Avtron T477W User manual

Note: Revisions on August 28, 2018, February 21, 2018,
August 4, 2014, April 18, 2014, January 5, 2012, and
November 23, 2009 affected formatting and company
name changes. Last change affecting technical
information was dated June 15, 2004.
Avtron Aerospace, Inc.
...........................................................................................................................
Avtron Model T477W
Bonding Meter
with B14703 Battery Pack
Replacement Instructions
Part Number T477WC15292
...........................................................................................................................
December 11, 1981
Revised August 28, 2018
Copyright © 2012 Avtron Aerospace, Inc.
T.O. 33DA39-71-1
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the
Export Administration Regulations (EAR), 15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-
U.S. person (individual or company), whether in the United States or abroad, without any required export license or other approval from the
U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
To buy, sell, rent or trade-in this product please click on the link below:
https://www.avionteq.com/Avtron-T477W-Bonding-Meter
www.avionteq.com

Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.

Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
PROPRIETARY NOTE
This document contains information PROPRIETARY to Avtron Aerospace, Inc. It is furnished solely to provide
information sufficient for instruction, operation, maintenance, evaluation, and testing of the equipment herein
disclosed; is not to be used for manufacturing or procurement; and is not to be disclosed to anyone other than
persons in the Division, or the Company, or the Government, as the case may be, responsible for action relating
to this document without the express written permission of Avtron Aerospace, Inc.
WARRANTY
The last page of this document contains an express limited warranty. The provisions of this warranty cover any and
all rights extended to holders of Avtron equipment.
Rev. November 1, 2011

Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Table of Contents
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
i
Table of Contents
1 DESCRIPTION.......................................................................................................................................................................1-1
2 OPERATING INSTRUCTIONS.............................................................................................................................................2-1
2.1 Initial Operation .........................................................................................................................................................2-1
2.2 Battery Charging ........................................................................................................................................................2-1
2.3 Probes .........................................................................................................................................................................2-1
2.4 Minimizing Error Contributed by Probes...................................................................................................................2-2
2.5 C22161 Probe Set .......................................................................................................................................................2-2
2.6 C15479 Probe Set (Optional) .....................................................................................................................................2-3
2.7 C15478 and C15480 Probe Sets (Optional)................................................................................................................2-4
2.8 C16695 Probe Set (Optional) .....................................................................................................................................2-4
2.9 Custom Probe Sets......................................................................................................................................................2-4
2.10 Meter Operation .........................................................................................................................................................2-5
2.11 Leading “1” Display...................................................................................................................................................2-5
2.12 Erratic Digits ..............................................................................................................................................................2-5
2.13 Flashing Decimal Points.............................................................................................................................................2-5
2.14 Battery Endurance ......................................................................................................................................................2-6
3 CIRCUIT DESCRIPTION ......................................................................................................................................................3-1
4 CALIBRATION AND MAINTENANCE PROCEDURES ...................................................................................................4-1
4.1 Calibration ..................................................................................................................................................................4-1
4.2 Field Calibration Procedure........................................................................................................................................4-1
4.3 Calibration Period or Frequency.................................................................................................................................4-3
4.4 Maintenance ...............................................................................................................................................................4-3
4.5 Preventive Maintenance .............................................................................................................................................4-3
4.6 Battery Testing ...........................................................................................................................................................4-4
4.7 Meter Shutdown .........................................................................................................................................................4-4
5 TROUBLESHOOTING ..........................................................................................................................................................5-1
5.1 Battery Problems ........................................................................................................................................................5-1
6 BATTERY CHARGING ........................................................................................................................................................6-1
7 APPENDIX - BATTERY TESTING......................................................................................................................................7-1
7.1 BATTERY TESTING................................................................................................................................................7-1
8 B14703 BATTERY PACK REPLACEMENT INSTRUCTIONS..........................................................................................8-1
8.1 Battery Replacement Instructions...............................................................................................................................8-1

