, the test current is applied for approximately 400
milliseconds. Residual voltage is measured, a resistance measurement is taken
and the test stops automatically.
The advantages of the resistance mode include:
Reduced power consumption as the test current is off between
measurements.
Less heating of the measured resistance.
Improved compensation of stray voltages as these are measured and
compensated before each resistan ce measur e men t.
Press the button until the icon shows on the display.
30 Micro-Ohmmeter Model 6255
From the Stand-by state, start a test by performing the following:
1. Connect the Kelvin probes to the test specimen.
2. Press the START/STOP button.
3. If the Kelvin probes are incorrectly connected, the display will show
error message “Err 11” (current leads incorrectly connected), or “Err 12”
(voltage leads incorrectly connected). The unit will then return to the
Stand-by state. When the error is corrected, the test can begin again by
pressing the START/STOP button.
4. With the current switched off, the residual voltage (V0) across the
resistor terminals is measured. If this voltage level is too high, the unit
displays “Err 13” and returns to Stand-by position. (Refer to § 7 for all
error message descriptions.)
5. The current (I) is switched on when the START/STOP button is
pressed.
6. The voltage across the resistor terminals (V
) is measured and then the
1
current is removed.
7. The measurement resistance result R = (V1 - V0) / I is displayed or error
message “Err 07” is displayed, if an over range condition occurs.
The Model 6255 then returns to the Stand-by state at the end of the
measurement. The instrument is ready to perform another measurement.
Figure 4-6
C = connection check
0 = residual voltage measurement
M = measurement of the voltage across the resistor terminals.
8. Store the measurement by first pressing the MEM button, then select
the object and test location to store the measurement using the arrow
buttons. When the desired location has been selected, press the MEM
button a second time to complete the data storage process.
Micro-Ohmmeter Model 6255 31
4.5.4. Low Inductive Resistance Automatic Triggering Measurement Mode
This mode is intended only for measuring resistance on material without a time
constant (non-inductive). The use of the spring loaded Kelvin probes (Cat.
#2118.77 or Cat. #2118.78) listed in the Accessories sectio n is recommended for
this mode.
From the Stand-by state, start a test by performing the following:
1. Press the button until the AUTO icon shows on the display.
2. Press the START/STOP button.
3. Connect the probes to the specimen. The unit waits until it detects that
the current and voltage leads are connected correctly.
4. Residual voltage (V
) measurement across the resistor terminals is
0
measured.
5. The measurement current (I) is established, the voltage across the
resistor terminals (V
result R = (V
1
) is measured and the measurement resistance
1
- V0) / I is displayed.
6. To start a new measurement cycle, Release at least one probe, and
then reconnect it to the next point or specimen.
If the range is exceeded, the instrument displays “Err 07”. Changing
the range switch position will stop the test cycle and return to the
Stand-by state. Each measurement taken during the test cycle can
be temperature compensated and stored while the test cycle is
running.
7. Store the measurement of each specimen or point by first pressing the
MEM button, then select the object and test location to store the
measurement using the arrow buttons. When the desired location has
been selected, press the MEM button a second time to complete the
data storage process.
8. The test is stopped by pressing the START/STOP button.
32 Micro-Ohmmeter Model 6255
4.6. Ambient Temperature Compensation
The metals used in the windings of certain devices (for example, the copper wire
used in transformer or motor windings) have high temper at ur e coef fi cie nts in the
order of 0.4%/°C (for copper or aluminum). This results in resistance
measurements that are highly dependent on the temperature of the device.
Activating temperature compensation will correct for this condition.
The Temperature Compensation function can be accessed by pressing the R ( )
button before the start of a test in Resistance and Inductive resistance
measurement mode. It can also be activated at any time during Auto
measurement mode.
Its purpose is to compensate the measured or resistance value at the ambient
temperature (whether measured or programmed), to the resistance value that it
should have at a reference temperature.
