Valhalla 4176 User manual

Operation Manual
Model 4176
Programmable Micro-Ohmmeter
VALHALLA
SCIENTIFIC
Need Help? Call 800-548-9806.
www.valhallascientific.com
©2015 Valhalla Scientific, Inc. All Rights Reserved.

VALHALLA SCIENTIFIC INC. CERTIFICATION
VALHALLA SCIENTIFIC INC. WARRANTY STATEMENT
Valhalla Scientific Inc. certifies that this instrument was thoroughly tested, inspected, and found to
meet published specifications when shipped from the factory. Valhalla Scientific, Inc. further certifies
that its calibration measurements are traceable to the National Institute of Standards and Technology to
extent allowed by N.I.S.T.’s calibration facility.
Due to continuing product refinement and due to possible parts manufacturer change, Valhalla
Scientific, Inc. reserves the rights to change any or all specifications without notice.
The warranty period for this instrument is stated on your invoice and packing list. Please refer to these
to determine appropriate warranty dates.
Valhalla Scientific, Inc. will repair the instrument during the warranty period provided it is return to
our repair and calibration facility freight prepaid. No other warranty is expressed or implied.
Valhalla Scientific, Inc. is not liable for consequential damages.
Permission and a Return Material Authorization number (RMA) must be obtained directly from the
factory for warranty repairs. No liability will be accepted if returned without such permission.
4176 Programmable µ-Ohmmeter User & Maintenance
Manual
Edition 1
Copyright © 2004-2005 Valhalla Scientific, Inc. All rights
reserved

Edition 1 …………………………………………………………………….….November, 2004
All Editions and Updates of this manual and their creation date are listed below. The first edition of
the manual is 1. The edition number increases by 1 whenever the manual is revised. Updates, which
are issued between editions, contain replacement pages to correct or add additional information to the
current Edition of the manual. Whenever a new Edition is created, it will contain all of the update
information for the previous Edition. Each new Edition or Update also includes a revised copy of this
documentation history page.
D OCUMENTATION HISTORY

WARNING, RISK OF
ELECTRICAL SHOCK.
Frame or chassis ground terminal
--- typically connects to the
equipment’s metal frame.
Indicates the field wiring terminal
that must be connected to ground
before operation the equipment ---
protects against electrical shock in
case of fault.………………………
Alternating current (AC)
Direct current (DC)
Calls attention to a procedure,
practice, or condition that could
possibly cause damage to
equipment or permanent loss of
data.……………………………….
WARNING
Calls attention to a procedure,
practice, or condition that could
cause bodily injury or death.
Instruction manual symbol affixed
to product. Indicates that the user
must refer to the user manual for
specific WARNING or CAUTION
information to avoid personal
injury or damage to the product.
SAFETY SYMBOLS
CAUTION

The following general safety precautions must be observed during all phases of operation, service, and
repair of this product. Failure to comply with these precautions or with specific warnings elsewhere in this
manual violates safety standards of design, manufacture, and intended use of the product. Valhalla
Scientific assumes no liability for the customer’s failure to comply with these requirements.
Ground the equipment: For Safety class 1 equipment (equipment having a protective earth terminal), an
interrupted safety earth ground must be provided from the main power source to the product input wiring
terminals or supplied power cable.
DO NOT operate the product in an explosive atmosphere or in presence of flammable gases or fumes.
For continued protection, replace the line fuse(s) only with fuse(s) of the same voltage and current rating
and type. DO NOT use repaired fuses or short-circuited fuse holders.
Keep away from live circuits: Operating personnel must not remove equipment covers or shields.
Procedures involving the removal of covers or shields are for the use of service-trained personnel only. Under
certain conditions, dangerous voltage may exist even with the equipment switched off. To avoid dangerous
electrical shock, DO NOT perform procedures involving cover or shield removal unless you are qualified
to do so.
DO NOT operate damaged equipment: Whenever it is possible that the safety protection features built
into this product have been impaired, either through physical damage, excessive moisture, or any other reason,
REMOVE POWER and do not use the product until safe operation can be verified by service-trained
personnel. If necessary, return the product to Valhalla Scientific for service and repair to ensure that safety
features are maintained.
DO NOT service or adjust alone: Do not attempt internal service or adjustment unless another person,
capable of rendering first aid and resuscitation, is present.
DO NOT substitute parts or modify equipment: Because of the danger of introducing additional
hazards, do not install substitute parts or perform any unauthorized modification to the product. Return the
product to Valhalla Scientific for service and repair to ensure that safety features are maintained.
Measuring high voltage is always hazardous: ALL multimeters input terminals (both front and rear)
must be considered hazardous whenever inputs greater than 42V (dc or peak) are connected to ANY input
terminal.
Permanent wiring of hazardous voltage or sources capable of delivering grater than 150VA should be
labeled, fused, or in some other way protected against accidental bridging or equipment failure.
DO NOT leave measurement terminals energized when not in use.
W ARNINGS

