Tegam R1L-B User manual

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R1L-B
MICROOHMMETER AND BOND
TESTER
MODEL R1L-B
Instruction Manual
PN# R1L-B-900-01
Publication Date: November 2013
REV. F
REPRODUCTION AND DISTRIBUTION OF THIS TECHNICAL MANUAL IS AUTHORIZED FOR US
GOVERNMENT PURPOSES. TEGAM PROPRIETARY INFORMATION.
NOTE: This User’s Manual was as current as possible when this product was manufactured. However,
products are constantly being updated and improved. To ensure you have the latest documentation, refer
to www.tegam.com

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TABLE OF CONTENTS
TABLE OF CONTENTS
1. INSTRUMENT DESCRIPTION
Purpose ...............................................................1-1
Performance Characteristics ...................................1-1
Description of Equipment .......................................1-2
Figure 1: Front Panel Controls.............................1-3
List of Items Furnished ..........................................1-4
Storage and Shipping Requirements ........................1-4
2. PREPARATION FOR USE AND INSTALLATION
Unpacking and Inspection ......................................2-1
Preparation for Use................................................2-1
3. OPERATING INSTRUCTIONS
Pushbutton Functions ............................................3-1
General Theory of Operation...................................3-2
4. PRINCIPLES OF OPERATION
Principles of Operation...........................................4-1
5. MAINTENANCE
Inspection............................................................5-1
Cleaning ..............................................................5-1
Test Equipment required for Calibration and Repair ...5-1
Calibration ...........................................................5-2
Troubleshooting ....................................................5-6
Table 2: Fault Symptoms and Repair Actions ........5-6
Preparation for Shipment .......................................5-7
Overhaul Instructions ............................................5-8
Figure 2: Parts Layout........................................5-8
Figure 3: Digital Section.....................................5-9
Figure 4: Digital Section...................................5-10
Table 3: Parts List – Main Board Assembly..........5-11
Table 4: Parts List – Front Panel Assembly..........5-14
Table 5: Vendor Cage Code Directory.................5-17
6. SERVICE INFORMATION
Preparation for Repair or Calibration Service.............6-1
Expedite Repair and Calibration Form ......................6-2
Warranty..............................................................6-3

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1-1
INSTRUMENT DESCRIPTION
SECTION 1
INSTRUMENT DESCRIPTION
INTRODUCTION
1.1 Purpose
The Model R1L-B is a digital Microohmmeter / Bond Tester
with full scale ranges from 2 mΩ to 20 Ω. The resistance
reading is displayed on a 3½ digit liquid crystal display on
the front panel. An over-range condition is indicated as a "1"
followed by three blank digits (the decimal point is also
displayed in its normal position for the range selected).
A rugged version, Model R1L-BR is also available, which is
electronically identical to model R1L-B, but it has a rugged
case as the enclosure rather than an open front panel.
1.2 Performance Characteristics
This is a range-selection instrument, with a rotary 5 range
selector switch.
Range
Full
Scale (Ω)
Resolution
(Ω)
Test Current
Peak (A)
1
1.999 m
1 µ
1.4
2
19.99 m
10 µ
140 m
3
199.9 m
100 µ
14 m
4
1.999
1 m
1.4 m
5
19.99
10 m
140 µ
Table 1: Specifications
Accuracy:
Accuracy on all ranges: ± (0.25% of reading + 1 count),
when powered from the batteries only.

