Valhalla Scientific 4300C User manual

4300C
Programmable Micro-Ohmmeter
Revision 64.1

1
VALHALLA SCIENTIFIC INC. CERTIFICATION
Valhalla Scientific, Inc. certifies that this instrument was thoroughly tested and 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 Nation Institute of Standards and
Technology to the extent allowed by NIST’s calibration facility.
Due to continuing product refinement and due to possible parts manufacturer changes, Valhalla
Scientific, Inc. reserve the rights to change any or all specifications without notice.
VALHALLA SCIENTIFIC INC. WARRANTY STATEMENT
The warranty period for this instrument is stated on your invoice and packing list. Please refer to these
to determine appropriate warranty dates.
We will repair the instrument during the warranty period provided it is returned to Valhalla Scientific,
Inc. 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.
Due to continuing product refinement and due to possible parts manufacturer change, Valhalla
Scientific reserves the right to change any or all specifications without notice.
SUPPORT
For repair and calibration services, call 800-548-9806 or visit valhallascientific.com.
Email support available at [email protected]
4300C Programmable Digital Micro-Ohmmeter User Manual
Revision 64-1 (2021)
Copyright © 2021 Valhalla Scientific, Inc. All rights reserved.

2
WARNINGS
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 greater 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.

3
Table of Contents
General Information .................................................................................................................................... 7
Instrument Description ............................................................................................................................ 7
Instrument Identification ......................................................................................................................... 7
Safety Precautions ................................................................................................................................... 7
Unpacking and Installing .............................................................................................................................. 8
Inspection ................................................................................................................................................ 8
Setting the Line Voltage ........................................................................................................................... 8
Fuse Selection .......................................................................................................................................... 8
Rack Mounting ......................................................................................................................................... 9
Specifications ............................................................................................................................................. 10
Standard Measurement Mode Specifications ....................................................................................... 10
Temperature Compensator Mode Specifications .................................................................................. 11
General Specifications ........................................................................................................................... 11
Environmental ....................................................................................................................................... 11
Power Requirements ............................................................................................................................. 11
Physical .................................................................................................................................................. 11
Getting Started .......................................................................................................................................... 12
4-Wire Configuration ............................................................................................................................. 12
Front Panel ............................................................................................................................................ 13
On/Off Switch .................................................................................................................................... 13
Display ............................................................................................................................................... 13
Range Selection and Test Current Key ............................................................................................... 14
Function/Numerical Keys ................................................................................................................... 14
TC Mode Key and Sensor Receptacle ................................................................................................. 16
HLC LEDs ............................................................................................................................................ 16
Cable Disconnect Status Indicators .................................................................................................... 16
Charging Inductor Mode .................................................................................................................... 17
Source and Sense Binding Post .......................................................................................................... 17
Rear Panel .............................................................................................................................................. 18
Line Voltage Switch ............................................................................................................................ 18
Fuse Holder ........................................................................................................................................ 18
Power Connector ............................................................................................................................... 19

4
HLC Relay Terminal ............................................................................................................................ 19
RS-232 Connector .............................................................................................................................. 19
Applying Power ...................................................................................................................................... 20
Power-On Default Settings .................................................................................................................... 20
Connecting a Load to the 4300C ............................................................................................................ 21
Taking Standard Measurements ............................................................................................................ 23
Setting the Range ............................................................................................................................... 23
Test Current ....................................................................................................................................... 23
Charging Inductor Mode .................................................................................................................... 24
Cable Disconnect Status Indicators .................................................................................................... 24
Measurement Modes and Functions ......................................................................................................... 25
Standard Measurement Mode .............................................................................................................. 25
“TCM” - Temperature Compensated Measurement Mode ................................................................... 25
Omni Compensator ............................................................................................................................ 26
TCM ON ............................................................................................................................................. 26
TCS – Temperature Compensator Setup ........................................................................................... 27
TCC – Temperature Compensator Calibration ................................................................................... 28
“HLC” – Hi-Lo Comparator Mode ........................................................................................................... 29
HLC Relay Terminal ............................................................................................................................ 29
Setting the Limits ............................................................................................................................... 30
HLC ON ............................................................................................................................................... 31
Update Function .................................................................................................................................... 31
Display Update Rate .......................................................................................................................... 31
Display Intensity ................................................................................................................................ 32
Setting the Display Update Rate and Intensity .................................................................................. 32
Run/Hold Function ................................................................................................................................. 33
RUN/HOLD ......................................................................................................................................... 33
RUN/PKHI ........................................................................................................................................... 33
RUN/PKLO .......................................................................................................................................... 33
Configuring the Run/Hold Function ................................................................................................... 33
Print/Log Function ................................................................................................................................. 34
PRINT ................................................................................................................................................. 34
LOG .................................................................................................................................................... 34