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Table of Contents
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
ii
9 ESD PRECAUTIONARY GUIDELINES ..............................................................................................................................9-1
10 REPLACEMENT PARTS LIST ...........................................................................................................................................10-1
10.1 Introduction ..............................................................................................................................................................10-1
10.2 Reference Designators..............................................................................................................................................10-1
Table of Figures
Figure 2-1. Two Pistol Grip Probes with a Pair of Probe Tips..................................................................................................... 2-2
Figure 2-2. Optional Probe Sets ................................................................................................................................................... 2-3
Figure 2-3. Flashing Decimal Points............................................................................................................................................ 2-5
Figure 7-1. Battery Test Schematic.............................................................................................................................................. 7-1
Figure 8-1. Battery Pack Location ............................................................................................................................................... 8-2
Drawing(s)
SB1242 Outline Drawing

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Description
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
1-1
1DESCRIPTION
The Model T477W Bonding Meter is a precision instrument using digital techniques to identify the integrity of electrical connections
by measuring and displaying small values of resistance (less than 2 ohms). The range of measurement is 0.2 to 2000 milliohms.
Resistance measurements smaller than 0.2 milliohms are possible with reduced accuracy.
The T477W Bonding Meter is supplied with a set of probes having four wire (Kelvin) connections. In addition, a separate power
supply is provided for charging the T477W batteries.
The T477W Bonding Meter is certified by Underwriter Laboratories per UL 913 as an intrinsically safe device for use in hazardous locations,
Class I--Group A, B, C, or D. These locations are identified by the National Electrical Code, National Fire Protection Association (NFPA)
document number 70, and are typified by the presence of flammable vapors such as hydrogen, propane, methane, and gasoline.
SPECIFICATIONS
RANGES AND
ACCURACY
NOTE:
Accuracy expressed as: +/- (% of
reading + x digits). Please refer to
probe descriptions for additional
accuracy considerations.
2 milliohms (C15479 and C16695 probes only)
2 milliohms (C22161 probe only)
20 milliohms
200 milliohms
2000 milliohms
+/- (1% + 5 )
+ (1% + 30) and – (1% + 10)
+/- (1% + 5 )*
+/- (1% + 5 )*
+/- (1% + 5 )*
* Applies to T477W used with
C15479, C16695, and C22161
probes only
OUTPUT:
Maximum Current Output
Maximum Voltage Output
200 mA rms
200 mV rms, 500 mV(p-p)
WEIGHT:
T477W
T477W, Probe Set, Charger and Case
3.22 lbs. / 1.46 kg
8.26 lbs. / 3.75 kg
C A U T I O N
**ESD** The Model T477W Bonding Meter contains Class I parts and
assemblies susceptible to damage by electrostatic discharge (ESD). Refer to
MIL-STD-1686A for ESD protective procedures.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Description
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
1-2