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INSTRUMENT DESCRIPTION
1.3 Description of Equipment
Physical: The circuitry is enclosed in a rugged bench top
case.
Dimensions: 101 mm (4”) x 292 mm (11.5”) x 203 mm (8”).
Weight is 1.6 kg (3.6 lb). Controls and connectors are of a
size and spacing such that the instrument may be operated
while wearing safety gloves.
Electrical: The R1L-B is powered by an internal battery
consisting of three rechargeable NiCad ‘C’ cells (3000 mAh)
with a built-in charger. Input power for the charger is 90 to
250 VAC at 50 Hz or 60 Hz. Charging power is supplied via a
removable line cord; one end of which plugs into a line filter on
the front of the R1L-B, and the other end being a standard
three-pin grounded line plug.
Input Protection: The R1L-B will not be damaged by a signal
of 1 Vp-p applied across any pair of input terminals.
Environmental: This unit will operate over a temperature
range from 0 °C to 50 °C, 75% RH non-condensing, up to
3050 m altitude.
Front Panel Controls and Displays (See figure 1)
RANGE Switch. The rotary 5 range selector switch may be
used to step through all five ranges.
POWER Switch. Used to turn the power on or off to the
instrument.
DISPLAY is a 3 ½ digit, displaying readings from 1.999 to
199.9.
Four binding posts for connection of test leads are marked
+I, +E, -E, and -I. Proper connections to the resistor under
test are described in Section 3.2 below.

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1-3
INSTRUMENT DESCRIPTION
WARNING
DO NOT TOUCH THE BINDING POSTS WHEN THEY ARE
CONNECTED TO EXTERNAL CIRCUITS. LETHAL
VOLTAGES MAY BE PRESENT AT THESE POSTS.
Figure 1: Front Panel Controls

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1-4
INSTRUMENT DESCRIPTION
1.4 List of Items Furnished
1 each Model R1L-B with power cord
3 each rechargeable battery cells (P/N: BA-110)
2 each Kelvin Clip Cables, one end with a dual banana
plug and the other end with a gold plated Kelvin clip
(P/N: KTL-100)
1 each R1L-B Instruction Manual (P/N: R1L-B-900-01)
1.5 Storage and Shipping Requirements
Standard precautions which apply to electronic test
instruments should be followed. A hard mechanical
shock, such as from dropping the R1L-B, could damage
the liquid crystal display. Care should be taken to
prevent damage to associated cables.
The R1L-B should be stored in a relatively dust-free
environment. Remove the battery cells for inactive
storage of 30 days or more.
Temperature: -40 °C to +71 °C.
Relative humidity: 0 to 100%, non-condensing.
Altitude: 4570 m
See Section 5.7 below for shipping requirements.

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2-1
PREPARATION FOR USE AND INSTALLATION
SECTION 2
PREPARATION FOR USE AND INSTALLATION
2.1 Unpacking and Inspection
Upon receipt, the R1L-B and accessories should be carefully
unpacked and removed from the shipping container.
Separate the units from the packing material and inspect
both the instrument and the accessories for any external
damage.
•If any dents, broken, or loose parts are seen, do not use
the equipment. Notify TEGAM immediately.
•Check that all items are present. If any items are missing,
notify TEGAM immediately.
2.2 Preparation for Use
Battery Installation
Note that the instrument is shipped with its battery
removed. Unwrap the 3 cells which comprise the battery.
Be sure the power line cord is disconnected. Check that the
Power Switch is in the OFF position. Remove the four screws
at the corners of the R1L-B’s top (control/display) panel.
Carefully lift the unit out of its cabinet. Place the unit upside
down on a surface which will not mar or damage the
control/display panel.
WARNING
DO NOT CONNECT THE AC LINE CORD PRIOR TO
REMOVING THE UNIT FROM ITS CASE OR WHILE THE
UNIT IS OUT OF ITS CASE, OR ELSE THE MAINS VOLTAGE
WILL PRESENT A POSSIBLE SHOCK HAZARD.