P REFACE
This manual contains installation, operating and programming, and configuration information for the
Valhalla Scientific, Inc. Model 4176 Programmable µ-Ohmmeter.
The manual consists of the following chapters:
C HAPTER 1 I NSPECTION AND I NSTALLATION
This chapter contains information on initial inspection, bench use and rack mounting instructions. It also
contains the initial adjustments necessary to start operations.
C
HAPTER 2 S PECIFICATIONS
This Chapter lists all the specification applicable to this model.
C
HAPTER 3 G ETTING S TARTED
This chapter covers the fundamentals of ohmmeter operation. It shows you how to use the ohmmeter's
front & rear panel, how to make connections, and describes the display sections and messages.
C
HAPTER 4 M EASUREMENT M ODES & F UNCTIONS
This chapter explains how to setup the instrument for all standard measurements, temperature
compensated measurements and hi-lo comparison. Also contains information and procedures on how
to configure the settings.
C
HAPTER 5 O PTIONAL F EATURES AND A CCESSORIES
This chapter lists and describes all the optional equipment and accessories available for this model.
C
HAPTER 6 R EMOTE I NTERFACE
This chapter illustrates the remote capabilities and explains how to send commands to the ohmmeter
from remote, and how to retrieve data from remote.
C
HAPTER 7 BCD I NTERFACE
This chapter illustrates the remote capabilities and explains how to send commands to the ohmmeter
from remote, and how to retrieve data from remote.
C
HAPTER 8 R OUTINE M AINTENANCE
This chapter illustrates how to perform routine maintenance to the ohmmeter. It covers the calibration
procedures and fuse replacement.
C
HAPTER 9 S PECIAL P ROCEDURES
This chapter contains a number of useful tips that should be noted when working with inductive loads.
C
HAPTER 10 T HEORY OF O PERATION
This chapter describes the theory of operation of the ohmmeter and its features. It gives a detailed
circuit description and troubleshooting information.
C
HAPTER 11 A DDENDUMS
This chapter lists updates and addendums for this manual.
C HAPTER 12 P ARTS L IST
This chapter lists all the parts and components used in the manufacturing of the ohmmeter.
C
HAPTER 13 D RAWINGS AND S CHEMATICS
This chapter contains all the assembly drawings and schematics for the ohmmeter.