The compensated resistance level is expressed as follows:
) = R(T
R(T
ref
Where:
) = the resistance value measured at ambient te mpera t ur e
R(T
amb
T
= the temperature measured by a Pt100 probe or programmed by the
amb
operator
alpha = the temperature coefficient of the chosen metal (Aluminum, Copper,
“Other metal”)
T
= the programmed reference temperature to which the measurement is
ref
compensated to
The Temperature Coefficient of copper (near room temperature) is +0.393
percent per degree C. This means if the temperature increases 1°C the
resistance will increase 0.393%.
Example: You have 100 feet of 20 gage wire and its res ist ance is 1.015Ω at
20°C (room temp). If the temperature of the wire goes up 10°C the resistance
will change by 0.0399Ω (10° * 0.00393 / ° * 1.015Ω = 0.0399Ω).
The wire resistance will now be 1.015Ω + 0.0399Ω= 1.0549Ω.
The following table provides the temperature coefficients of the more common
metals and alloys.
The alpha values for copper and aluminum are pre-programmed into the Model
6255. Others may be programmed by selecting Other Metals and then
programming in the alpha constant from the table or other sources.
) * (1 + alpha * T
amb
1 + (alpha * T
amb
)
)
ref
Micro-Ohmmeter Model 6255 33
Material Element/Alloy “alpha” per °C x 10-3
Aluminum Element 4.030
Copper Element 3.930
Nickel Element 5.866
Iron Element 5.671
Molybdenum Element 4.579
Tungsten Element 4.403
Silver Element 3.819
Platinum Element 3.729
Gold Element 3.715
Zinc Element 0.847
Steel Alloy 3.000
Nichrome Alloy 0.170
Nichrome V Alloy 0.130
Table 2
A 100Ω platinum RTD can be connected to the front panel of the Model 6255 to
perform compensated measurements. The temperature sensor and extension
cable assembly, listed in the Accessories section, are recommended. The three
pin temperature compensation port is located to the left of the interface port and
is configured as shown in Figure 4-7
Pt100 connector
Figure 4-7
To measure the ambient air temperature at the Model 6255, plug the optional
temperature sensor directly into the temperature port on the front panel as shown
in Figure 4-8.
34 Micro-Ohmmeter Model 6255
Figure 4-8
To measure the ambient temperature at the specimen, plug the optional
temperature sensor onto the extension cable and plug the extension cable into
the temperature port on the front panel as shown in Figure 4-9.
Figure 4-9
Place the temperature sensor in contact with the specimen or in close proximity
to it. Allow 2 minutes for the sensor to normalize to the specimen temperature
before starting a temperature compensated measurement.
Micro-Ohmmeter Model 6255 35
4.6.1. Activating the Compensation Function
Check to ensure that all desired programming and connections are made
correctly. See Setting the Value for Reference Temperature (§4.2.7) and
Selecting the Method for Ambient Temperature (§4.2.8).
1. Select the range and the measurement mode.
2. Press the R ( ) button. The following information will be displayed onscreen:
R ( )
Metal type selected (Cu, Al or Other Metal)
Temperature levels T
3. Press the START/STOP button.
4. The unit performs a measurement cycle and directly displays the
compensated resistance value and, depending on set-up, displays one
of the following:
Programmed ambient temperature level
Temperature level measured by the temperature sensor
“- - - -” if the temperature sensor is activated but is incorrectly
connected or not connected at all
Measured temperature is out of range (14 to 131°F [-10° to 55°C])
If the temperature is out of range or if the sensor leads are disconnected, the
Model 6255 displays “Err 10”.
Temperature compensation can be toggled ON or OFF after the meas urem ent is
completed, in resistive and inductive modes or at any time in AUTO mode.
followed by T
ref
amb
4.7. Activating Alarms
The alarm programming menu offers the option of choosing one or two alarm
thresholds. An alarm comprises a value, an activation direction (above ▲ or
below ▼ the set point) and a sound level setting for the buzzer, should the alarm
become active.