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2-2
PREPARATION FOR USE AND INSTALLATION
CAUTION
BE SURE TO OBSERVE THE PROPER POLARITY WHEN
INSERTING THE BATTERY CELLS OR DAMAGE MAY
RESULT.
Insert the battery cells, one at a time, in accordance with
the polarity indications marked on both the battery cell and
the battery holder. Insert the positive end of the battery
cells first.
After installing the cells, reinstall the instrument in its case
and secure the four corner screws.
Power Up
Plug the power cord into the R1L-B front panel receptacle,
and plug the other end into a standard AC outlet. For battery
operation (with charged battery cells), this step is omitted.
Turn on the POWER rotary switch. Note that this switch
turns on both line and battery power.
Charging the Battery Cells
Prior to battery operation, it is recommended the R1L-B
Microohmmeter be plugged into AC power for at least 14
hours to charge the battery cells. To charge the battery
cells, the Power Switch must be turned ON, and the Range
Switch should be set to 20 Ω. With the Range Switch set to
lower ranges, the charge rate decreases and the batteries
will be discharged, especially on the 2 mΩ range, even with
no resistance connected to the instrument. (However, the
discharge rate in this range will permit operation for at least
14 hours with no resistance connected.)
WARNING
ALTHOUGH THE FRONT PANEL IS NORMALLY GROUNDED
VIA THE GROUND PIN OF THE POWER CABLE, IF THIS
CONNECTION IS FAULTY AND IF THE HIGH SIDE OF THE
POWER CABLE IS SHORTED TO THE PANEL, THE PANEL
COULD POSSIBLY HAVE MAINS VOLTAGE ON IT
; SO DO
NOT TOUCH THE PANEL WHEN AC POWER IS
CONNECTED.

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3-1
OPERATING INSTRUCTIONS
SECTION 3
OPERATING INSTRUCTIONS
The R1L-B is designed for bench-top operation. Use the
cables connecting their banana plug terminations to the four
binding posts marked +I, +E, -E, and -I.
3.1 Rotary Switch Functions
Operation of the Model R1L-B is extremely simple. There are
only two switches.
The RANGE rotary switch manually scrolls through the five
ranges.
Full scale on any range may be described as 2,000 (actually
1,999), since this is a 3½ digit meter. If the readings are
exceeding 1,999 counts, step to the next higher range. If the
readings are less than 2,000 counts, step down a range, so
that it will read 1,999 counts, or less. The decimal point is
located automatically for the correct reading.
If the selected range is too low for the value of the resistor
under test, the display will show over-range.
The POWER rotary switch turns on the power to operate the
unit or turns off the power to the unit. The appearance of the
display will show that power is on; absence of the display
indicates that either power is off, batteries are discharged, or
there is some malfunction. Note that when power is turned
off, it may take several seconds to discharge circuit capacity
to completely blank the display. The black markings seen
have no effect and disappear when power is turned back on.

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3-2
OPERATING INSTRUCTIONS
3.2 General Theory Of Operation
Measurement Principle
A 4-terminal measurement method is used to determine the
resistance of the item under test. This method allows the
accurate measurement of low values of resistance in spite of
the other resistances present in the connection leads. A
known current is supplied to the item under test via two wire
leads connected to the +I and -I binding posts on the R1L-B
Microohmmeter front panel. Two other wire leads connected
to the +E and -E binding posts on the R1L-B front panel
sense the voltage developed across the resistance under test
due to the supplied known current. The R1L-B then calculates
the resistance of the item under test utilizing Ohm's law, and
displays it on a 3 ½ digit display.
Kelvin Klip Cable Description
A Kelvin clip consists of two opposing jaws of an alligator
style clip which are insulated from each other, so one jaw may
be used to connect a source of current to the resistance
under test, and the other jaw used to measure the voltage at
the test point. The two jaws are spring loaded to clamp onto
a cylinder of ½ inch diameter or less.
WARNING
OPERATING THE R1L-B MICRO
OHMMETER AND TAKING
RESISTANCE
MEASUREMENTS ON A POWERED OR
ENERGIZED COMPONENT COULD CAUSE SERIOUS HARM
TO THE OPERATOR AND/OR DAMAGE THE R1L-
B. BE
SURE THE ITEM TO BE MEASURED IS DISCONNECTED
FROM OTHER COMPONENTS AND APPARATUS.
If the battery cells have not been installed, refer to section
2.2.Battery only operation will result in the most stable and
accurate readings. The R1L-B may be operated while
charging the batteries, however it will not conform to
specifications in this configuration.