1
. TABLE OF CONTENTS
CHAPTER 1 INSPECTION AND INSTALLATION.......................................................................... 4
1.1 I NTRODUCTION ............................................................................................................................. 4
1.2 I NSPECTION .................................................................................................................................. 4
1.3 L INE V OLTAGE /F USE S ELECTION ................................................................................................. 4
1.4 B ENCH U SE .................................................................................................................................. 5
1.5 R ACK M OUNTING ......................................................................................................................... 5
1.6 S AFETY P RECAUTIONS ................................................................................................................. 6
CHAPTER 2 SPECIFICATIONS ......................................................................................................... 7
2.1 S TANDARD M EASUREMENT M ODE S PECIFICATIONS .................................................................... 7
2.2 T EMPERATURE C OMPENSATOR M ODE S PECIFICATIONS ............................................................... 8
2.3 G ENERAL S PECIFICATIONS ........................................................................................................... 9
2.4 E NVIRONMENTAL AND P OWER R EQUIREMENTS ........................................................................... 9
2.5 P HYSICAL S PECIFICATIONS .......................................................................................................... 9
CHAPTER 3 GETTING STARTED................................................................................................... 10
3.1 I NTRODUCTION ........................................................................................................................... 10
3.2 F RONT P ANEL ............................................................................................................................ 10
3.2.1 Power Switch ........................................................................................................................ 10
3.2.2 Display.................................................................................................................................. 11
3.2.3 Range Selection Keys............................................................................................................11
3.2.4 Function/Numerical Keys ..................................................................................................... 12
3.2.5 TCM Receptacle and LEDs .................................................................................................. 13
3.2.6 HLC LEDs ............................................................................................................................ 14
3.2.7 Remote LED.......................................................................................................................... 14
3.2.8 Source and Sense Binding Post ............................................................................................ 14
3.3 R EAR P ANEL .............................................................................................................................. 15
3.3.1 Line Voltage Switch .............................................................................................................. 15
3.3.2 Fuse Holder .......................................................................................................................... 16
3.3.3 Power Connector.................................................................................................................. 16
3.3.4 HLC Relay Terminal............................................................................................................. 16
3.3.5 RS-232 Connector................................................................................................................. 17
3.4 A PPLYING P OWER ...................................................................................................................... 18
3.4.1 Power-On Default Settings................................................................................................... 18
3.5 C ONNECTING A L OAD TO THE 4176............................................................................................ 19
3.6 R ANGE S ELECTION ..................................................................................................................... 21
3.7 O VERLOAD AND S AFE M ODE ..................................................................................................... 21
CHAPTER 4 MEASUREMENTS MODES AND FUNCTIONS...................................................... 22
4.1 S TANDARD M EASUREMENT M ODE ............................................................................................. 22
4.2 “TCM” - T EMPERATURE C OMPENSATED M EASUREMENT M ODE ............................................... 23
4.2.1 Omni Compensator............................................................................................................... 24
4.2.2 TCM ON ............................................................................................................................... 24
4.2.3 TCS – Temperature Compensator Setup .............................................................................. 24
4.2.4 TCC – Temperature Compensator Calibration .................................................................... 27
4.3 “HLC” - H I -L O C OMPARATOR M ODE ........................................................................................ 28
4.3.1 HLC Relay Terminal............................................................................................................. 28
4.3.2 Setting the Limits .................................................................................................................. 29
4.3.3 HLC ON................................................................................................................................ 30
4.4 U PDATE F UNCTION .................................................................................................................... 31

2
4.4.1 Setting the Display Update Rate and Intensity ..................................................................... 31
4.5 R UN /H OLD F UNCTION ................................................................................................................ 32
4.5.1 Configuring the Run/Hold Function..................................................................................... 33
4.6 P RINT /L OG F UNCTION ................................................................................................................ 34
4.6.1 Configuring the Print/Log Function..................................................................................... 35
4.7 V IEW F UNCTION ......................................................................................................................... 36
4.7.1 Using the View function........................................................................................................ 36
CHAPTER 5 OPTIONAL FEATURES AND ACCESSORIES ....................................................... 39
5.1 O PTIONS ..................................................................................................................................... 39
5.1.1 BCD: Data Output................................................................................................................ 39
5.1.2 GPIB..................................................................................................................................... 39
5.1.3 USB....................................................................................................................................... 39
5.2 A CCESSORIES ............................................................................................................................. 40
5.2.1 Omni Compensator............................................................................................................... 40
5.2.2 Option R: Rack Mount Adapter ........................................................................................... 40
5.3 T EST L EADS ............................................................................................................................... 41
5.3.1 Alligator Clip Type Leads..................................................................................................... 41
5.3.2 Needle Type Probes.............................................................................................................. 42
5.3.3 Surface Probes...................................................................................................................... 43
5.3.4 Other Lead Sets .................................................................................................................... 44
CHAPTER 6 REMOTE INTERFACE ............................................................................................... 45
6.1 INTRODUCTION..................................................................................................................... 45
6.2 CONNECTING THE 4176 VIA GPIB INTERFACE ............................................................... 45
6.2.1 The GPIB interface capabilities:.......................................................................................... 45
6.2.2 Notes for GPIB installation .................................................................................................. 46
6.2.3 Computer’s Connection........................................................................................................ 46
6.2.4 The GPIB connection testing................................................................................................ 46
6.3 CONNECTING THE 4176 VIA RS232 INTERFACE.............................................................. 47
6.3.1 The RS232 interface capabilities:......................................................................................... 47
6.3.2 Notes for RS232 installation................................................................................................. 47
6.3.3 Connecting to a Computer.................................................................................................... 49
6.3.4 Checking Connections .......................................................................................................... 49
6.4 INPUT AND OUTPUT QUEUE............................................................................................... 50
6.5 COMMANDS AND SYNTAX ................................................................................................. 50
6.5.1 RS232 message terminators.................................................................................................. 50
6.5.2 Entering Commands ............................................................................................................. 50
6.5.3 Command Characters........................................................................................................... 50
6.5.4 Combining Commands ......................................................................................................... 50
6.5.5 Synopsis of Commands ......................................................................................................... 51
6.6 DETAILS OF COMMAND REFERENCE............................................................................... 51
6.6.1 Command Index.................................................................................................................... 51
CHAPTER 7 BCD INTERFACE ........................................................................................................ 66
7.1 G ENERAL ................................................................................................................................... 66
7.2 BCD P IN A SSIGNMENTS ............................................................................................................. 66
CHAPTER 8 ROUTINE MAINTENANCE ....................................................................................... 69
8.1 G ENERAL ................................................................................................................................... 69
8.2 R EQUIRED T EST E QUIPMENT ...................................................................................................... 69
8.3 P RE -C ALIBRATION P ROCEDURE ................................................................................................. 69
8.4 4176 C ALIBRATION P ROCEDURE ................................................................................................ 70
8.4.1 Standard Calibration............................................................................................................ 70
8.4.2 Periodic Maintenance........................................................................................................... 75