Alarms are activated by successively pressing the 2nd button
followed by the ALARM button.
The display will indicate one of the following after each set of button presses:
Alarm 1 and the activation direction, ▲ or ▼
Alarm 2 and the activation direction, ▲ or ▼
Alarm 1 and Alarm 2 and activation directions, ▲ or ▼ for each
These values and direction parameters are programmable. See Setting an Alarm
Set Point, Direction and Buzzer Levels (§4.2.12). The buzzer will sound when
Alarm 1 and/or Alarm 2 threshold values are reached.
36 Micro-Ohmmeter Model 6255
5. MEMORY/PRINTING
5.1. Managing and Printing the Data in Memory
The memory is organized into locations called Objects and Tests.
There are 99 objects, each containing a maximum of 99 tests (measurements).
The maximum number of measurements that can be stored is approximately
1500.
After taking a measurement, it may be stored in memory by pressing the MEM
button. The MEM icon blinks and the first available Object and Test location for
storing this measurement is displayed with the last digit of the test number
blinking.
Example: Object 1 and Test 4 are displayed and the 4 will be blinking.
01:04.
OBJ : TEST
The object and test location can be changed using the arrow buttons.
FREE is displayed when the location is empty
OCC is displayed when the location has data stored in it
After choosing the measurement’s memory location, pressing the MEM button a
second time validates memory storage in a FREE location.
If an occupied location is selected, the OCC message blinks to warn that this
memory location is already taken. Storage action in this location requires
pressing the MEM button again. The previous measure men t in this loc atio n w ill
be replaced by the new measurement.
Micro-Ohmmeter Model 6255 37
5.2. Displaying and Printing Stored Measurements
To display or print a measurement result stored in memory, press
the yellow 2nd button followed by the MR button.
The measurement value for the last object and test saved is displayed.
Example: Object 1 and Test 3 are displayed.
01:03.
OBJ : TEST
The test unit number will be blinking. In this example the 3 will be blinking.
Change the object and test numbers using the arrow buttons. As you change
memory locations, the stored measurement value will be displayed. The following
measurement components are also accessible if stored.
The selected memory location will display:
Number of the object and test that correspond to the memory location
Active range and current level during the measurement
Measurement value with any compensation used
Alarm icon for any active alarms that occurred during the measurement
The parameters set for the alarm threshold, r efer enc e te mpe rature, amb ien t
temperature and metal correction coefficient are not directly accessible. They are
accessible by pressing the following:
Press the R ( ) button to display ambient temperature at the time of the
stored measurement.
Press the R ( ) button a second time to display the reference
temperature that the measurement was compensated to.
Press the button to display the type of metal and alpha value
used for compensation at the time of the measurement.
Press the PRINT button to print the measurement results stored at the
current memory location. An optional serial printer is required for this
feature.
Only memory locations with stored measurements are accessible.
38 Micro-Ohmmeter Model 6255
Measurement data stored in memory can be accessed directly from any
switch position except OFF and SET-UP for printing.
Press the yellow 2nd button followed by the PRINT MEM button to
access measurement results stored in memory for printing. An optional
serial printer is required for this feature. Use the arrow buttons to select
the object and test to be printed.
A typical printed report using an optional printer is show n below.
Figure 5-1
Blank report forms can be downloaded from the AEMC web site. Visit
www.aemc.com/techinfo/index.asp and open the Micro-Ohmmeters link.
Micro-Ohmmeter Model 6255 39
5.3. Cables and Printers Used with the Interface Port
The DB9 interface port can be used to trigger remote measurements
(“TRIG”). Wiring for remote triggering of a test is illustrated in Figure 5-2. The
“READY” LED indicates that a measurement can be made.
Figure 5-2
The DB9 interface port can be used for RS-232 communication with a PC,
terminal or a printer. The main connection pins used are shown in Figures 5-3
and 5-4 respectively.