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3-3
OPERATING INSTRUCTIONS
NOTE: The amount of current available for charging the
battery decreases as lower resistance ranges are selected. In
the 2 mΩrange, the current supplied to the resistance under
test exceeds the charging current, and the battery will be
drained.
To obtain the best accuracy, allow the R1L-B to warm up for
15 minutes on the 20 Ωrange before making measurements.
Even if in battery operation, this will not cause appreciable
battery discharge.
Using the Kelvin-Clip cables
Plug one Kelvin-Clip cable dual banana plug across the +E
and +I binding posts, and plug the other Kelvin-Clip cable
dual banana plug across the -E and -I binding posts. Note
that in both cases, the small "I" marked on the dual banana
plug should go into the respective I binding post.
If Kelvin-Clip cables are not used, a pair of shielded cables
may be utilized. As occurs in the Kelvin-Clip cables in the
above paragraph, one cable should have its shield connected
to the “+I” binding post and its center conductor connected
to the +E binding post. Similarly, the other cable should
have its shield connected to the -I binding post and its
center conductor to the -E binding post. It is also
recommended that the resistance of the cables should not
exceed 1 Ω.
NOTE: Particularly in the 2 mΩrange, where a test current
of approximately 1.5 A is used, excessive lead resistance
will prevent an accurate measurement.
Set the Range Switch to the desired measurement range and
read the resistance on the liquid crystal display. If the
resistance is higher than the selected range, the display will
show a "1" and three blank digits, indicating over-range. The
decimal point will also appear in the proper location for the
selected range.

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3-4
OPERATING INSTRUCTIONS
After prolonged operation on battery power, when the
battery voltage approaches the end of its useful range, the
"LO BAT" indicator will be seen on the display. Although the
battery cells are not fully discharged and they will not be
damaged by additional use, this is a warning to the operator
that the battery cells need to be charged.
Use of HTP-100 probes with R1L-B
1. Connect the BLUE spade lug from the LEFT HTP-100
Probe to the RED E+ terminal of the R1L-B.
2. Connect the RED spade lug from the LEFT HTP-100 Probe
to the RED I+ terminal of the R1L-B.
3. Connect the WHITE spade lug from the RIGHT HTP-100
Probe to the BLACK E- terminal of the R1L-B.
4. Connect the BLACK spade lug from the RIGHT HTP-100
Probe to the Black I- terminal of the R1L-B.
5. Hold the RED HTP-100 Probe in your left hand and the
WHITE HTP-100 Probe in your right hand, and push the
probe points against the surface to be measured with
sufficient force to cause the points to retract slightly.

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4-1
PRINCIPLES OF OPERATION
SECTION 4
PRINCIPLES OF OPERATION
Power Supply
The internal switching power supply U8 accepts nominal line
voltages between 90 and 250 VAC 50/60 Hz, allowing
operation worldwide. C1, C2, U1, R1, R2 and R101 form a
constant current regulator set to approximately 758 mA for
charging the battery. D5 is used to isolate the AC power for
the battery. D7 serves to clamp the voltage to less than 5 V
when the battery is disconnected. The negative 3.6 volt
power supply for U2 and U10 is developed by U5.
Test Current Path
The test current used to perform the resistance
measurement originates from the battery + terminal
connected to the +3.6 V power symbol at the emitter of Q1.
It flows through Q1 into the COM1 terminal of SW1 and out
of the terminal selected by the switch for the measurement
range chosen. Each pole of the COM1 section of SW1 is
connected to a different tap on the current sensing resistor
string made up of R13, R48, R50, R52 and R54. The test
current flows into the sense resistor string at the tap
selected, out of R54 into D3 and out of D3 to the I+ test
jack. The external test leads conduct the current through the
resistance being measured and back to the I- test jack,
where it returns to ground and then to the battery -
terminal.
Test Current Regulator
The test current is controlled to a constant value for each
range with a feedback loop. The main loop amplifier is U9A.
The output of U9A controls the conduction of Q1 using Q2,
such that if the output voltage of U9A increases, the test
current increases. The inputs of U9A compare the voltage
across the current sensing resistor string with a 3 volt
reference voltage produced by U4, the voltmeter IC. The
voltage across the sensing resistor string is maintained at
1.5 V, half the value of the reference voltage because R9 and

