Simpson 260 8P User Manual

Simpson 260® Series 8P
Volt-Ohm-Milliammeters
INSTRUCTION MANUAL

About this Manual

To the best of our knowledge and at the time written, the information contained in
this document is technically correct and the procedures accurate and adequate to
operate this instrument in compliance with its original advertised specifications.

Notes and Safety Information

This Operator’s Manual contains warning headings which alert the user to check
for hazardous conditions. These appear throughout this manual where applicable,
and are defined below. To ensure the safety of operating performance of this in­strument, these instructions must be adhered to.

Warning, refer to accompanying documents.

!

Caution, risk of electric shock.

!

This instrument is designed to prevent accidental shock to the operator when
properly used. However, no engineering design can render safe an instrument
whick is used carelessly. Therefore, this manual must be read carefully and com­pletely before making any measurements. Failure to follow directions can result
in serious or fatal accident.

Shock Hazard: As defined in American National Standard, C39.5, Safety Re­quirements for Electrical and Electronic Measuring and Controlling Instrumenta­tion, a shock hazard shall be considered to exist at any part involving a potential
in excess of 30 volts RMS (sine wave) or 42.4 volts DC or peak and where a
leakage current from that part to ground exceeds 0.5 milliampere, when mea­sured with an appropriate measuring instrument defined in Section 11.6.1 of
ANSI C 39.5.

Technical Assistance

SIMPSON ELECTRIC COMPANY offers assistance Monday through Friday
7:30 am to 5:00 pm Central Time by contacting Technical Support or
Customer Service at [phone].
Internet: http://www.simpsonelectric.com

Warranty and Returns

SIMPSON ELECTRIC COMPANY warrants each instrument and other articles
manufactured by it to be free from defects in material and workmanship under
normal use and service, its obligation under this warranty being limited to making
good at its factory or other article of equipment which shall within one (1) year
after delivery of such instrument or other article of equipment to the original pur­chaser be returned intact to it, or to one of its authorized service centers, with
transportation charges prepaid, and which its examination shall disclose to its
satisfaction to have been thus def ectiv e; this warranty being expressly in lieu of all
other warranties expressed or implied and of all other obligations or liabilities on
its part, and SIMPSON ELECTRIC COMPANY neither assumes nor authorizes
any other persons to assume for it any other liability in connection with the sales
of its products.

This warranty shall not apply to any instrument or other article of equipment which
shall have been repaired or altered outside the SIMPSON ELECTRIC COMPANY
factory or authorized service centers, nor which has been subject to misuse, neg­ligence or accident, incorrect wiring by others, or installation or use not in accord
with instructions furnished by the manufacturer.

2

NOTES:

3

Contents

1. INTRODUCTION ............................................................................... 6

1.1 General Description ........................................................................... 6

1.2 Overload Protection ............................................................................ 6

1.3 Internal Batteries ................................................................................ 7

1.4 Overload Circuit Test ..........................................................................7

1.5 Printed Circuit ..................................................................................... 8

1.6 Phenolic Case .................................................................................... 8

1.7 Adjust-A-Vue Handle .......................................................................... 8

1.8 Test Leads ..........................................................................................8

1.9 Technical Data .................................................................................... 8

1.10 Definition of Accuracy....................................................................... 1 0

1.11 Safety Considerations ...................................................................... 10

1.12 Audio Alarm ...................................................................................... 10

1.13 Accessory AC High Voltage Probe ................................................... 1 1

1.14 Amp-Clamp Model 150-2 ................................................................. 11

2. INSTALLATION ................................................................................ 11

2.1 Unpacking and Inspection ............................................................... 11

2.2 Warranty ...........................................................................................11

2.3 Shipping ...........................................................................................12

2.4 Power Source Requirements ........................................................... 12

2.5 Operating Position ............................................................................ 1 2

3. CONTR OLS, JA CKS, AND INDICATORS........................................ 12

3.1 Front Panel Description .................................................................... 1 2

4. OPERATION.................................................................................... 14

4.1 Safety Precautions ........................................................................... 1 4

4.2 Polarity Reversing ............................................................................ 15

4.3 Measurement of Unknown Voltage or Current ................................. 1 5

4.4 Test Leads ........................................................................................1 6

4.5 DC Voltage Measurement ................................................................ 1 6

4.5.1 DC Voltage Measurement 0-250 mV Range .................................... 16

4.5.2 DC Voltage Measurement 0-1V Range .............................................. 16

4.5.3 DC Voltage Measurement 0-2.5 Through 0-250V Range ................. 17

4.5.4 DC Voltage Measurement 0-500V Range ......................................... 17

4.5.5 DC Voltage Measurement 0-1000V Range ....................................... 18

4.6 AC Voltage Measurement .................................................................1 8

4.6.1 AC Voltage Measurement 0-2.5 Thru 0-250V Range ........................ 1 9

4.6.2 AC Voltage Measurement 0-500V Range .......................................... 20

4.6.3 AC Voltage Measurement 0-1000V Range ........................................ 20

4.7 Output Voltage Measurement ...........................................................21

4.8 Decibel Measurement (-20 To +50 dB) ............................................ 2 2

4.9 Direct Current Measurement ............................................................2 3

4.9.1 Direct Current Measurement 0-50µA Range .................................... 23

4.9.2 Direct Current Measurement 0-1mA Through 0-500mA Range ...... 23

4.9.3 Direct Current Measurement 0-10A Range ...................................... 24

4.10 Resistance Measurements ............................................................... 25

4.11 Measuring Resistance ..................................................................... 25

4.12 Resistance Measurement of Semiconductors ................................. 2 5

4.13 Continuity Tests.................................................................................26

5. OPERA T OR MAINTENANCE .......................................................... 27

5.1 Inspection .........................................................................................27

4

5.2 Battery Replacement ........................................................................ 2 7

5.3 Fuse Replacement ........................................................................... 27

5.4 Test Lead Inspection ........................................................................ 28

5.5 Care..................................................................................................28

5

1. INTRODUCTION

1.1 General Description

The Simpson Volt-Ohm-Milliammeter 260 Series 8P, (hereafter referred to as the
260 or as the Instrument) is a rugged, accurate, compact, easy-to-use Instrument
equipped with mirrored dial to eliminate parallax. The Instr ument can be used to
make accurate measurements of AC and DC voltage, direct current, resistance,
decibels, and Output Voltage. The Output Voltage function is used for measuring
the AC component of a mixture of AC and DC voltage. This occurs primarily in
amplifier circuits.
New Features in the 260-8P are:

0 - 25V AC/DC Range
Continuity Test Alarm
Individual Dual Jacks for the 500V AC/DC and 1000V AC/DC Ranges

1.2 Overload Protection

All the ranges, with exception of 1V, 10A, 50 µA, 250mV, 500/1000V AC and DC
are protected by an electronic overload protection system. The protection is from
the usual overloads that would damage the VOM. A transistor ized circuit senses
the voltage drop across the indicating instrument and actuates a relay when the
voltage reaches approximately three to four times rated full scale voltage. Sens­ing of the voltage drop is by means of a bridge network so that overload protec­tion is provided regardless of polarity. The relay operates at a uniform percent of
overload since the indicating instrument circuit is common to all ranges. When
actuated by an overload, the relay contacts, which are in the -COMMON CIR­CUIT, latch open until the reset button on the front panel is depressed. The reset
button is located to the right of the output jack.

!

Due to its sensitivity to overloads, the electronic overload protection relay incor­porated in the 260-8P is susceptible to electrostatic fields from high potentials or
transients either in the circuit being measured or in nearby circuitry.

Do not assume the relay to be faulty if it trips out without apparent cause. It may be
indicating a dangerous condition such as excessive circuit-to-ground (floating)
voltage being applied to the Instrument.

Avoid loading the Instrument or its test leads until certain that excessive circuit-to­ground voltage does not exist.

a. A switch that is opened when the relay latches, opens the relay circuit and

prevents continuous battery drain. This condition occurs when the reset but­ton has been pressed so that the VOM is operational; the protection circuit
draws less than the shelf life drain of the battery.

b. Since the 9V battery is used for both the R X 10,000V range and the protec-

tion circuit, the VOM is designed to allow the protection circuit to function
normally as long as the R X 10,000V range can be set to zero and an Alka­line Battery is used.

c. The 1 and 2 Amp fuses in the input circuit adds protection to the relay con-

6

tacts. Some overload conditions may cause the fuses to burn out as well as
open the relay contacts.

d. When an overload of sufficient magnitude is applied to the VOM, the reset

button will “pop-up” approximately 3/16" above the surface of the panel. To
reset the VOM for normal operation, first remove the overload and depress
the button. If the overload remains connected to the Instrument, resetting the
overload protection reset button will not connect the VOM input circuit.

In addition to the overload protection circuit, two diodes protect the indicating
instrument circuit. These diodes limit the current through the coil in case of over­load.

Fuses: Basic Overload protection is provided by a small inexpensive and easily
obtainable 3 AG type, 1 Amp , quic k-b low fuse. This fuse is rated to interrupt circuit
voltages up to 250 volts. A supplemental high energy fuse is provided for addi­tional protection from severe over loads. This fuse is the Bussman Type BBS 2A
600V. A Littlefuse Type BLS 2A 600V fuse may be used as a substitute replace­ment.

NOTES: If the 260-8P fails to indicate a reading, the 1 Amp or 2 Amp fuse may be
burned out. (Refer to paragraph 5.4 for fuse replacement.) Use only the specified
fuse type.

The 0-10A range is not fused. The shunt connects directly to the -10A and +10A
jacks.

The relay, fuse and diodes will prevent serious damage to the Instrument in most
cases of accidental overload. However, no overload protection system is com­pletely foolproof and misapplication on high voltage circuits can damage the
Instrument. Exercise care and caution to protect both the user and the Instrument.

1.3 Internal Batteries

There are two batteries in the ohmmeter circuits, a NEDA 13F size D cell that
furnishes 1.5-volts for the R X 1 and R X 100 ranges and a NEDA 1604A alkaline
battery that furnishes 9-volts for the R X 10,000 range and overload circuit. The

1.5-volt D cell is held in place with two spring clips which also serve as battery
contacts. The polarity symbols for the D cell are mark ed near the battery contacts.
The 9-volt battery is held in place with a spring clip, but contact is made with a
separate connector that is polarized. Always observe correct polarity when re­placing the 1.5-volt D cell.

!

The 9-volt battery must be installed and tested before the Instrument is ready for
use. Perform the overload test described in Paragraph 1.4 to ensure proper over­load circuit operation prior to using the Instrument.

1.4 Overload Circuit Test

a. Set the range switch to R X 10,000 POSITION and the function switch to -DC

POSITION.

b. Plug the black test lead into the -COMMON jack terminal and touch the other

end of the test lead to the +1 volt input terminal. (The relay reset button
should rise, indicating that the overload circuit is in working condition.)

NOTE: No damage will occur to the 260-8P as a result of this test.

7

1.5 Printed Circuit

Most of the component parts are mounted on a printed circuit board which simpli­fies assembly and maintenance, thus, extending the useful life of the Instrument.

1.6 Phenolic Case

The phenolic case is designed with heavy reinforced walls for maximum durabil­ity and provides excellent protection for the circuit components. The case has an
externally accessible battery and fuse compartment. Access to the batteries and
fuses is obtained by unscrewing a single captivated screw at the bottom of the
case and sliding out the compartment cover.

Rubber plug bumpers on the bottom of the case reduce sliding should the 260 be
accidentally pulled by the test leads when the Instrument is on a workbench.

1.7 Adjust-A-Vue Handle

A carrying handle is attached to the Instrument case. The handle may be used to
support the Instrument in a convenient sloping position for easy viewing. The
case can also be placed in either a vertical or horizontal position. The horizontal
position is preferable for greater accuracy since the Instrument is calibrated in
this position.

1.8 Test Leads

Each Instrument is furnished with one pair (Catalog Number 00043) of probe
type test leads (one red and one black, each 48 inches long) for all applications
of the Instrument. These test leads have elbow prods on one end, to connect the
leads to the recessed jacks on the Instrument front panel. The probe tips at the
opposite end have threaded shoulders to accept the screw-on insulated alligator
clips (furnished with the test leads) or the 5000 volt test probe(s) to extend the
Instrument AC or DC voltage range. The test leads and the insulated alligator
clips are rated for the voltage and current ranges available on the 260. Maximum
ratings are 1000V AC or DC or 10 DC amperes. These ratings for the test leads
must not be exceeded in any application.