Connection to a PC or Terminal:
Male Connector Female Connector
Printer end Printer end
Pin 6255 end
RX 2 3 TX
TX 3 2 RX
Gnd 5 5 Gnd
Figure 5-3
40 Micro-Ohmmeter Model 6255
Direct Printer Connection:
Male Connector Female Connector
Printer end Printer end
Pin Pin
RX 2 3 TX
TX 3 2 RX
Gnd 5 5 Gnd
CTS 8 8 CTS
Figure 5-4
Micro-Ohmmeter Model 6255 41
6. DATAVIEW
DataView software with the Micro-Ohmmeter Control Panel (provided free with
the product in North America, South America, and Australia) allows you to:
Connect the instrument to a computer
Configure and schedule a recording session on the instrument
Download recorded data from the instrument to the computer
Generate reports from downloaded data
To install DataView on a computer:
For more information, consult t he DataView Micro-Ohmmeter Control Panel Help.
View instrument measurements in real time on the computer
Do not connect the instrument to the computer before installing the
software and drivers.
1. Insert the USB drive that comes with the instrument into a USB port on
your computer.
2. If Autorun is enabled, an AutoPlay window appears on your screen.
Click “Open folder to view files” to display the DataView folder. If
Autorun is not enabled or allowed, use Windows Explorer to locate and
open the USB drive labeled “DataView.”
3. When the DataView folder is open, find the file Setup.exe and doubleclick it.
4. The Setup screen appears. This enables you to select the la nguage
version of DataView to install. You can also select additional install
options (each option is explained in the Description field). Make your
selections and cli c k Install.
5. The InstallShield Wizard screen appears. This program leads you
through the DataView install process. As you complete these screens,
be sure to check Micro-Ohmmeters when prompted to select features to
install.
6. When the InstallShield Wizard finishes installing DataView, the Setup
screen appears. Click Exit to close. The DataView folder appears on
your computer desktop.
7. Open the DataView folder on your desktop. This displays a list of icons
for the Control Panel(s) installed with DataView.
8. Open the DataView Micro-Ohmmeter Control Panel by clicking the
icon.
42 Micro-Ohmmeter Model 6255
7. TROUBLESHOOTING
The Model 6255 incorporates internal diagnostics and will inform the operator of
any condition needing attention through the use of error messages. The available
messages are described here.
7.1. Fault Indicators
Err 1 Low battery level
Err 2 Internal problem
Err 3 Unable to measure battery
Err 4 Unable to measure temperature
Err 5 Internal temperature too high - let the instrument cool down
Err 6 Unable to establish current measurement
Err 7 Measurement out of range
Err 8 Internal problem
Err 9 Measurement cycle stopped
Err 10 Temperature sensor incorrectly connected or missing
Err 11 Current leads incorrectly connected
Err 12 Voltage leads incorrectly connected or measured resistance too
high
Err 13 Residual voltage too high
Err 21 Adjustment out of range
Err 22 Measured value out of range
Err 23 Entry out of range
Err 24 Unable to write to memory
Err 25 Unable to read memory
Err 26 Memory full
Err 27 Memory empty; no data available
Err 28 Memory check problem
Err 29 Object or test number incorrect
WARNING: If error message 2, 3, 4, or 8 appears, the instrument
must be sent to a qualified organization for repair. See the Repair
and Calibration section of this manual for return instructions.
Micro-Ohmmeter Model 6255 43
8. APPLICATION EXAMPLES
WARNINGS:
The proper procedures for using the Model 6255 in some specific applications
are described in this section.
8.1. Measuring Winding Resistance of Motors and Transformers
Prior to and after testing a transformer winding, the energy stored in
the magnetic field must be dissipated by shorting the tran sformer
terminals. For additional safety, the transformer terminals should be
jumpered together before the instrument is disconnected.
One terminal of the test specimen should be grounded for
safety!