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4-2
PRINCIPLES OF OPERATION
R11 are twice the value of R8 and R9. The reference voltage
of 3 V is present between the VREF signal at one end of R9
and the +3.6 V power supply present at one end of R11. The
voltage at one end of the sensing resistor string is present at
U11A pin 1 which feeds R8. The voltage at the other end of
the sensing resistor string is present at U11B pin 7 which
feeds R10. U11A and U11B are very high input impedance
buffer amplifiers which sense the voltage across the current
carrying portion of the sensing resistor string without
causing errors in the test current. R127, R129 and CR1
provide overvoltage input protection for pin 3 of U11A, and
similarly R46, R128 and CR2 for U11B. U2B will shut off the
current source if the voltage on the I+ binding post becomes
less than about -3 V.
Test Current Adjustment
The test current on the 2 milliohm range is 1.4 amps. It is
very stable, but not adjustable. The 1.4 A current stability is
determined by the stability of R54, the 3 V reference
developed by U4 and to a minor extent other circuit
components. The test currents on the four other ranges are
adjusted to approximately 1/10, 1/100, 1/1000 and 1/10000
of the actual value of the 2 milliohm range test current
during the calibration/ adjustment process. Trimpots R53,
R51, R49 and R114 are used for this adjustment, and are
adjusted sequentially in that order. Adjusting the current
affects the readings, so current adjustment INDEPENDENT of
the readings adjustment is not possible.
Voltage Measurement
The voltage across the resistance being measured is
amplified by U10A, U10B and U9B. The E+ and E- test jacks
are the input to this differential amplifier, and the output is
connected to the voltmeter IC U4 pins 38 and 39. R130,
R131, R141, R142, CR3 and CR4 provide overvoltage input
protection. U10A, U10B, R132, R133 and R134 provide a
differential gain of 5: the voltage between U10A pin 1 and
U10B pin 7 is 5 times the voltage between E- and E+. U9B
provides voltage gain of 10, and develops its output between
VREF at pin 40 of U4 and VIN+ at pin 39 of U4. An

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4-3
PRINCIPLES OF OPERATION
adjustable bipolar offset voltage is added to this output by
R143 before it is applied to VIN- at pin 38 of U4. C18 and
140 are a low pass filter to reduce noise.
The voltmeter IC U4 converts the amplified voltage across
the resistance being measured into a displayed reading.
Because the test current is precisely regulated along with the
various gains chosen in the circuit, the displayed value is
directly proportional to the resistance being measured. U4
develops a reference voltage of 3 V between pins 8 and 40.
The reference is divided by the resistor string R31, R32,
R146 and R143. R146 provides an adjustable voltage used
as the analog to digital conversion reference to pin 44. R143
provides an adjustable zero reading.
Display
U4 directly drives the LCD, except for the decimal points and
the LOBAT indicator. The decimal point associated with the
range selected is displayed when the range switch SW1
provides a +3.6 V signal to one of the inputs of U7. The
LOBAT signal is displayed when U2A detects the voltage at
pin 40 of U4 falls below ground. Since this pin is maintained
by U4 at the reference voltage of 3 V below the battery
voltage, LOBAT will be displayed when the battery is less
than approximately 3 V.