1.9 Technical Data

1. DC VOLTS:
Ranges: 0-1-2.5-10-25-50-250-500-1000V
Sensitivity: 20,000 ohms per volt

2. DC MILLIVOLTS:
Range: 0-250mV
Sensitivity: 20,000 ohms per volt

3. AC VOLTS:
Ranges: 0-2.5-10-25-50-250-500-1000V
Sensitivity: 5,000 ohms per volt

4. OUTPUT VOL TAGE (AC):
Ranges: 0-2.5-10-25-50-250

Table 1-1. Technical Data

(limited to 350VDC)

8

5. DC MICROAMPERES:
Range: 0-50µA
Voltage Drop: 250mV

6. DC MILLIAMPERES:
Ranges: 0-1-10-100-500 mA
V oltage Drop (Approx.): 250 mV, 255 mV, 300 mV, 500 mV

7. DC AMPERES:
Range: 0-10A
Voltage Drop (Approx.): 255mV

NOTE: The 10A range is not internally fused.

8.

egnaR000,2-0 ⍀ 000,002-0 ⍀ M02-0 ⍀

:ECNATSISER1XR001XR000,01XR

gnidaeRretneC21 ⍀ 0021 ⍀ 000,021 ⍀

nepOlanimoN
egatloVtiucriC

trohSlanimoN

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V5.1V5.1V9

Am521Am52.1Aµ57

9. *ACCURACY:
DC Voltage Ranges: 2% of Full Scale
DC Current:

0-50 µA Range: 1.5% of Full Scale
Other Ranges: 2% of Full Scale
**AC Voltage

Ranges: 3% of Full Scale
Frequency Response: Referenced to 100 Hz (Figures 4-5 and 4-9)
Resistance Ranges:

R X 1: 2.5° of Arc

R X 100: 2°of Arc

R X 10,000: 2° of Arc

10. DECIBELS:
Range: -20 to +10 dB, -8 to +22 dB,

0 to +30 dB, +6 to +36 dB,
+20 to +50 dB

Reference Level: With zero dB power level equal to 1 mW across

a 600⍀ line.

11. BATTERIES:
Voltage: 1.5V, 9V
NEDA No.: 13F, 1604A

12. FUSE: F1 1A, 250V , type 3A G, quick-acting Littlefuse T ype

312001, F2 2A, 600V Littlefuse Type BLS or
2A 600V, Bussman Type BBS.

13. TEST LEADS: 1 red, 1 black, 48" long.

14. SIZE: 5½” x 7" x 3 “ (13.34 x 17.78 x 7.94 cm)

15. WEIGHT: 3 lbs. (1.359 kg)

16. ***RATED-CIRCUIT
TO-GROUND
VOLTAGE: 1000V AC/DC Max.

9

*Accuracies specified are for the 260 in a horizontal position.
**Responds to the average value of an AC current, and is calibrated to indicate
the RMS value of a pure sine wave.
***Per ANSI C39.5 April 1974: “The specified voltage with respect to ground,
which may be safely and continuously applied to the circuit of an Instrument.”

1.10 Definition of Accuracy

The voltage and current accuracy of this Instrument is commonly expressed as a
percent of full scale. This should not be confused with accuracy of reading (indi­cation). For example, +2% of full scale on the 10 volt range allows an error of
±0.20V at any point on the dial. This means that at full scale, the accur acy reading
would be ±2%, but at half scale it would be ±4%. Therefore, it is advantageous to
select a range which gives an indication as near as possible to full scale.

1.11 Safety Considerations

This Operator’s Manual contains special caution and warning symbols which
alert the user to hazardous operating and service conditions. These symbols
appear throughout this publication where applicable, and are defined on the
inside front cover of this manual under NOTES AND SAFETY INFORMATION.
Please adhere to these instructions to ensure the safety of operating and servic­ing personnel and to retain the operating conditions of the Instrument.

1.12 Audio Alarm

The 260-8P Audio Alarm is a transducer which will emit an audible sound when
the operator of the Instrument intends to quickly determine the continuity of a
circuit.

NOTE: Not protected by Electronic Overload Protection System.

!

Do not make Circuit Continuity Tests with electrical power “ON”. Turn “OFF” all
electrical power.

Table 1-2. Items and Accessories Furnished with This Instrument

Quantity Description Number

1 Test Lead Set - one red and one black (48” long) 00043

each with combination probe tip and removable

rubber-sleeved alligator clip.
*1 1.5 Volt, D Cell, NEDA 13F
*1 9.0 volt Cell, NEDA 1604A
2 1Amp, 250V Fuse, Littlefuse Type #312001
1 2A, 600V Fuse, Littlefuse Type BLS or

(Bussman Type BBS)
1 Operator’s Manual 6-114339

*Batteries are standard items replaceable from local retail stores.

10

Table 1-3. Additional Accessories

Description Catalog No.
Deluxe Case 00812
Leatherette Ever-Redy Hard Case, Drop Front 00805
Model 150-2 Amp-Clamp 00545
Model 151-2 Line Splitter 00544

1.13 Accessory AC High Voltage Probe

The 10,000 volts AC accessory probe is similar to the high voltage DC probes
with the following exceptions: The AC high voltage probe is designed to extend
the 260-8P AC voltage range. The probe can be used with the Simpson 260-8P
10-volt AC range.

NOTE: Instructions are furnished with each high voltage probe.

1.14 Amp-Clamp Model 150-2

The Simpson Amp-Clamp Model 150-2 allows AC current measurements with­out breaking the circuit under test. The Amp-Clamp works as a transformer con­taining a split core for accommodating the conductor which carries the current
being measured. The current-carr ying conductor becomes the transformer pri­mary and a coil in the Amp-Clamp serves as the secondary winding. The Amp­Clamp output voltage is proportional to the current measured and can be applied
to the 260-8P as an AC voltage.

The Amp-Clamp has a range selector with six positions. Any of the following
current ranges can be used with the 260-8P: 5, 10, 25, 50, 100 or 250 amperes.

NOTE: Instructions are furnished with each Amp-Clamp.