3
CHAPTER 9 SPECIAL PROCEDURES............................................................................................ 76
9.1 N OISY R EADINGS ....................................................................................................................... 76
9.2 I NDUCTIVE L OADS ..................................................................................................................... 76
CHAPTER 10 THEORY OF OPERATION.................................................................................... 77
10.1 L OCALIZING THE P ROBLEM ........................................................................................................ 77
10.2 C OMPONENT R EPLACEMENT ...................................................................................................... 77
10.3 G ENERAL C IRCUIT D ESCRIPTIONS .............................................................................................. 78
10.4 T ROUBLESHOOTING ................................................................................................................... 79
10.5 C URRENT S OURCE D ETAILED C IRCUIT D ESCRIPTIONS ............................................................... 80
10.5.1 Power Supplies ................................................................................................................ 80
10.5.2 Constant-Current Source................................................................................................. 81
10.6 M ICRO -C ONTROLLER B OARD D ETAILED C IRCUIT D ESCRIPTIONS .............................................. 82
10.6.1 Micro-Controller ............................................................................................................. 82
10.6.2 Over-Voltage Protection.................................................................................................. 82
10.6.3 TCM................................................................................................................................. 83
10.6.4 Reset................................................................................................................................. 83
10.6.5 2.5V Reference................................................................................................................. 83
10.6.6 Download/Normal Switch................................................................................................ 83
10.6.7 RS-232/Display Switch and RS 232 Driver/Receiver....................................................... 83
CHAPTER 11 ADDENDUMS........................................................................................................... 84
CHAPTER 12 PARTS LIST ............................................................................................................. 85
CHAPTER 13 DRAWINGS AND SCHEMATICS......................................................................... 94

4
Chapter 1 . INSPECTION AND INSTALLATION
1.1 Introduction
Welcome to the world of low resistance measurement! The precision instrument you have
just purchased offers super-stable measurement capability for hard-to-test items such as
transformers, coils, shunts, and even the resistance of wire itself. Other features include
temperature compensation, hi-lo comparison and several interface options.
Please read this manual thoroughly and all accompanying addendums before attempting to
operate this ohmmeter.
1.2 Inspection
If the shipping carton is damaged, request that the carrier's agent be present when the unit is
unpacked. If the instrument appears damaged, the carrier's agent should authorize repairs
before the unit is returned to the factory. Even if the instrument appears undamaged, it may
have suffered internal damage in transit that may not be evident until the unit is operated or
tested to verify conformance with its specifications. If the unit fails to operate or fails to
meet the performance specifications of chapter 2, notify the carrier's agent and the nearest
Valhalla Sales Office. Retain the shipping carton for the carrier's inspection. DO NOT
return equipment to Valhalla Scientific, Inc. or any of its sales offices prior to obtaining
authorization to do so.
1.3 Line Voltage/Fuse Selection
The only adjustments required before placing the unit in operation are:
1. Verify that the instrument has been set for the proper local AC line voltage.
The AC line voltage is selected via a sliding switch mounted on the rear
panel of the ohmmeter.
Table 1 – Line Voltage Limits
Nominal Value (RMS) Allowable Limits (RMS)
115V 105Vac to 125Vac
230 210Vac to 250Vac