Make connections to the transformer as shown in Figure 8-1. On larger
transformers, the measurement stabi lizat io n time will incr ease.
Figure 8-1
44 Micro-Ohmmeter Model 6255
8.2. Measuring Resistance on Electric Motors
For this test, Kelvin probes should be used (Figure 8-2). Make contact with each
segment on the motor commutator. Allow approximately two seconds for the
display to stabilize.
Figure 8-2
8.3. Battery Strap Measurements
Proper battery strap resistance measurements will help ensure proper voltage
output. The resistance on battery strap connections should be measured using
the Kelvin probes (see Figure 8-3). Measurements must be made with the
system power turned off.
The average resistance of all the intercell connections should be determined by
totaling the individual resistances and dividing by the number of connectors.
Each individual cell resistance should not exceed the average by more than 10%.
See the manufacturer’s specifications for typical resistance values.
Figure 8-3
Micro-Ohmmeter Model 6255 45
9. MAINTENANCE
Use only factory specified replacement parts. AEMC
for any accident, incident, or malfunction following a repair done other than by its
service center or by an approved repair center.
9.1. Warning
To avoid electrical shock, do not attempt to perform any servicing
unless you are qualified to do so.
Do not perform any service while the micro-ohmmeter is on any circuit.
To avoid electrical shock and/or damage to the instrument, do not allow
water or other foreign agents into the electronic module.
Make sure the internal battery is fully charged prior to testing. If the
instrument has been left unused for several months, recharge the
battery.
We recommend recharging the micro-ohmmeter every month to ensure
a full battery charge when used.
When replacing fuses, install only fuses which are direct replacements.
9.2. Cleaning
WARNING: Disconnect the instrument from any source of
electricity.
If the case needs cleaning, do not use any alcohol or oil based cleaners.
Preferably use soapy water with a damp cloth or sponge.
Dry immediately after cleaning. Avoid water penetration into the
electronic module.
Make sure the micro-ohmmeter and all leads are dry before further use.
9.3. Charging/Recharging the Battery
AC POWER SELECTION
The Model 6255 may be recharged from 90 to 264VAC (45 to 420Hz). The
instrument includes a 110V line cord, which provides the charging voltage for the
rechargeable battery.
CHARGING THE BATTERY
The Model 6255 should be fully charged before using it for the first time. This
may take up to 6 hours for a completely discharged battery.
If the battery symbol is flashing, the battery needs to be recharged. The
battery will charge in both the ON and OFF mode.
ON mode, the charging indicators will show on the display.
OFF mode, no display will show during charging.
®
will not be held responsible
46 Micro-Ohmmeter Model 6255
Connect the Model 6255 to 12 0VAC using the power cord provided (charging
starts automatically).
Testing cannot be conducted while charging the batteries. Button
presses are ignored when charging is in process.
CHARGING INDICATORS
bAt on the small display and CHrg on the main display, signifies fast
charging in progress.
bAt on the small display and CHrg flashing on the main dis play ,
signifies slow charging (starts off with fast charge, temperature
conditions permitting).
bAt on the small display and FULL on the main display, signifies that
charging is complete.
If the instrument is turned ON and the battery voltage is >5V, normal use of the
device is permitted.
9.4. Battery and Fuse Replacement
Ensure no terminals are connected and that the switch is in the OFF
position before opening the front panel.
BATTERY
Replacing the battery causes data to be lost from the memory.
The battery should only be replaced by a qualified technician or sent
back to the factory for replacement and standard calibration. See the
Repair and Calibration section for return instructions.
FUSES
Before replacing the internal batteries or fuses, the front panel must first
be removed. Use a Phillips head screwdriver to remove the four screws
from the feet on the bottom of the case.
Pull out the chassis from the top.
The two fuses are located on the left side of the chassis.
F1 is located near the C1 and P1 terminals.
F2 is located directly below on the bottom power supply board
assembly.