2. INSTALLATION

This section contains information and instructions for the installation and ship­ping of the Simpson 260-8P. Included are unpacking and inspection procedures,
warranty, shipping, power source requirements and operating position.

2.1 Unpacking and Inspection

Examine the shipping carton for signs of damage. If damaged, notify the carrier
and supplier and do not attempt further use of the Instrument. If Instrument ap­pears to be in good condition, read Operator’s Manual in its entirety. Become
familiar with the Instrument as instructed in the manual, then proceed to check the
electrical performance as soon as possible. Also, check that all items listed in
Table 1-2 are included with the Instrument.

After unpacking the Instrument, a 1.5V battery and a 9V battery may be found in
separate envelopes in the box with the Instrument and the test leads. Two alliga­tor clips for the test leads are in a polyethylene bag. (See Section 5 for instructions
on how to open the battery compartment and install the batteries.

2.2 Warranty

The Simpson Electric Company warranty policy is printed on the inside front
cover of this manual. Read it carefully before requesting any warranty repairs. For

11

all assistance, including help with the Instrument under warranty, contact the
nearest Authorized Service Center for instructions. If necessary, contact the fac­tory directly, give full details of any installation difficulty and include the Instru­ment model number, series number, and date of purchase. Service data or ship­ping instructions will be mailed promptly. If an estimate of charges for non-war­ranty or other service work is required, a maximum charge estimate will be quoted.
This charge will not be exceeded without prior approval.

2.3 Shipping

Pack the Instrument carefully and ship it prepaid and insured.

2.4 Power Source Requirements

There are two batteries in the ohmmeter circuits, a NEDA 13F D size cell that
furnishes 1.5 volts for the R X 1 and R X 100 ranges and a NEDA 1604A battery
that furnishes 9 volts for the R X 10,000 range. The 1.5 volt D cell is held in place
with two spring clips which also serve as battery contacts. The 9-volt battery is
held in place with a spring clip but contact is made with a separate connector that
is polarized. (Always observe correct polarity when replacing the 1.5-volt D cell.)

2.5 Operating Position

A handle is attached to the side of the Instrument case. The handle may be used
to support the Instrument in a convenient, sloping position for easy viewing. The
VOM case can also be placed either in a vertical or horizontal position. The
horizontal position is preferable for greater accuracy since the Instrument is cali­brated in this position.

3. CONTROLS, JACKS, AND INDICATORS

All operating and adjustment controls, jacks, and indicators for the Simpson 260­8P are illustrated in this section along with a list (Table 3-1) describing their
function. Become familiar with each item before operating the Instrument.

3.1 Front Panel Description

The front panel controls, jacks, and indicators as described in Table 3-1, are
depicted in Figure 3-1.

Table 3-1. Controls, Jacks, and Indicators

1. Front Panel The 260-8P V olt-Ohm-Milliammeter is a large, easy-to-read
4-1/4” indicating Instrument. Below the Instrument are four
controls and eight circuit jacks. Switch positions and circuit
jacks are marked in white characters for easy reading.

2. Range Switch: 12 positions: May be rotated 360° in either direction to
select any of the five AC and DC voltages, four DC cur­rents and three resistance ranges.

12

O

S

M

H

O

H

M

S

.

.C

D

.

.

.C

A

.C

.A

V
.5

2

B

D

7

D

.C

.

A.C

.

6

1

-10 A.

OUTPUT

350 VDC

A.C. VOLTS

ONLY

- D.C.

+ D.C.

3

COMMON

500 MA.

MAX.

2.5 V.
10 V.

1V.

25 V.
50 A.

␮ AMPS.

250 V.

500 V.
I000 V.

+

-

ALL TERMINALS 1 V MAX

100MA.

10MA.
1MA.

R X I00

R x I0,000

260

5

+10A

+1V.

50 ␮ AMPS.
+

250 MV.

ZERO OHMS

AMPS.

R x 1

500 V.

1000 V.

A.C. D.C.

A.C. D.C.

4

2

FIGURE 3-1. Front Panel Controls, Jacks

and Indicators

3. Function Switch: The function switch has four positions: Audio “*”, +DC, -
DC, and AC Volts only. To measure DC current or voltage,
set the function switch at the -DC or +DC position, depend­ing on the polarity of the signal applied across the test
leads. To measure AC voltage set the function s witch to the
AC position. For resistance measurement, the switch may
be set in either the +DC or -DC position. The polarity of the
internal ohmmeter battery voltage will be as marked at the
jacks when the switch is in the +DC position and reversed
in the -DC position.

4. Zero Ohms: This control is used to compensate for variation in the volt­age of the internal batteries, when making resistance mea­surements.

5. Circuit Jacks: There are eight jacks on the front panel marked with the
functions they represent. These jacks provide the electri­cal connections to the test leads. The COMMON (-) jack is
used (in conjunction with the black test lead) as the refer­ence point for the measurement of all the functions with
the exception of the 10 A range. (Refer to Section 4 for
details.)

6. Pointer Adjust

For Zero: With the Volt-Ohm-Milliammeter in an operating position,

check that the pointer indicates zero at the left end of the
scale when there is no input. If pointer is off zero, adjust the
screw located in the cover below the center of the dial. Use
a small screwdriver to turn the screw slowly clockwise or
counterclockwise until the pointer is exactly over the zero
mark at the left end of the scale. With the indicating pointer

13

set on the zero mark, reverse the direction of rotation of the
zero adjuster slightly to introduce mechanical freedom or
“play”, but insufficient to disturb the position of the indicat­ing pointer. This procedure will avoid disturbances to the
zero setting by subsequent changes in temperature, hu­midity, vibration, and other environmental conditions.

7. Reset Button: The white button to the right of the output jack is the reset
button of the overload protection circuit.

4. OPERATION

!

Multifunction instruments (VOMs) such as the 260-8P are intended as general
purpose measuring Instruments for use in low power circuitry such as found in
consumer appliances, TV and radio receivers, and in general laboratory applica­tions. Their use is not recommended in high voltage, high power circuitry where
operator errors and inadequate personal protective measures could result in
serious injury from arcing or explosion. Such circuitry is found in industrial or
commercial applications such as induction (r-f) heaters and broadcast transmit­ters, power substations and distribution centers, X-ray equipment, large motor
controls, etc. Working in the high voltage section of such equipment requires
single-function, often specially designed instruments used by trained personnel
who adopt appropriate protective equipment and procedures.