5
LOG2 .................................................................................................................................................. 34
Configuring the Print button function ............................................................................................... 34
View Function ........................................................................................................................................ 35
Using the View function ..................................................................................................................... 35
Optional Features and Accessories ............................................................................................................ 36
Options .................................................................................................................................................. 36
GPIB ................................................................................................................................................... 36
USB .................................................................................................................................................... 36
CET ..................................................................................................................................................... 36
Accessories ............................................................................................................................................ 37
Omni Compensator ............................................................................................................................ 37
Option RX-3: Rack Mount Adapter .................................................................................................... 37
Test Leads .............................................................................................................................................. 37
Alligator Clip Type Leads .................................................................................................................... 37
Needle Type Probes ........................................................................................................................... 38
Surface Probes ................................................................................................................................... 38
Other Lead Sets .................................................................................................................................. 38
Remote Operations ................................................................................................................................... 39
IEEE Interface ......................................................................................................................................... 39
Definitions ............................................................................................................................................. 39
Bus Restrictions ..................................................................................................................................... 40
Detailed Descriptions of Bus Operations ............................................................................................... 41
Setting the IEEE Address ........................................................................................................................ 43
Remote and Local States ....................................................................................................................... 44
Local State ......................................................................................................................................... 44
Remote State ..................................................................................................................................... 44
Reading the Display Data ....................................................................................................................... 44
4300C Command Set for GPIB ............................................................................................................... 45
Voltage Range .................................................................................................................................... 46
Test Current Range ............................................................................................................................ 46
SRQ's and Serial Polls ......................................................................................................................... 46
Output Data Terminator .................................................................................................................... 47
Test Current Control .......................................................................................................................... 47

6
Display Hold ....................................................................................................................................... 47
Temperature Compensation .............................................................................................................. 47
Configuration Status Query ............................................................................................................... 48
RS-232 Interface .................................................................................................................................... 50
The RS232 interface capabilities: ....................................................................................................... 50
Notes for RS232 installation .............................................................................................................. 50
Connecting to a Computer ................................................................................................................. 51
Checking Connections ........................................................................................................................ 51
INPUT AND OUTPUT QUEUE .................................................................................................................. 51
COMMANDS AND SYNTAX ..................................................................................................................... 51
RS232 message terminators .............................................................................................................. 51
Entering Commands .......................................................................................................................... 51
Command Characters ........................................................................................................................ 51
Combining Commands ....................................................................................................................... 52
Synopsis of Commands ...................................................................................................................... 52
DETAILS OF COMMAND REFERENCE ..................................................................................................... 52
COMMAND INDEX ................................................................................................................................. 52
Routine Maintenance ................................................................................................................................ 67
General .................................................................................................................................................. 67
Required Test Equipment ...................................................................................................................... 67
Pre-Calibration Procedure ..................................................................................................................... 67
4300C Calibration Procedure ................................................................................................................. 68
Standard Calibration .......................................................................................................................... 68
Sense Calibration ............................................................................................................................... 68
Current Source Calibration ................................................................................................................ 70
TCM Calibration ................................................................................................................................. 71
Special Procedures ..................................................................................................................................... 73
General .................................................................................................................................................. 73
Connections and Settling Time .............................................................................................................. 73
Noisy Readings ....................................................................................................................................... 74
Disconnecting the Cables ....................................................................................................................... 75
Addendums ................................................................................................................................................ 77