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Operating Instructions
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
2-1
2OPERATING INSTRUCTIONS
2.1 Initial Operation
The T477W Bonding Meter is shipped with charged batteries. If the meter is not used for a period of 30 days following
shipment, the batteries should be charged before use.
2.2 Battery Charging
Batteries are recharged by disconnecting the probe from the input connector J1 and connecting the battery charger B15693 to
connector J1. Batteries should nominally be charged for 14-16 hours. Continuous charging for prolonged periods (weeks or
months) is not recommended. Refer to Section VI for further details on battery charging and power sources other than 120
VAC, 60 Hz.
W A R N I N G
Do not attempt to charge batteries in hazardous locations. Battery charging should
be done only in a location known to be free from flammable gases or vapors.
2.3 Probes
One set of probes, Part Number C22161, is supplied with the T477W Bonding Meter. There are four optional probe sets
available that may be purchased separately. All of the probe sets are useful for particular applications; however, care must be
exercised in the use and selection of probes. The use of a particular probe set depends on the size and shape of the two bonded
materials in the vicinity of the bond. Below is a brief description of each:
Part Number Description
C22161 Two Pistol Grip probes with a pair of probe tips on each
C15479 Two single point (current) clamps and two pencil style voltage probes
C15478 Compass style probe and dual point clamp
C15480 Dual compass style probes
C16695 Four pencil style probes
Reference the optional probe set sketches in Figure 2-2.
When making a measurement, always place the voltage leads closest to the bond being measured for better accuracy.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Operating Instructions
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
2-2
C A U T I O N
Probes are equipped with sharp points. Exercise caution when handling probes to
prevent puncture wounds or scratches.
2.4 Minimizing Error Contributed by Probes
The above probe sets consist of two current leads which connect the Bonding Meter regulated current output to the unknown
resistance and two voltage sensing leads to measure the voltage developed across the unknown. The voltage sensed is small and
the current is alternating; therefore, a small transformer effect (coupling) exists between the current sourcing and voltage sensing
leads. This effect is best minimized when the voltage sensing leads are separate from the current leads and bound together for the
majority of the length of the cable as in the C15479 and C16695 probe sets. The distance that the voltage sense leads are spread
from each other is to be considered the cable loop diameter. The amount of meter reading error caused by the coupling effect on
metal surfaces is directly proportional to the cable loop diameter. Minimizing the cable loop diameter with any of the five probe
sets is advised to achieve the most accurate reading possible. See Figure 2-1.
2.5 C22161 Probe Set
This probe set utilizes two pistol grip style probes that facilitate obtaining a quick and easy reading. The best-rated meter
accuracy is obtained with the C22161 probe set, except in the 2 milliohm range. The accuracy in the 2 milliohm range is +
(1% of reading + 30 digits) and – (1% of reading + 10 digits).
NOTE
Each pistol grip probe is labeled “P” and “C” indicating which pin is for potential (voltage) and
current.
In the 2 milliohm range, reduce the cable loop diameter (see Figure 2-1) as much as possible to
minimize reading errors.
Figure 2-1. Two Pistol Grip Probes with a Pair of Probe Tips

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Operating Instructions
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
2-3
2.6 C15479 Probe Set (Optional)
These probes (Figure 2-2) have separate current and voltage leads, and the voltage sensing leads are bound together for nearly
the full length of the cable, which best minimizes the coupling effect described above. The best-rated meter accuracy is
obtained with this probe set when connected such that the meter reading is positive only. This probe set may be used for
calibrating the T477W Bonding Meter and whenever measurement accuracy is crucial.
NOTE
The red clamp and pencil style probe are positive current and voltage respectively while the black
clamp and pencil style probe are negative current and voltage respectively. The polarity signs on
the clamps have no meaning. Older probe sets current clamps and voltage pencil probes polarities
are determined solely by the lead color wired to them.
Figure 2-2. Optional Probe Sets
C15292B1SCAN