This section of the manual contains information required to use and operate the
260-8P in a safe and proper manner.

4.1 Safety Precautions

The following precautions are suggestions and reminders of commonly recog­nized safe practices to be adopted and specific hazards to be avoided and are
not implied to be sufficient to safeguard untrained personnel in all circumstances.
Neither is this manual a substitute for technical manuals covering the equipment
in which measurements are to be made. Always refer to the equipment manual
and its specific warnings and instructions and observe them as well as those
contained herein.
a. The 260-8P should only be used by personnel qualified to recognize shock

hazards and trained in the safety precautions required to avoid possible
injury.

b. Do not connect any terminal of this Instrument to a circuit point at which a

voltage exceeding 1000V AC or DC may exist with respect to earth ground.
(Ref. Table 1-1, Item 16.)

c. Tur n off power and discharge any capacitors in the circuit to be measured

before connecting to or disconnecting from it.

d. Before using this Instrument, check accessories (if any) and test leads for

missing, damaged, deteriorated or otherwise faulty insulating parts. Do not
use, or permit the use of equipment with faulty insulation until it has been
properly repaired.

e. Always wear safety glasses when working with electrical circuitry.

14

f. Do not work alone on high voltage circuits. Make certain that someone ca-

pable of giving aid is nearby and alert.

g. Do not handle the Instrument, its test leads, or the circuitry while high voltage

is being applied.

h. Hands, shoes, floor, and workbench must be dry. Avoid making measure-

ments under humid, damp, or other environmental conditions that could
effect the dielectric withstanding voltage of the test leads or Instruments.

i. Do not change switch settings or test lead connections while the circuit is

energized. A mistake could result in damage to the Instrument and personal
injury.

j. Locate all voltage sources and accessible current paths before making con-

nections to circuitry. High voltages may appear unexpectedly or in unex­pected locations in faulty equipment. An open bleeder resistor, for example,
may result in a capacitor retaining a dangerous charge.

k. Make certain that the equipment being worked upon is properly grounded

and fuses are of the proper type and rating.

l. Double check switch positions and jack connections before applying power

to the Instrument.

m. Remain alert for low voltage circuits which may be floating at high voltage

with respect to earth ground and for composite voltages (AC + DC) such as
are found in r-f amplifiers. The floating voltage or composite voltage must not
exceed the Instruments rated maximum circuit-to-ground voltage.

n. Do not make electrical measurements where the air may contain explosive

concentrations of gas or dust such as in mines, grain elevators, gasoline
stations or in the presence of charging batteries until determined to be safe
by qualified personnel. Note that even metallic dusts can be explosive.

o. No General Purpose VOM is to be used to make electrical measurements on

blasting circuits or blasting caps.

4.2 Polarity Re ver sing

The function switch provides a convenient means to reverse polarity of the inter­nal battery to facilitate testing semiconductor devices. The +DC and -DC posi­tions transpose internal connections to the COMMON and +jacks and therefore
can also be used to reverse polarity of external voltages and currents connected
to these jacks (only). Because polarity reversing momentarily interrupts the cir­cuit, it should not be done while measuring current or voltage without first turning
off the circuit power. When making measurements on the 50µA/250mV, 1 volt, or
10 amp range, polarity can be corrected only by reversing the test leads.

4.3 Measurement of Unknown Voltage or Current

Sometimes the approximate voltage or current to be measured is known and the
correct range may easily be selected. It is often the case, however, particularly
when working upon faulty equipment, when the voltage or current is either un­known or may be much higher than normal and anticipated. Whenever working
upon unfamiliar or unknown equipment, always begin a measurement using the
highest range available on the Instrument. Once it is determined that the voltage
is within the limits of a lower range, change to the lower range.

15

4.4 Test Leads

Test leads are provided with accessor y screw-on alligator clips which may be
attached to the probe tips. Eliminating the need to hand-hold test prods to a circuit
for extended periods, the test clips also reduce hand proximity to a high voltage
circuit while energized. Circuit power must of course be turned off and any charged
capacitors discharged before connecting or disconnecting clips to or from the
current.

4.5 DC V oltage Measurement

!

Before making voltage measurements, re vie w the SAFETY PRECAUTIONS listed
in paragraph 4.1. Also, when using the 260 as a millivoltmeter, take care to pre­vent damage to the indicating instrument from excessive voltage.

4.5.1 DC Voltage Measurement 0-250 mV Range

Before using the 250 millivolt range, use the 1.0-volt DC range to determine that
the voltage measured is not greater than 250 millivolts (or .25 volt DC).

a. Set the function switch at +DC (Figure 4-1).
b. Plug the black test lead in the -COMMON jack and the red test lead into the

+50µAmps/250mV/10A jack.
c. Set the range switch at 50 µAmps (COMMON) position with 50V.
d. Connect the black test lead to the negative side of the circuit being measured

and the red test lead to the positive side of the circuit.
e. Read the voltage on the black scale marked DC and use the figures marked

0-250. Read directly in millivolts.

NOTE: For polarity reversing see paragraph 4.2.

4.5.2 DC Voltage Measurement 0-1V Range

a. Set the function switch at +DC (Figure

4-1).

b. Plug the black test lead into the -COM-

MON jack and the red test lead into

the +1V jack.

c. Set the range switch at 1V (COMMON

position with 10V).

d. Connect the black test lead to the nega-

tive side of the circuit being measured

and the red test lead to the positive

side of the circuit.

e. Read the voltage on the black scale

marked DC and use the figures

marked 0-10. Then divide the reading

by 10.

NOTE: For polarity reversing see para-

graph 4.2.

16

- D.C.

- D.C.

+ D.C.

+ D.C.

COMMON

-

Figure 4-1. Jacks and Switch
Positions for Measuring DC Voltages,
0 through 1V Ranges

.

.C

D

10 V.

1V.

50 A.

␮ AMPS.

+

260

ALL TERMINALS 1 V MAX

D

.C

.

+10A

+1V.

50 ␮ AMPS.

+

250 MV.

4.5.3 DC Voltage Measurement 0-2.5 Through 0-250V Range

a. Set the function switch at +DC (Figure

4-2).
b. Plug the black test lead into the -COM-

MON jack and the red test lead into

the + jack.
c. Set the range switch at one of the five

voltage range positions marked 2.5V,

.