7
General Information
Instrument Description
The Model 4300C is a unique instrument capable of handling even the toughest resistance measurement
applications. The 4300C is designed to measure the low resistance of such items as coils, transformers,
ballasts, heater elements, etc. Some features of the 4300C that give it an edge over competitive products
are:
• "Charging Inductor" mode for reduced settling times.
• "Disconnect Status" indicators designed with safety in mind.
• Full 4-wire Kelvin terminal configuration.
• Fully selectable test currents up to 10A.
• Temperature Compensation.
• Internal Hi-Lo Limit Comparator.
• Available locking rear Bendix connectors.
• Data outputs and remote programming capability.
Please read this manual thoroughly and all accompanying addendums before attempting to operate this
ohmmeter.
Instrument Identification
Valhalla Scientific instruments are identified by a two-part serial number. The Serial Tag is located on the
rear or bottom of the instrument. The number is in a form of 64-0000. The first two digits, called the serial
number prefix, indicate the model. It changes only when a change is made to the instrument. The last 4
digits, called the serial number suffix, are unique for each individual unit.
Be sure to include the entire serial number, both prefix and suffix, in any correspondence about your
instrument.
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 Model 4300C utilizes forced air cooling of the internal components. This operates continuously and
care must be taken to ensure that the intake and exhaust ports remain clear. Blocked vents may cause a
dangerous overheating condition!

8
Unpacking and Installing
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, 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.
Setting the Line Voltage
The line voltage selection is preconfigured according to the country to which it is shipped or as specified
by the customer.
To change this setting, follow the steps below:
1. Remove the power cord from the instrument.
2. With a small flat head screwdriver, slide the “Line Voltage Selector” switch to the appropriate
position.
3. Replace the line power fuse accordingly.
Fuse Selection
The line power fuse must match the line voltage selection as follows:
• 105-125VAC – 3A SLO-BLO
• 210-250VAC – 1.5A SLO-BLO
The fuse holder is located on the rear panel. To install a fuse, first disconnect the Ohmmeter’s power cord.
Insert one end of the fuse into the fuse cap. Insert the fuse cap into the fuse holder. With a small flathead
screwdriver, push in on the fuse cap and rotate it clockwise.

9
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 (see Figure 1). The kit is listed under accessories as RX-3
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 using trays or slides. If it is to be transported while mounted in a rack, it
should be supported 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.
Figure 1 – Rack Mount Adapter RX-3

10
Specifications
This section contains accuracy and operational specifications for the Model 4300C. The accuracy
specifications are valid for a period of one year from the date of calibration at a temperature of 22°C to
28°C. Outside this range, the temperature coefficient specification applies.
Standard Measurement Mode Specifications
#
Range
Test
Voltage
Full Scale
Resolution
Current
Source1
Accuracy2
(±% of Reading ±Ω)
Temperature
Coefficient3
1
2mΩ
20mV
2.0000mΩ
100nΩ
10A
±0.06 ±0.0006m
±50ppm/°C
2
20mΩ
20mV
20.000mΩ
1µΩ
1A
±0.04 ±0.006m
±50ppm/°C
3
200mΩ
20mV
200.00mΩ
10µΩ
.1A
±0.04 ±0.06m
±50ppm/°C
4
2Ω
20mV
2.0000Ω
100µΩ
10mA
±0.04 ±0.0006
±50ppm/°C
5
20Ω
20mV
20.000Ω
1mΩ
1mA
±0.04 ±0.006m
±50ppm/°C
6
200Ω
20mV
200.00Ω
10mΩ
0.1mA
±0.04 ±0.06m
±50ppm/°C
7
20mΩ
200mV
20.000mΩ
1µΩ
10A
±0.06 ±0.003m
±50ppm/°C
8
200mΩ
200mV
200.00mΩ
10µΩ
1A
±0.04 ±0.03m
±50ppm/°C
9
2Ω
200mV
2.0000Ω
100µΩ
.1A
±0.04 ±0.0003
±50ppm/°C
10
20Ω
200mV
20.000Ω
1mΩ
10mA
±0.04 ±0.003
±50ppm/°C
11
200Ω
200mV
200.00Ω
10mΩ
1mA
±0.04 ±0.03
±50ppm/°C
12
2kΩ
200mV
2.0000kΩ
100mΩ
0.1mA
±0.04 ±0.0003k
±50ppm/°C
13
200mΩ
2V
200.00mΩ
10µΩ
10A
±0.06 ±0.03m
±50ppm/°C
14
2Ω
2V
2.0000Ω
100µΩ
1A
±0.04 ±0.0003
±50ppm/°C
15
20Ω
2V
20.000Ω
1mΩ
.1A
±0.04 ±0.003
±50ppm/°C
16
200Ω
2V
200.00Ω
10mΩ
10mA
±0.04 ±0.03
±50ppm/°C
17
2kΩ
2V
2.0000kΩ
100mΩ
1mA
±0.04 ±0.0003k
±50ppm/°C
18
20kΩ
2V
20.000kΩ
1Ω
0.1mA
±0.04 ±0.003k
±50ppm/°C
Table 1 - Ranges Parameters and Accuracies
1
Current Source is ±1% absolute accuracy.
2
Accuracy specifications are valid following a 30-minute warm-up at an ambient temperature between 22°C and
28°C and include the effects of line voltage variations within the allowed range.
3
Temperature coefficient Specified for temperature ranges from 5°C to 21°C and 29°C to 50°C.