5
Figure 1 – 4176 Rear Panel
Figure 2 – Line Voltage Switch Position
2. Verify that the proper fuse for this voltage has been installed as follows:
FuseBloSloAmpVac
FuseBloSloAmpVac
−=
−
=
125.0230
250.0115
1.4 Bench Use
The ohmmeter is supplied with all the hardware required for bench use and special
instructions for use in this manner are not necessary. The user should become familiar with
chapters 3 and 4 before attempting to operate the instrument.
1.5 Rack Mounting
Optional brackets are available for mounting the ohmmeter in a standard 19" equipment
rack. The rack mount kit consists of two brackets plus 4 flat head screws. The brackets are
easily installed on the front end of each side rail as show in drawing № 4176-xxx in chapter
11. The kit is listed in chapter 5 as Option-R
The size of the ohmmeter and the location of its center of gravity dictate that it must be
supported on both sides along its entire length through the use of trays or slides. If it is to be
transported while mounted in a rack, it should be supported so as to prevent upward or
downward movement.
It is recommended that blank panels at least 1.75 inches high be installed between this and
any other units in the rack to ensure freedom of air flow. Under no circumstances should the
ambient air temperature around the unit exceed 50°C while the unit is in operation or 70°C
when power is removed.

6
1.6 Safety Precautions
The power plug must be a three-contact device and should be inserted only into a three-
contact mating socket where the third contact provides a ground connection. If power is
provided through an extension cable, the ground connection must be continuous. Any
discontinuity in the ground lead may render the unit unsafe for use!
The testing of inductive loads such as transformers requires that special precautions be taken
to avoid damage to the instrument and/or injury to the operator! Please refer to chapter 7.

7
Chapter 2 . SPECIFICATIONS
The specifications for the 4176 Programmable µ-Ohmmeter are listed in the following
paragraphs. In all cases the specifications are valid for full Kelvin Four-Terminal
measurements using connections having less than 20mΩ of lead resistance per wire.
2.1 Standard Measurement Mode Specifications
Table 2 – Range Characteristics
Range Full Scale Maximum
Resolution
Current
Source
1
20mΩ 20.000mΩ 1µΩ 1A
.2Ω .30000Ω 10µΩ 1A
2Ω 3.0000Ω 100µΩ 100mA
20Ω 30.000Ω 1mΩ 10mA
200Ω 300.00Ω 10mΩ 1mA
2kΩ 3.0000kΩ 100mΩ 100µA
20kΩ 30.000kΩ 1Ω 10µA
1
Current source is ±1%
absolute accuracy.
Table 3 – Standard Measurement Mode Accuracy
Accuracy
2
(± % of reading ± % of range)
Range 24 hours 1 Year
Temperature
Coefficient
3
20mΩ ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
.2Ω ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
2Ω ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
20Ω ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
200Ω ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
2kΩ ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
20kΩ ±0.006 ± 0.012 ±0.02 ± 0.02 ±0.002%/°C
2
The accuracy
specifications listed are
valid following a 30 minute
warm-up at an ambient
temperature between 15°C
and 35°C, and include the
effects of line voltage
variations within the
allowed range.
3
Temperature coefficient
specified for temperature
ranges from 0°C to 15°C
and 35°C to 50°C.

8
Figure 3 - 20mΩ Range Error Graph Figure 4 - 200mΩ to 20kΩ Range Error
Graph
2.2 Temperature Compensator Mode Specifications
Table 4 – Temperature Compensator Mode Specifications
Accuracy
4
Range T
5
<25°C
(± % of reading ± % of range ± % of
T
5
>25°C
(± % of reading ± % of range ± % of
20mΩ ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
.2Ω ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
2Ω ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
20Ω ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
200Ω ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
2kΩ ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
20kΩ ±0.02 ± 0.07 ± 0.001 ±0.02 ± 0.07 ± 0.001
4
The accuracy
specifications listed are
valid following a 30
minute warm-up at an
ambient temperature
between 15°C and
35°C, and include the
effects of line voltage
variations within the
allowed range.
5
T indicates the
temperature in °C of the
test area.
0.01
0.1
1
10
110 100
% of Full Scale
Max % of Error
0.01
0.1
1
10
1 10 100
% of Full Scale
Max % of Error