.C

D

10V, 25V , 50V or 250V.
NOTE: When in doubt as to the voltage

present, always use the highest voltage
range as a protection to the Instrument. If
the voltage is within a lower range, the
switch may be set for the lower range to
obtain a more accurate reading. Be sure
power is off in the circuit being measured
and all capacitors discharged.

d. Connect the black test lead to the nega-

- D.C.

+ D.C.

COMMON

2.5 V.
10 V.

1V.

25 V.
50 A.

␮

AMPS.

250 V.

500 V.
I000 V.

+

-

260

ALL TERMINALS 1 V MAX

tive side of the circuit being measured

and the red test lead to the positive

side of the circuit.
e. Turn on the power in the circuit being

measured.

Figure 4-2. Jacks and Switch
Positions for Measuring DC
Voltages, 0-250V Range

f. Read voltage on the black scale

marked DC. For the 2.5V range, use the 0-250 figures and divide by 100. For

the 10V, 50V, and 250V ranged, read the figures directly. For the 25V range,

use the 0-250 figures and divide by 10.
NOTE: Turn off power to the circuit and wait until the meter indicates zero before

disconnecting the test leads.

D

50 ␮ AMPS.

+

.C

.

+10A

250 MV.

4.5.4 DC Voltage Measurement 0-500V Range

!

Use extreme care when working with high
voltage circuits. Do not touch the Instrument
or test leads while power is on in the circuit
being measured.

Before proceeding with the following steps,
review the Safety Precautions in Paragraph

4.1.
a. Set the function switch at +DC (Figure

4-3).
b. Set the range switch at the 250V/550V/

1000V Position.
c. Plug the black test lead into the -COM-

MON jack and the red test lead into the

500V jack.
d. Be sure power is off in the circuit being

measured and all capacitors dis-

17

.

.C

D

- D.C.

+ D.C.

COMMON

-

Figure 4-3. Jacks and Switch
Positions for Measuring DC
Voltages, 0-500V Range

250 V.

500 V.
I000 V.

ALL TERMINALS 1 V MAX

D

.C

.

1000 V.

260

A.C. D.C.

charged. Connect the black test lead to the negative side of the circuit being

measured and the red test lead to the positive side of the circuit.
e. Turn on power in circuit being measured.
f. Read the voltage using the 0-50 figures on the black scale marked DC.

Multiple the reading by 10.
NOTE: Turn off power to the circuit and wait until the meter indicates zero before

disconnecting the test leads.

4.5.5 DC Voltage Measurement 0-1000V Range

!

Use extreme care when working with high voltage circuits. Do not touch the
Instrument or test leads while power is on in the circuit being measured.
Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.1.
a. Set the function switch at +DC (Figure

4-4).
b. Set the range switch at the 250V/500V/

1000V Position.
c. Plug the black test lead into the -COM-

MON jack and the red test lead into

the 1000V jack.
d. Be sure power is off in the circuit be-

ing measured and all capacitors dis-

charged. Connect the black test lead

to the negative side of the circuit be-

ing measured and the red test lead to

the positive side of the circuit.
e. Tur n on power in circuit being mea-

sured.
f. Read the voltage using the 0-10 fig-

ures on the black scale marked DC.

Multiple the reading by 100.
NOTE: T urn off power to the circuit and wait

until the meter indicates zero before

disconnecting the test leads.

.

.C

D

- D.C.

+ D.C.

COMMON

250 V.

500 V.
I000 V.

-

260

ALL TERMINALS 1 V MAX

Figure 4-4 Jacks and Switch
Positions for Measuring DC
Voltages, 0-1000V Range

D

.C

1000 V.

A.C. D.C.

.

4.6 AC Voltage Measurement

!

Branch and distribution circuits (120/240/480V etc.) can deliver dangerous ex­plosive power momentarily into a short circuit before the fuse/breaker opens the
circuit. Make certain that the Instrument switches are set properly, jacks are con­nected properly, and that the circuit power is turned off before making connec­tions to such circuits.

The 260 responds to the average value of an AC waveform. It is calibrated in
terms of the RMS value of a pure sine wave. If the waveform is nonsinusoidal, and

18

depending upon its waveform, the reading may be higher or lower than the true
RMS value of the measured voltage. Thus an error may be introduced if the 260
is used to measure a nonsinusoidal waveform. Also, accuracy is lessened at
higher input frequencies (Figure 4-5).

4.6.1 AC Voltage Measurement 0-2.5 Thru 0-250V Range

Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.1.

a. Set the function switch at AC

Volts Only position (Figure 4-6).

NOTE: The meter will not indicate if

the switch is incorrectly set to a

DC position.

b. Set the range switch at one of the

five voltage range positions

marked 2.5V, 10V, 50V or 250V.

(When in doubt as to actual volt-

age present, always use the

highest voltage range as a pro-

tection to the Instrument. If the

voltage is within a lower range,

the switch may be set for the

lower range to obtain a more ac-

curate reading.)

c. Plug the black test lead into the -

COMMON jack and the red test

lead into the + jack.

d. Turn off power to the circuit to be

measured and discharge any ca-

pacitors.

e. Connect the test leads across the

circuit voltage to be measured

with the black lead to the

grounded side.

f. For the 2.5V range read the value

directly on the scale marked 2.5V

AC. For the 10V, 25V, 50V and

250V ranges, read the red scale

marked AC and use the black fig-

ure immediately above the scale.

+6

+5
+4

+3

+2

+1

-1

-2

PERCENT RELATIVE ERROR

-3

-4

-5

AC VOL TAGE RANGES

2.5 VAC RANGE
10VAC RANGE

25 VAC RANGE

50 VAC RANGE
250 VAC RANGE
500 VAC RANGE

1000 VAC RANGE

0

10Hz 100Hz 1KHz 10KHz 100KHz 1MHz

FREQUENCY

Figure 4-5, Frequency Response
AC Voltage Ranges

.

.C

A

.C.

2.5 V.A

A.C . VOLT S

ONLY

2.5 V.
10 V.

1V.

25 V.
50 A.

␮ AMPS.

250 V.

500 V.
I000 V.

COMMON

+

-

260

ALL TERMINALS 1 V MAX

Figure 3-1. Fro

A.C.