11
Temperature Compensator Mode Specifications
#
Range
Range Setting
Accuracy4
1
2mΩ
10A/20mV
±0.11 of reading ±0.0006mΩ
2
20mΩ
1A/20mV
±0.09 of reading ±0.006mΩ
3
200mΩ
.1A/20mV
±0.09 of reading ±0.06mΩ
4
2Ω
10mA/20mV
±0.09 of reading ±0.0006Ω
5
20Ω
1mA/20mV
±0.09 of reading ±0.006mΩ
6
200Ω
0.1mA/20mV
±0.09 of reading ±0.06mΩ
7
20mΩ
10A/200mV
±0.11 of reading ±0.003mΩ
8
200mΩ
1A/200mV
±0.09 of reading ±0.03mΩ
9
2Ω
.1A/200mV
±0.09 of reading ±0.0003Ω
10
20Ω
10mA/200mV
±0.09 of reading ±0.003Ω
11
200Ω
1mA/200mV
±0.09 of reading ±0.03Ω
12
2kΩ
0.1mA/200mV
±0.09 of reading ±0.0003kΩ
13
200mΩ
10A/2V
±0.11 of reading ±0.03mΩ
14
2Ω
1A/2V
±0.09 of reading ±0.0003Ω
15
20Ω
.1A/2V
±0.09 of reading ±0.003Ω
16
200Ω
10mA/2V
±0.09 of reading ±0.03Ω
17
2kΩ
1mA/2V
±0.09 of reading ±0.0003kΩ
18
20kΩ
0.1mA/2V
±0.09 of reading ±0.003kΩ
Table 2 - Temperature Compensation Mode Specifications
General Specifications
Display: .................................................................................................................... Multi Section VFD 140px x 32px
Overload Indication: ..................................................................................................... Display flashes “OVERLOAD”
Terminal Configuration: ................................................................................................................... Four-wire Kelvin
ADC Conversion Rate: .......................................................................................................... 45 conversions / second
Display Update: .............................................. 5 user selections (100msec, 200msec, 300msec, 400msec, 500msec)
Maximum Kick-Back Protection: ..................................................................................... 500A Peak Induced Current
Compliance Voltage (Normal Mode): .................................................................... 7.5 VDC nominal at 10A resistive
Compliance Voltage (Charging Inductor Mode): ......................................................... > 20 VDC when indicator is lit
Open Circuit Voltage (Test Current Off): ....................................................... < 20mV between IHI and ILO terminals
Environmental
Operating Temperature Range: ................................................................................................................... 0 to 50°C
Humidity: ................................................................................................................ 70% RH at 40°C non-condensing
Storage Temperature Range: .................................................................................................................. -30°C to 70°
Power Requirements
Power Supply Voltage: ........................................................................................................ 105-125 or 210-250 VAC
Power Supply Frequency: ........................................................................................................................... 50 - 60 Hz
Power Supply Consumption: ........................................................................................................... 200VA Maximum
Physical
Dimensions: ............................................................................................. 17"(43cm) W x 17"(43cm) D x 4"(10cm) H
Weight: ................................................................................................ 9.1Kg (20 lbs.) Net; 11.8Kg (26 lbs.) Shipping
4
Accuracy specifications valid following a 30-minute warm-up at an ambient temperature between 5°C and 50°C.