9
2.3 General Specifications
Display Type: .......................................................................................................................5 digits VFD
A-to-D Conversion Rate:................................................................................... 45 conversions/seconds
Display Update:.........................5 user selections (100msec, 200msec, 300msec, 400msec, 500msec)
Overload:
20mΩ Range ............................................................................................................ 99.95% of range
200mΩ thru 20kΩ................................................................................................. 119.95% of range
Overload Indication: .........................................................................................flashes “OVERLOAD”
6
Terminal Configuration: ...............................................................................................Four-wire Kelvin
Test Current Polarity: ................................................................................Positive (flows High to Low)
Test Current Compliance Voltage:..................................................................................... 5V minimum
Settling Time:................................................................................................................ 300 milliseconds
2.4 Environmental and Power Requirements
Power Supply: ......................................... 115VAC or 230VAC ±10% @ 50Hz to 400Hz; 25VA max
Operating Temperature Range: ............................................................................................ 0°C to 50°C
Storage Temperature Range: .......................................................................................... -40°C to +85°C
2.5 Physical Specifications
Humidity:............................................................................... 80% RH max. @ 40°C (non-condensing)
Dimensions:.................................................................17"(43cm) W x 11½"(29.5cm) D x 4"(10cm) H
Weights:........................................................................ 10.36lbs (4.7kg) NET; 15lbs (7kg) SHIPPING
6
If the overload indication is on for approximately 10 seconds, the instrument will enter Safe Mode. See
section 7 of chapter 3 for details.

10
Chapter 3 . GETTING STARTED
3.1 Introduction
This chapter covers the fundamentals of ohmmeter operation. It shows how to use the
ohmmeter's front & rear panel, how to make connections, and describes the display
sections and messages.
Before explaining how to make measurements, it is useful to describe the sections of the
front and rear panel of the 4176.
3.2 Front Panel
The front panel of the 4176 can be broken down into eight parts. In Figure 5 you can see
the regions indicated by their name.
Figure 5 - 4176 Front Panel Sections
3.2.1 Power Switch
The power switch is a two position ON/OFF rocking switch, used to apply (ON position)
or disconnect (OFF position) the AC power source from the internal circuitry of the
ohmmeter.

11
3.2.2 Display
During measurements, the display presents 3 windows described in the table below.
Window Description
Measurement Window Displays the measured load value or the temperature compensated value.
Range Window Displays the selected range or the auto range function is on, this section of the display will
alternate between the automatically selected range and the word “AUTO”.
Function Window Displays the Valhalla Scientific Logo. If a function is activated, this section of the display will
alternate between the Logo and the abbreviated function name.
Figure 6 – Display Window sections
The display is also used to prompt the user with alerts and messages
3.2.3 Range Selection Keys
The seven range keys simply allow the user to select the required measurement range of
the ohmmeter. The range keys are labeled with the respective range value and current
source value.
Figure 7 - Range Keys
Extra care must be taken when working with inductive loads.
Always select the highest resistance range before connecting or
disconnecting the test leads.