Figure 4-6. Jacks and Switch
Positions for Measuring AC Voltages,
0-2.5 through 0-250V Ranges

19

4.6.2 AC Voltage Measurement 0-500V Range

!

Do not attempt any voltage measurement which may exceed 1000 volts or the
circuit-to-ground voltage of the Instrument, 1000 volts maximum.

Be sure that the range switch is set to the 250V/500V/1000V range, function
switch to AC Volts Only position, and test leads connected to common and 500V
jack.

Do not touch the Instrument or test leads while the power is on the circuit being
measured.

Use extreme care when working in high voltage circuits. Do not handle the Instru­ment or test leads while the circuit being measured is energized. OBSERVE ALL
SAFETY PRECAUTIONS in paragraph 4.1 and in the instruction manual for the
equipment being tested.
Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.2.

a. Set the function switch at AC Volts

Only position. (Figure 4-7).

NOTE: The meter will not indicate if the

switch is incorrectly set to a DC po­sition.

b. Set the range switch at the 250V/

500V/1000V position.

c. Plug the black test lead into the -

COMMON jack and the red test lead
into the 500V jack.

d. Be sure the power is off in the circuit

being measured and that all its ca­pacitors have been discharged.

e. Connect the test leads across the

circuit voltage to be measured with
the black lead to the grounded side,
if any.

f. Turn on the power in the circuit be-

ing measured.

g. Read the voltage on the red scale

marked AC. Use the 0-50 figures and
multiply by 10.

.

.C

A

2.5 V.A.C.

A.C. VOLTS

ONLY

2.5 V.
10 V.

1V.

25 V.
50 A.

␮ AMPS.

250 V.

500 V.
I000 V.

COMMON

-

260

ALL TERMINALS 1 V MAX

Figure 4-7. Jacks and Switch
Positions for Measuring AC Voltage,
0-500V Range

A.C. D.C.

A.C.

500 V.

4.6.3 AC Voltage Measurement 0-1000V Range

!

Use extreme care when working in high voltage circuits. Do not handle the Instru­ment or test leads while the circuit being measured is energized. OBSERVE ALL
SAFETY PRECAUTIONS in paragraph 4.1 and in the instruction manual for the
equipment being tested.

Do not attempt any voltage measurement which may exceed 1000 volts or the
circuit-to-ground voltage of the Instrument, 1000 volts maximum.

20

Be sure that the range switch is set to the 250V/500V/1000V range, function
switch to AC position, and test leads connected to common and 1000V jack.

Do not touch the Instrument or test leads while the power is on in the circuit being
measured.

Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.2.

a. Set the function switch at AC Volts
Only position. (Figure 4-8).

NOTE: The meter will not indicate if the
switch is incorrectly set to a DC position.
b. Set the range switch at the 250V/500V/

1000V position.

c. Plug the black test lead into the -COM-

.

.C

A

.C.

2.5 V.A

A.C.

MON jack and the red test lead into
the 1000V jack.

d. Be sure power is off in the circuit be-

ing measured and that all its capaci­tors have been discharged.

e. Connect the test leads across the cir-

cuit voltage to be measured with the
black lead to the grounded side.

f. Turn on the power in circuit being mea-

A.C . VOLT S

ONLY

COMMON

250 V.

500 V.
I000 V.

-

260

ALL TERMINALS 1 V MAX

1000 V.

A.C. D.C.

sured.

g. Read the voltage on the red scale

marked AC. Use the 0-10 figures and
multiply by 100.

Figure 4-8. Jacks and Switch
Positions for Measuring
AC Voltage, 0-1000V Range

4.7 Output V oltage Measurement

Certain situations necessitatethe measuring of the AC component of an Output
Voltage where both AC and DC voltage levels exist. This occurs primarily in
amplifier circuits. The 260-8P has a 0.1 mfd, 400 volt capacitor in series with the
OUTPUT jack. The capacitor blocks the DC component of the current in the test
circuit, but allows the AC or desired component to pass on to the indicating
instrument circuit. The blocking capacitor may alter the AC response at low fre­quencies but is usually ignored at audio frequencies (Figure 4-9).

Do not connect the OUTPUT jack to a circuit in which the DC voltage component
exceeds 350V.
Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.1.
a. Set the function switch at AC Volts Only position. (Figure 4-10).
b. Plug the black test lead into the -COMMON jack and the red test lead into the

OUTPUT jack.

c. Set the range switch at one of the range positions marked 2.5V, 10V, 25V,

50V, or 250V.

d. Connect the test leads across the circuit being measured with the black test

lead to the grounded side.

21

A.C. VOLTS

ONLY

COMMON

+10

+8

.

.C

A

2.5 V.A.C.

OUTPUT

350 VDC

500 MA.

MAX.

2.5 V.
10 V.

1V.

25 V.
50 A.

␮ AMPS.

250 V.

500 V.
I000 V.

-

260

ALL TERMINALS 1 V MAX

A.C.

+6

+4

+2

0

-2

-4

-6

-8

-10

10Hz 100Hz 1KHz 10KHz 100KHz 1MHz

OUTPUT RANGES

2.5 VAC RANGE
10VAC RANGE

25/50 VAC RANGE

250 VAC RANGE

FREQUENCY

Figure 4-10. Jacks and Switch
Positions for Output Measurements

Figure 4-9. Frequency Response
Output Ranges

e. T urn on the power in the test circuit. Read the output voltage on the appropri-

ate AC voltage scale. For the 0-2.5V range, read the value directly on the
scale marked 2.5V AC. For the 10V, 25V, 50V, or 250V ranges, use the red
scale marked AC and read the black figures immediately above the scale.

4.8 Decibel Measurement (-20 To +50 dB)

Some industries measure in terms of voltage or current ratios (decibels) based
on a specific reference level. The dB scale on the 260-8P serves this purpose and
is calibrated to a reference level (zero dB) or 0.001 watt into 600 ohms. The scale
calibration of -20 to +10 dB is for the 0-2.5V range (zero dB = 0.775V). Higher
ranges may be used by adding an appropriate dB value to the reading in accor­dance with the chart below.

a. Review the safety precautions in paragraph 4.1.
b. Refer to Figure 4-11 for switch settings and jack connections.
c. Use operating instructions for AC VOLTAGE MEASUREMENT,

0-2.5/10/25/50/250V RANGES (paragraph 4.6.1).