12
Getting Started
4-Wire Configuration
Figure 2 illustrates how the 4-wire principle is used to eliminate lead, wire, and contact resistances as
potential error sources. The internal current source inherently overcomes all series resistance (within
compliance voltage limits) and delivers a precise constant current. The internal high-impedance DVM
senses the voltage drop across the load. There is negligible contact and lead resistance error created by
the voltage measurement because the high input impedance of the DVM limits current flow in the voltage
leads.
This section covers the fundamentals of ohmmeter operation. This section will demonstrate 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 define the sections of the front
and rear panel of the 4300C.
Figure 2 – 4-Wire Configuration

13
Front Panel
The front panel of the 4300C can be broken down into nine parts.
Figure 3 - Front Panel Sections
On/Off 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.
Display
During measurements, the display presents 3 windows described in the image below. The display is also
used to prompt the user with alerts and messages.

14
Range Selection and Test Current Key
Range Selection
The 4300C has 3 voltage settings and 6 current ranges. The combination of the two result in 18 possible
resistance measurement ranges.
Voltage Setting
20mV
200mV
2V
Current Range
10A
1) 2mΩ
7) 20mΩ
13) 200mΩ
1A
2) 20mΩ
8) 200mΩ
14) 2Ω
.1A
3) 200mΩ
9) 2Ω
15) 20Ω
10mA
4) 2Ω
10) 20Ω
16) 200Ω
1mA
5) 20Ω
11) 200Ω
17) 2kΩ
.1mA
6) 200Ω
12) 2kΩ
18) 20kΩ
The two keys labeled F.S. Voltage are used to change the voltage setting. The ñ key
is used to increase the voltage setting and the ò key is used to decrease the setting.
Within a voltage setting there are six possible Ohms Ranges. The two keys labeled
Ω Range are used switch between the ranges. The ñ key is used to increase the
range and the ò key is used to decrease the range. As the Ohms range increases,
the current range decreases and vice versa.
Test Current Key
The Test Current key is used to turn the current source ON and OFF. A red LED
within the Test Current key indicates the status of the current source.
The current source may also be turned on and off via a command from one of the interfaces, or by a
remote foot switch Option "RS".
Function/Numerical Keys
There are sixteen Function/Numerical keys which are used to
trigger the standard and/or optional ohmmeter functions and
for data entry. Figure 4 depicts the key arrangement while
table 3 lists a brief description of the keys and their use. 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.
Figure 4

15
Function and Numerical Keys Description
Key
#
Description
Func.
-
The “FUNC.” key is used in combination with other keys to change stored settings. This key is also used
as a “Forward” key to skip through screens.
View
0
The “VIEW” key is used in combination with other function keys. It is used to view stored settings.
Update
1
The “UPDATE” key is used to set and/or view display update rate and intensity.
HLC
2
The “HLC” key is used to enable or disable the 4300C’s internal “Multi-Range Dual Limit
Comparator. Also used to set and/or view the limits used.
Addr.
3
The “ADDR.” key is used to view the setting information for all the standard or optional remote
interfaces.
Run/Hold
4
The “RUN/HOLD” key is used to switch between run and hold state. Also used to select the hold
configuration.
Print
5
The “PRINT” 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.
-
6
-
-
7
-
Cal
8
The “CAL” key is used to initiate the standard and TCM calibration procedure.
BCD
9
The “BCD” key enables the binary coded decimal output on models where the BCD option is
installed.
Clear
-
The “CLEAR” key functions like a backspace when entering values. The key is also used to return
to the previous screen.
Reset
-
The “RESET” key resets the ohmmeter returning it to Start-Up state.
Local
-
The “LOCAL” key is used to return from a remote to a local state.
Enter
-
The “ENTER” key is the user confirmation to a display prompt.
Store
-
The “Store” key is used to store the active range as default.
Table 3 - Function and Numerical Keys Description