12
3.2.4 Function/Numerical Keys
The Function/Numerical keys are sixteen and are used to trigger the standard and/or
optional ohmmeter functions and for data entry. In figure 8 shows the key arrangement
while table 5 lists a brief description of the keys and its use. The Function/Numerical
keys will be further described throughout this manual.
Figure 8 - Function/Numerical Keys
Table 5 - Function/Numerical Key Description
Key Function Description Numerical Value
F UNC . The F
UNC . key is used in combination with other keys to change stored settings.
This key is also used as a “Forward” button to skip through screens. none
V IEW The V
IEW key is used in combination with other function keys. It is used to view
stored settings. 0
U PDATE The U
PDATE key is used to set and/or view display update rate and intensity. 1
HLC The HLC key is used to enable or disable the 4176’s internal “Multi-Range Dual
Limit Comparator. Also used to set and/or view the limits used. 2
A DDR . The A
DDR . key is used to view the setting information for all of the standard or
optional remote interfaces. 3
R UN /H OLD The R
UN /H OLD key is used to switch between run and hold state. Also used to
select the hold configuration. 4
P RINT The P
RINT key is used to trigger the output of a print or log package to the RS-
232 port. Also used to select the print/log setting. 5
TCM The TCM key is used to enable or disable the TCM mode. Also used to select
temp. coefficient and reference, and for TC calibration. 6
A UTO R NG The A
UTO R NG key enables the automatic selection of the range according to the
value of the load. 7
C AL The C
AL key is used to initiate the standard and TCM calibration procedure. 8
BCD The BCD key enables the binary coded decimal output on models where the
BCD option is installed. 9
C LEAR The C
LEAR key functions like a backspace when entering values. The key is also
used to return to the previous screen. none
R ESET The R
ESET key resets the ohmmeter returning it to Start-Up state. none
L OCAL The L
OCAL key is used to return from a remote to a local state. none
E NTER The E
NTER key is the user confirmation to a display prompt. none
m/k The m/k key is used to toggle between polarity symbols where active. ./±

13
3.2.5 TCM Receptacle and LEDs
This portion of the front panel is utilized only during temperature compensated type
measurements (TCM). TCM mode is described in detail in chapter 4 section 2.
Critical to this measurement mode is precise temperature sensing, which entails solid and
reliable connections between the sensing device and the instrument. The temperature
sensor receptacle is designed so that the mating connector/sensor, the Valhalla Scientific
Omni Compensator
7
, can be inserted only in the proper mating position. A red dot on
the Omni Compensator and a red tab on the receptacle are met to guide you in the
insertion of the connector in the receptacle.
Figure 9 - Temperature sensor, TCM LEDs and Receptacle
The TCM feature of the 4176, arithmetically calculates the resistance value to display
utilizing the ambient temperature and other parameters that will be present in later
chapters. It is solemn for the user to be aware if the TCM mode is enabled or disabled so
that the display reading may be interpreted correctly.
The green LED labeled “T.C.Mode”, is the visual indication that the TCM mode is on.
Keeping an eye on the red LED, labeled “Fault”, also as important. “Fault” is the
indicator that alerts of missing contacts between the sensor and the instrument.
Values displayed while the fault indicator is illuminated are not to be
considered valid in any case.
7
The Omni Compensator is an optional accessory to the 4176. See chapter 5 section 2.1 for more detail.

14
3.2.6 HLC LEDs
This portion of the front panel is designated to give the
user a visual indication of the HLC results. HLC mode
is described in detail in chapter 4 section 3. The HLC
LEDs are active only when the Hi-Lo comparator mode
(HLC) is activated. The green LED, labeled “GO”, is
on if the measured resistance value is between the
limits
8
set by the user. The yellow LED, labeled
“ExceedLO”, is on if the measured resistance value is less then the lower limit. The red
LED, labeled “ExceedHI”, is on if the measured resistance value is greater then the upper
limit. Only one LED can be on at a time; if more then one LED is on for any length of
time, it is recommended that you contact the Valhalla Scientific Tech Support Team.
3.2.7 Remote LED
The Remote Led indicates the remote/local state of the instrument. If the LED
is on, the instrument is in remote state and can only receive commands
through one of its remote interface ports. If the LED is off, the ohmmeter is in
local state will receive commands only from the front panel keys.
3.2.8 Source and Sense Binding Post
Connections to the 4176 are made via the front
panel source/sense terminals, which consist of
two red and two black standard binding posts
with gold plated brass contact material. The
posts can accept standard banana plugs, wires
up to 12 AWG, or spade lugs. The four
terminals provide full 4-Wire Kelvin
measurement capability. The right posts are the
positive and negative current source terminals
and provide the test current, while the left posts
are the positive and negative voltage sense terminals used to monitor the voltage drop
across the load.
The 4-Wire configuration eliminates errors normally caused by test lead and contact
resistances. In many applications the contact resistance can exceed the value of the load by
several orders of magnitude. The 4176 bypasses this potential error source by providing two
terminals of constant current and an additional two terminals for high impedance voltage
sensing. The result is a fast, accurate resistance measurement of the load, independent of the
8
See chapter 4 section 3.2 for detail on how to set the Hi-Lo limits.