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Operating Instructions
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
2-4
2.7 C15478 and C15480 Probe Sets (Optional)
These probe sets (Figure 2-2) do not have separate current and voltage leads. Their use may cause meter reading error
exceeding the allowed tolerance due to the coupling effect. They should only be used for survey work to establish an
approximate resistance.
Meter reading error caused by the use of probe sets C15478 and C15480 depends on the probe lead configuration. In order to
identify the magnitude of error, tests have been conducted using a wooden surface to simulate air and an aluminum sheet to
simulate an aircraft structure. Meter error on wooden surfaces was on the order of 20 digits. Error measured on the aluminum
surface ranged from 20 to 240 digits, depending on the size of the cable loop formed. When using the C15478 and C15480,
form the smallest possible cable loop diameter (see Figure 2-1).
NOTE
The current and voltage leads are identified by the following GRIP COLOR CODE:
Black is for positive and negative current.
Red is for positive and negative voltage.
(Additionally, on the compass style probes, the blunt spring-loaded tip is voltage, while the pins
are current.)
On the C15478 and C15480 probe sets sold after November 1989, Avtron Aerospace, Inc. has
enhanced their design by adding sleeving to the first 40 inches of the cables. This helps to
minimize the meter reading error induced by the coupling effect.
The polarity signs imprinted on the clamps of these probes have no meaning.
2.8 C16695 Probe Set (Optional)
These probes (Figure 2-2) have separate current and voltage leads, and the voltage sensing leads are bound together for nearly
the full length of the cable, which best minimizes the coupling effect. The best-rated meter accuracy is obtained with this
probe set when connected such that the meter reading is positive only. This probe set may be used for calibrating the T477W
Bonding Meter and whenever measurement accuracy is crucial. Since all the probes are of the pencil type, they are well suited
for taking accurate measurements on small parts or in cramped space locations.
NOTE
The black pencil style probes are positive and negative current while the red pencil style probes
are positive and negative voltage. Make sure to observe polarity while making a measurement
such that the voltage and current probes on each side of the bond are of the same lead color.
2.9 Custom Probe Sets
T477W probe sets are constructed with extensive use of non-sparking materials such as aluminum, brass, and copper. This
design minimizes the possibility of spark ignition if the probes are dropped and happen to strike a surface. The fabrication of
custom-made probes is not recommended.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Operating Instructions
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
2-5
2.10 Meter Operation
Select one of the five probes and connect it to the front panel J1. In making a measurement, make sure that the probe tips
penetrate any non-conductive film that may be present (and there are no flashing decimal points or erratic digits flickering in the
display). The accuracy is known only when the meter reading is positive. Momentarily press the TEST button located on the
front panel. The TEST button not only turns on the display but also changes the meter range. The first TEST button activation
causes the meter to operate at the 2 milliohm range. Subsequent activations of the TEST button will change the range from 2 to
20 to 200 to 2000 and back to 2 milliohms. The decimal point is automatically positioned for each range.
In order to conserve battery power, a built-in timer automatically shuts off the display after 52 seconds of operation. The
display may be illuminated by pressing the LAMP button located on the front panel. Meter range is not affected by the lamp
button; however, meter shutdown timing is delayed while the lamp button is activated.
2.11 Leading “1” Display
A leading “1” display indicates an over-range condition. If the display indicates a leading 1 (as in Figure 3), press the test
button once to advance to the next highest range. If the meter is over-ranging in the 2000 milliohm range, then the unknown
resistance is greater than 1999 milliohms and is out of the range of the Bonding Meter.
2.12 Erratic Digits
Erratic digits (erratic numbers flickering in the display) are an indication that the voltage sense connections are open or a large
over-range condition exists. Ensure that the voltage sense probes are making a good, low resistance connection. Advance the
range using the test button if necessary.
2.13 Flashing Decimal Points
Flashing decimal points are an indication that the resistance of the path formed by the current probes is excessive. This is
most common in the 2 milliohm range. The 2 milliohm range requires a current probe path of less than 200 milliohms.
Ensure that the current probes are making a good, low resistance connection.
1.___ Overrange on the 2 milliohm range
1_.__ Overrange on the 20 milliohm range
1__._ Overrange on the 200 milliohm range
1____ Overrange on the 2000 milliohm range
Figure 2-3. Flashing Decimal Points

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Operating Instructions
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
2-6
C A U T I O N
The T477W Bonding Meter accuracy is significantly affected by the presence of
direct current (DC) potentials on the unknown resistance. The presence of DC
potentials at or on the unknown resistance causes saturation of the output and
input transformers. Some small DC potential is tolerated; however, that potential
varies with the magnitude of the unknown resistance. DC potentials on the order
of 10 millivolts per milliohm cause no problem. When in doubt about the
presence of DC potentials, do not use the T477W Bonding Meter. Significant
meter damage may result.
2.14 Battery Endurance
The T477W is powered from internal rechargeable batteries. Battery endurance depends on capacity (amp/hours) which is
affected by the following factors:
Temperature - Capacity is rated for room temperature operation (25oC) and is tested for operation at –15 and
60oC. Operation above room temperature causes significant reduction in capacity.
Charge History - Capacity is based on a full charge within 10 days. To minimize charge loss (as much as 25% in
one month), batteries must be charged frequently. However, charging a battery repeatedly prior to
the “LO BAT” being illuminated in the display will cause a loss of endurance as the battery
develops a memory, which is characteristic of nickel cadmium cells. (Memory can sometimes be
erased; see Section 7.)
Age - The battery ages after many charge/discharge cycles. Its ability (capacity) to sustain a load after a
full charge is diminished. Thus the meter has a shortened operating time before a recharge is
necessary.
Battery endurance is rated under the worst conditions (50% capacity) to provide eight (8) hours of continuous operation
providing the battery has been charged not more than 10 days prior to the time of operation. New batteries (100% capacity)
are anticipated to have sufficient energy to make twice the rated measurements. Because the T477W has a built-in timer for
automatic shutdown after 52 seconds, "Continuous Operation" is defined in terms of the following 3-minute measurement
cycle:
26 seconds current probes connected to load
26 seconds current probes not connected to load
(including 2 seconds lamp operation)
128 seconds shutdown
Total: 180
When the battery is nearing discharge, a "LO BAT" indication is displayed on the left side of the meter display. Meter
readings remain accurate, but the batteries should be recharged.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Circuit Description
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
3-1
3CIRCUIT DESCRIPTION
The T477W is designed to measure values of resistance from 2000 milliohms to less than 0.2 milliohms. Connections to the unknown
resistance are made by four wire (Kelvin) connections that consist of two current and two voltage sensing leads. The meter circuit
provides a regulated alternating current @ 78 Hz that is fed through the unknown resistance while the voltage generated across that
unknown resistance is sensed. Since the sensed voltage is caused by a constant current, and voltage is proportional to resistance, the
meter interprets voltages in terms of resistance.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Circuit Description
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
3-2