Fuse F1, is 0.25 x 1.26” (6.3 x 32mm) fa st acti ng, 16A /2 50V , low
internal resistance, protecting the current source from outside voltages
on energized specimens.
Fuse F2, is 0.2 x 0.79” (5.0 x 20mm) fast acting, 2A/250V, protecting the
battery charger power supply board.
Micro-Ohmmeter Model 6255 47
REPAIR AND CALIBRATION
To ensure that your instrument meets factory specifications, we recommend that
it be scheduled to be sent back to our factory Service Center at one-year
intervals for recalibration, or as required by other standards or internal
procedures.
For instrument repair and calibration:
You must contact our Service Center for a Customer Service Authorization
Number (CSA#). This will ensure that when your instrument arrives, it w ill be
tracked and processed promptly. Please write the CSA# on the outside of the
shipping container. If the instrument is returned for calibration, we need to know if
you want a standard calibration or a calibration traceable to N.I.S.T. (includes
calibration certificate plus reco r ded calibr at ion data).
For North / Central / South America, Australia and New Zealand
Ship To: Chauvin Arnoux
15 Faraday Drive • Dover, NH 03820 USA
Phone: (800) 945-2362 (Ext. 360)
Fax: (603) 742-2346 • (603) 749-6309
E-mail: repair@aemc.com
(Or contact your authorized distrib utor.)
Costs for repair, standard calibration, and calibration traceable to N.I.S.T. are
available.
NOTE: You must obtain a CSA# before returning any instrument.
®
, Inc. d.b.a. AEMC® Instruments
(603) 749-6434 (Ext. 360)
TECHNICAL AND SALES ASSISTANCE
If you are experiencing any technical problems, or require any assistance with
the proper operation or application of your instrument, please call, fax, or e-mail
our tech nical support team:
®
Contact: Chauvin Arnoux
Phone: (800) 343-1391 • (508) 698-2115
Fax: (508) 698-2118
E-mail: techsupport@aemc.com
, Inc. d.b.a. AEMC® Instruments
48 Micro-Ohmmeter Model 6255
LIMITED WARRANTY
Your device is warranted to the owner for a period of two years from the date of
original purchase against defects in manufacture. This limited warranty is given
by AEMC
warranty is void if the unit has been tampered with, abused, or if the defect is
related to service not performed by AEMC
Full warranty coverage and product registration is available on our website at:
www.aemc.com/warranty.html.
Please print the online Warranty Coverage Information for your records.
Warranty Repairs
What AEMC® Instruments will do:
If a malfunction occurs within the warranty period, you may return the instrument
to us for repair, provided we have your warranty registration information on file or
a proof of purchase. AEMC
faulty material.
What you must do to return an Instrument for Warranty Repair:
First, request a Customer Service Authorization Number (CSA#) by phone or by
fax from our Service Department (see address below), then return the instrument
along with the signed CSA Form. Please write the CSA# on the outside of the
shipping container. Return the instrument, postage or shipment pre-paid to:
Ship To: Chauvin Arnoux
®
Instruments, not by the distributor from whom it was purchased. This
®
Instruments.
®
Instruments will, at its option, repair or replace the
®
, Inc. d.b.a. AEMC® Instruments
15 Faraday Drive • Dover, NH 03820 USA
Phone: (800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax: (603) 742-2346 • (603) 749-6309
E-mail: repair@aemc.com
Caution: To protect yourself against in-transit loss, we recommend you insure
your returned material.
NOTE: You must obtain a CSA# before returning any instrument.
Micro-Ohmmeter Model 6255 49
NOTES
50 Micro-Ohmmeter Model 6255
NOTES
Micro-Ohmmeter Model 6255 51
01/18
99-MAN 100458 v1
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
15 Faraday Drive • Dover, NH 03820 USA
Phone: (603) 749-6434 • Fax: (603) 742-2346
www.aemc.com
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