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5-1
MAINTENANCE
SECTION 5
MAINTENANCE
5.1 Inspection
These units should be inspected semi-annually. Cables
should be periodically inspected to make sure they are in
good condition. Check that the switches turn smoothly.
Check all four binding posts to ensure that they operate
smoothly.
No other maintenance is required, other than to keep the
battery charged through power line operation. Charging
should be done for at least 14 hours after long periods
(several months) of storage or after considerable use on
battery power.
5.2 Cleaning
The instrument should be cleaned periodically, as is
necessary, using mild soap and a damp cloth both followed
by second damp rinsing cloth.
Clean the LCD window using a soft cloth moistened with
water or "Windex" type window cleaner. DO NOT use
common paper towel products as some brands may contain
fibers which could scratch the display window. DO NOT apply
significant pressure to the LCD as it could separate from the
front panel. DO NOT use alcohol, solvents, or harsh
chemicals to clean the LCD window.
5.3 Test Equipment and Tools Required for Calibration
and Repair
Calibration of the R1L-B is recommended on a yearly basis,
and is done at a temperature of 23 °C ± 1 °C. To obtain
best results, keep the unit at 23 °C ± 1 °C for at least 8
hours, and allow it to warm up for 30 minutes before
making any adjustments.

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5-2
MAINTENANCE
(The calibration procedure and schematics provided in this manual are for
the surface mount units manufactured after November 2013. Please
contact TEGAM if your instrument is purchased prior to that date.)
Precision four terminal resistors with accuracy of 0.05% or
better: 1 mΩ, 1.9 mΩ, 19 mΩ, 190 mΩ, 1.9 Ω, and 19 Ω
A standard 4 ½ digit digital voltmeter: with 2 V range,
accuracy better than 0.03% of reading ±1 count.
Screwdrivers: Medium Phillips and small slotted for trim-pot
adjustment.
Three 20 AWG approximately 4 inch long Bus Wires
Four 18 AWG Wires (or dual wire cable) approximately 2 feet
long with clips
5.4 Calibration
CAUTION
SAFETY PRECAUTIONS MUST BE TAKEN WHEN HANDLING
THIS
INSTRUMENT WHEN THE LINE CORD IS PLUGGED IN
AND THE R1L-
B HAS BEEN REMOVED FROM ITS CASE, TO
ENSURE THAT CONTACT IS NOT MADE WITH THE AC
POWER CONNECTIONS OR OTHER POTENTIALLY HARMFUL
POINTS. FAILURE TO OBSERVE PROPER SAFETY
PRECAUTIONS MAY CAUSE SERIOUS H
ARM TO THE
OPERATOR AND/OR DAMAGE THE R1L-B.
A. Preparation
1. Remove the front panel assembly from the case by
removing the four retaining screws. Retain the four
screws for reinstallation.
2. Install a new set of approved batteries into the UUT
as required. Observe polarity.
3. Plug UUT in and turn on setting the range switch to
20 Ωrange, allow a 14 hour charge time. (Skip this
step if batteries have already been charged.)
4. After the UUT has been charged, unplug the UUT.
5. Allow a 10 minute COOL DOWN.

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MAINTENANCE
NOTE: Heat from the charging circuit causes the UUT to
drift. The COOL DOWN period is only necessary if the UUT
has been charging for an extended period of time.
6. Turn the voltmeter on allowing a 10 minute warm up.
a) Set unit to measure DC voltage.
b) Set unit to Auto range.
7. Connect clip leads to the voltmeter.
B. AC Circuitry Check
1. Set the range switch to 20 Ω on the UUT.
2. Connect the voltmeter to the UUT;
a) Voltmeter Red test lead to TP1 of the UUT,
b) Voltmeter Black test lead to TP2 of the UUT.
3. Plug the UUT into AC and turn on.
4. Verify the reading on the voltmeter reads between
1.0 to 1.5 VDC.
5. Disconnect the UUT from the AC source.
6. Disconnect the Voltmeter from the UUT.
NOTE: The UUT is to be unplugged from AC during the
remaining portions of the procedure.
C. Zero the Display
1. Set the range switch to 2 mΩ on the UUT.
2. Short out all four terminals of the UUT in the following
order, +I to –I, –I to +E, +E to –E using the three
pieces of buss wire.
3. Adjust R143 for a zero reading ±1 count on the least
significant digit as displayed by the UUT.
4. Set the range switch to the next higher range.
5. Verify a zero reading within ±1 count on the least
significant digit.
6. Repeat steps 4 and 5 for all remaining ranges.
7. Disconnect the buss wires from the UUT.
D. 2 mΩ Adjust (Main Gain Adjust)
1. Set the range switch to 2 mΩon the UUT.
2. Connect a 1.9 mΩstandard to the UUT using the clip
leads.