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Calibration
and Maintenance Procedures
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
4-1
4CALIBRATION AND MAINTENANCE
PROCEDURES
4.1 Calibration
The circuit is composed of solid state devices which have been subjected to extensive testing and therefore few failures are
anticipated. However, periodic testing against a known resistance standard is recommended. Testing may be easily performed
using the K777 Verification Fixture. The meter may also be returned to Avtron Aerospace, Inc., for a complete calibration for
a reasonable fee as described below.
4.2 Field Calibration Procedure
Equipment required:
Avtron T477W, Part Number C15292 Bonding Meter (Unit Under Test)
Avtron K777, Part Number C15293 Calibration Test Fixture
Procedure:
1. Connect P1 of the K777 Calibration Test Fixture to J1 of the T477W Bonding Meter (Unit Under test).
2. Follow the table below to verify the accuracy of the Bonding Meter. For each K777 switch position in column one, set
the T477W to the range in column two by pressing the test button. Read the T477W display and compare to desired
value.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Calibration
and Maintenance Procedures
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
4-2
K777 T477W Tolerance T477W
Switch Milliohm (in milliohms) Display
Position Range Reading
Zero 2.000 +/-0.002* _______
0.10 2.000 +/-0.006 _______
1.00 2.000 +/-0.015 _______
1.00 20.00 +/-0.06 _______
10.0 20.00 +/- 0.15 _______
10.0 200.0 +/-0.6 _______
100 200.0 +/-1.5 _______
100 2000 +/-6 _______
1000 2000 +/-15 _______
* The 0.002 milliohm tolerance is an internal unpublished specification. The official published
specification is 0.005 milliohms for the 2 milliohm range. All other ranges are as published +/-
5 least significant digits for the allowable zero error.
3. This completes the field verification procedure. There are no user adjustable components. If an alignment failure is
found during the verification, contact Avtron Aerospace, Inc., to return the unit for repair.
NOTE
Perform the above field calibration procedure after a full charge while on a non-metallic work
surface without any other T477W Bonding Meters in the near vicinity.
The K777 unit provides a good field verification of the T477W Bonding Meter’s performance excluding the probes. The
probe sets should also be tested to verify that they provide proper readings with the Bonding Meter. Avtron provides
calibration service on both the T477W and the K777 products.
Our calibration service provides, in addition to the K777 test values, the following: environmental tests from 5 degrees to 140
degrees Fahrenheit; battery response/endurance at the preceding extremes, accuracy of the unit at the preceding extremes,
uncertainties induced from the different styles of probes, auto-shutoff time verification, charging waveform check, the unit’s
burden/threshold levels and additional measurement test points not available on the K777. The calibration includes a detailed
certificate and data if requested. Factory repair is available at additional cost if required.
Prior to sending equipment to Avtron Aerospace, Inc., for calibration or service, please contact us to receive an RMA number
and instructions on where to send the items. Please visit our website for contact and product information at
http://www.avtronaero.com/rma.htm.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Calibration
and Maintenance Procedures
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
4-3
4.3 Calibration Period or Frequency
As the manufacturer, Avtron suggests a calibration interval of one year. However, it is the sole responsibility of the end user
to determine an interval that satisfies their quality system requirements.
4.4 Maintenance
The T477W is composed of solid state components and requires minimal maintenance. Field repairs are not recommended.
Component substitution with other than approved Avtron parts may impair intrinsic safety, thus voiding the UL approval and
putting property and people at risk. It is recommended that a malfunctioning meter be returned to Avtron for repair.
W A R N I N G
Please note that breaking the tamper seal on the T477W Bonding Meter for any
reason whatsoever shall relieve Avtron Aerospace, Inc., of any and all liability
with regard to personal injury or property damage, whether directly or indirectly
resulting from the use of the meter. Warranty claims on meters with a broken
tamper seal may be honored only after an evaluation of the meter is performed by
Avtron.
4.5 Preventive Maintenance
The T477W is powered by rechargeable nickel cadmium batteries.
The battery pack is the most likely component in the T477W to require maintenance. The pack is potted to ensure proper
operation of current limiting resistors which were required for safety certification by Underwriter Laboratories. The potting
makes battery replacement awkward and expensive, but it is necessary for safety. Battery preventive maintenance procedures
have been developed to identify battery problems before they become serious.
Nickel cadmium batteries are reliable and will provide hundreds of charge/discharge cycles. Relatively frequent use is
recommended and batteries should be discharged to the point the “LO BAT” indicator is displayed before recharging. The
most common battery problems anticipated are over-discharged, overcharged, and short cycled batteries.
Over-discharge occurs when the T477W is used following the "LO BAT" display. Over-discharging may cause batteries to
become depleted to the point where one or more battery cells have reversed current flow. Furthermore, extremely deep
discharge may obstruct automatic shutdown of the meter display.
Overcharging occurs when the T477W is placed on charge continuously for weeks or months. This will cause some drying of
the battery and the possibility of reduced capacity.
Short cycled usage is encountered when fully charged batteries are partially discharged and then fully recharged. Short
cycling causes battery capacity to be progressively reduced and has been referred to as memory conditioning. Generally, but
not always, a reconditioning process in which the battery is given several deep discharge/charge cycles corrects a short cycled
memory.