16
TC Mode Key and Sensor Receptacle
This portion of the front panel is utilized only during
temperature compensated type measurements (TCM). TCM
mode is described in detail in the next section.
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
5
, 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.
The TCM feature of the 4300C, arithmetically calculates the resistance value to display utilizing the
ambient temperature and other parameters that will be present later. 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 located within the TCM key is the visual indication that the TCM mode is on. A “Fault”
message on the display indicates a missing sensor or that the sensor is not properly inserted in the
receptacle.
The TCM key is used to enable or disable the TCM mode.
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 the
next section. The HLC LEDs are active only when the Hi-Lo comparator
mode (HLC) is in use. The green LED, labeled “GO”, is on if the
measured resistance value is between the limits
6
set by the user. The
yellow LED, labeled “LO”, is on if the measured resistance value is less than the lower limit. The red LED,
labeled “HI”, is on if the measured resistance value is greater than the upper limit.
Cable Disconnect Status Indicators
The SAFE and UNSAFE LEDs indicate whether it is safe to disconnect
the test leads from the load or from the instrument. When a highly
inductive load is being measured, a potentially lethal back-EMF is
induced when the test current is removed. The 4300C provides a
discharge path for this back-EMF and monitors the voltage. The SAFE
LED is illuminated when the back-EMF is less than five volts.
5
The Omni Compensator is an optional accessory to the 4300C. See Measurement Modes and Functions for more
detail.
6
See Page 30 for detail on how to set the Hi-Lo limits.

17
Although the 4300C is protected against up to 500 Amps of inductive
kickback, it is not advisable to remove test leads with the Test Current
On, or with the UNSAFE LED lit. In some extreme applications if leads are
removed or pull loose before the SAFE LED is lit, damage may occur to
the 4300C and/or injury to the operator!
The UNSAFE LED is also illuminated whenever a test current of .1A or greater is selected and the Test
Current is on, regardless of the load.
Charging Inductor Mode
The Charging Inductor mode LED indicates when the standard current source
compliance voltage of 7V is exceeded. In this situation the 4300C provides a
booster shot more than 20V to reduce the settling time when a large inductive
load is being measured. The display readings should be ignored when this LED is
illuminated.
Source and Sense Binding Post
Connections to the 4300C are made via the front panel source/sense
terminals, which consist of two red and two black heavy duty 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
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.
When using Valhalla test leads, the tabbed side of each banana jack is connected to the current terminals.
This ensures that current is carried in the largest conductor of the cable, and that the voltage input is
shielded.
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 4300C
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 resistance of the current carrying
leads. The 4-wire principle is used to eliminate lead, wire,
and contact resistances as potential error sources.

18
Rear Panel
The rear panel of the 4300C may vary from unit to unit according to the optional features installed. This
section of the manual refers to the standard model without any optional features or modifications. If the
4300C that you are using features terminals or connectors not described in this section, please refer to
the addendum section that may reference the particularities of your model. Here is an outline to the use
of each of the rear panel controls and connectors.
Figure 5 - Rear Panel Sections
Line Voltage Switch
The line voltage switch allows the user to select the power settings according to the
local AC line voltage. By sliding the switch upwards, the number 115 will appear on
the switch. The instrument is now configured for line voltages of 115VAC ± 10%. By
sliding the switch downwards, the number 230 will appear. The instrument can now
be used with line voltages of 230VAC ±10%. Prior to powering on the ohmmeter, it is
important to verify that the switch is set for the correct line voltage.
Selecting the incorrect line voltage setting may cause damage to the
instrument!
Fuse Holder
The line power fuse must match the line voltage selection as follows:
• 105-125VAC – 3A SLO-BLO
• 210-250VAC – 1.5A SLO-BLO
The fuse holder is located on the rear panel. To install a fuse, first disconnect the Ohmmeter’s power cord.
Insert one end of the fuse into the fuse cap. Insert the fuse cap into the fuse holder. With a small flathead
screwdriver, push in on the fuse cap and rotate it clockwise.