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5-4
MAINTENANCE
3. Adjust R32 for a display reading of the actual
standards value ±3 counts (±0.003 mΩ) on the
display of the UUT, typically 1.900. Allow adequate
time for any thermals to dissipate and the unit to
settle.
4. Repeat sections C-D until both values are with-in
specifications.
5. Disconnect the resistance standard.
6. Connect a 1 mΩstandard to the UUT using the clip
leads.
7. Verify that the display of the UUT displays the actual
standard value ±2 counts.
8. Disconnect the resistance standard.
NOTE: The following adjustment steps build upon each
other, and must be performed in sequence. It appears that
the connection of standards will be more convenient if the
steps are performed in reverse order, from H to E, but this
will not provide a satisfactory adjustment, as (for example)
the Step E adjustment changes the Step H reading.
E. 20 mΩAdjust
1. Set the range switch to 20 mΩon the UUT.
2. Connect a 19 mΩstandard to the UUT using the clip
leads.
3. Adjust R53 for a display reading of the actual
standards value ±3 counts (±0.03 mΩ) on the display
of the UUT, typically 19.00. Allow adequate time for
any thermals to dissipate and the unit to quit drifting.
4. Disconnect the resistance standard.
5. Connect a 1.9 mΩstandard to the UUT using the clip
leads.
6. Verify that the display of the UUT displays the actual
standard value ±2 counts.
7. Disconnect the resistance standard.
F. 200 mΩAdjust
1. Set the range switch to 200 mΩon the UUT.
2. Connect a 190 mΩstandard to the UUT using the clip
leads.

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5-5
MAINTENANCE
3. Adjust R51 for a display reading of the actual
standards value ±3 counts (±0.3 mΩ) on the display
of the UUT, typically 190.0. Allow adequate time for
any thermals to dissipate and the unit to quit drifting.
4. Disconnect the resistance standard.
5. Connect a 19 mΩstandard to the UUT using the clip
leads.
6. Verify that the display of the UUT displays the actual
standard value ±2 counts.
7. Disconnect the resistance standard.
G. 2 ΩAdjust
1. Set the range switch to 2 Ωon the UUT.
2. Connect a 1.9 Ωstandard to the UUT using the clip
leads.
3. Adjust R49 for a display reading of the actual
standards value ±3 counts (±0.003 Ω) on the display
of the UUT, typically 1.900. Allow adequate time for
any thermals to dissipate and the unit to quit drifting.
4. Disconnect the resistance standard.
5. Connect a 190 mΩstandard to the UUT using the clip
leads.
6. Verify that the display of the UUT displays the actual
standard value ±2 counts.
7. Disconnect the resistance standard.
H. 20 ΩAdjust
1. Set the range switch to 20 Ωon the UUT.
2. Connect a 19 Ωstandard to the UUT using the clip
leads.
3. Adjust R114 for a display reading of the actual
standards value ±3 counts (±0.03 Ω) on the display
of the UUT, typically 19.00. Allow adequate time for
any thermals to dissipate and the unit to quit drifting.
4. Disconnect the resistance standard.
5. Connect a 1.9 Ωstandard to the UUT using the clip
leads.
6. Verify that the display of the UUT displays the actual
standard value ±2 counts.
7. Disconnect the resistance standard.