Avtron Model T477W Bonding Meter
with B14703 Battery Pack Replacement Instructions
Part Number T477WC15292
Calibration
and Maintenance Procedures
Subject to the EAR, ECCN [9E610.a]. This information is subject to the export control laws of the United States, specifically including the Export Administration Regulations (EAR),
15 C.F.R. Part 730 et. seq. Transfer, retransfer, or disclosure of this data by any means to a non-U.S. person (individual or company), whether in the United States or abroad, without any
required export license or other approval from the U.S. Government is prohibited, including without limitation any diversion to a military end user or use in a military end use application.
4-4
4.6 Battery Testing
It is recommended that the T477W battery pack be periodically tested to identify problems before they become serious. One
method of testing the battery pack is to load it with 22 ohm, 2 watt resistor, and measure the terminal voltage. It should be 4
volts + or -0.2 volts for a fully charged battery. A better test to ensure battery capacity is to make a time-current test as
described in the Appendix, Section 7.
W A R N I N G
In order to retain Underwriter Laboratory certification and to permit safe use
in hazardous locations, replace defective batteries with Avtron part number
B14703 only.
Substitution of ordinary batteries for a defective battery pack may impair safe meter operation in a flammable environment.
The batteries and current limiting resistors contained in the Avtron battery pack are needed to ensure safety. The testing
procedures outlined in the appendix will be helpful in avoiding unnecessary replacement.
4.7 Meter Shutdown
The meter is supplied with a timer set to provide 52 seconds of operating time. This time may be lengthened or shortened by
Avtron Aerospace, Inc., during a calibration at no charge if requested.