Do not use the 500V or 1000V ranges for decibel readings.

d. Read decibels on the bottom scale marked dB. For the 10/25/50/250V ranges,

add the appropriate factor from the following chart:

EGNAREGATLOVEGNARBdGNIDAER

V5.2-001+ot02-yltceriddaer
V01-022+ot8-gnidaerotBd21+dda
V52-003ot0gnidaerotBd02+dda
V05-063+ot6+gnidaerotBd62dda

V052-005+ot02+gnidaerotBd04dda

22

NOTE: The maximum v oltage ratio that can be measured is +50 dB on the 0-250V

range.
e. If dB measurements are being made to a 0.006 watt into 500 ohm reference

level, subtract +7 dB from the reading obtained on the 260.

4.9 Direct Current Measurement

!

a. Do not change the range setting of

the range or function switches while
the circuit is energized.

b. Never disconnect test leads from the

circuit under measurement while it
is energized.

c. Always turn the power off and dis-

charge all the capacitors before the
setting of the switches is changed,
or the leads disconnected.

d. Never exceed the circuit-to-ground

voltage of the instrument (1000V
Max., Table 1-1, Item 16).

e. Always connect the instrument in se-

ries with the ground side of the cir­cuit.

f. In all direct current measurements,

make certain the power to the circuit
being tested has been turned off be­fore connecting and disconnecting
test leads or restoring circuit conti­nuity.

A.C . VOLT S

Figure 4-11. Jacks and Switch
Positions for Measuring Decibels

ONLY

COMMON

B

D

500 MA.

2.5 V.
10 V.

1V.

25 V.
50 A.

␮ AMPS.

250 V.

500 V.
I000 V.

+

-

260

ALL TERMINALS 1 V MAX

4.9.1 Direct Current Measurement 0-50µA Range

a. Set the function switch at +DC.
b. Plug the black test lead into the -COMMON jack and the red test lead into the

+50µAMPS/250mV jack.
c. Set the range switch at 50µAMPS (dual position with 50V).
d. Open the ground side of the circuit in which the current is being measured.

Connect the VOM in series with the circuit. Connect the red test lead to the

positive side and the black test lead to the negative side.
e. Read the current on the black DC scale. Use the 0-50 figures to read directly

in microamperes.

NOTE: For polarity reversing see paragraph 4.2.

4.9.2 Direct Current Measurement 0-1mA Through 0-500mA
Range

a. Set the function switch at +DC (Figure 4-12).
b. Plug the black test lead into the -COMMON jack and the red test lead into the

+ jack.

c. Set the range switch at one of the four range positions marked 1 mA, 10 mA,

100 mA or 500 mA

23

d. Open the grounded side of the circuit in which the current is being measured.

Connect the VOM in series with the circuit. Connect the red test lead to the
positive side and the black test lead to the negative side.

e. Turn the power on. Read the current in milliamperes on the black DC scale.

For the 1 mA range, use the 0-10 figures and divide by 10. For the 10 mA
range, use the 0-10 figures directly. For the 100 mA range, use the 0-10
figures and multiply by 10. For the 500 mA range, use the 0-50 figures and
multiply by 10.

f. Turn the power off and disconnect the test leads.

!

This range is only intended for measurements in low voltage circuits (under 25V
DC) such as the primary power in vehicles or their accessories.

4.9.3 Direct Current Measurement 0-10A Range

a. Plug the black test lead into the -10A

jack and the red test lead into the +10A
jack.

b. Set the range switch at 10 AMPS (dual

position with 10 mA).

c. Open the grounded side of the circuit

in which the current is being mea­sured. Connect the VOM in series with
the circuit, connecting the red test lead
to the positive side and the black test
lead to the negative side.

NOTE: The function switch has no effect

on polarity for the 10 AMPS range.

d. Turn the power on. Read the current

directly on the black DC scale. Use the
0-10 figures to read directly in am­peres.

e. Turn the power off and disconnect the

test leads.

.

.C

D

-10 A.

COMMON

500 MA.

50 A.

␮ AMPS.

+

-

- D.C.

+ D.C.

260

ALL TERMINALS 1 V MAX

100MA.

10MA.

AMPS.

1MA.

Figure 4-12. Jacks and Switch
Positions for Measuring Direct
Current

!

The 10A range is not internally fused in the 260-8P.
When using the 10A range, never disconnect a test lead from a jack or from the

circuit while the circuit is energized. Doing so may damage the test jacks or leads
and the arcing may be hazardous to the operator. Turn off circuit power and wait
for the meter reading to drop to zero.

The polarity reversing feature of the function switch does not operate on the 0­10A range. If polarity is found to be incorrect, turn off circuit power, wait for the
meter indication to reach zero and then interchange test lead connections to the
circuit.

D

.C

.

+10A

50 ␮ AMPS.

+

250 MV.

24

4.10 Resistance Measurements

!

Voltage applied to a resistance range will cause reading errors if low and dam­age the Instrument if high. When making in-circuit measurements, make certain
that the circuit is completely de-energized before making connections to it.

When making in-circuit measurements, circuit paths in parallel with the resis­tance being measured may cause reading errors. Check circuit diagrams for the
presence of such components before assuming that the reading obtained is
correct.

When resistance is measured, the batteries furnish power for the circuit. Since
batteries are subject to variation in voltage and internal resistance, the Instru­ment must be adjusted to zero before measuring a resistance, as follows:
a. Turn range switch to desired ohms range.
b. Plug the black test lead into the -COMMON jack and the red test lead into the

+ jack.

c. Connect the ends of test leads together to short the VOM resistance circuit.
d. Rotate the ZERO OHMS control until pointer indicates zero ohms. If pointer

cannot be adjusted to zero, one or both of the batteries must be replaced.
(For battery replacement, refer to Section 5.)

e. Disconnect shorted test leads.

4.11 Measuring Resistance

a. Before measuring resistance in a circuit, make sure the power is off to the

circuit being tested and all capacitors are discharged. Disconnect shunting
components from the circuit before measuring its resistance.

b. Set the range switch to one of the resistance range positions as follows

(Figure 4-13):

1. Use R X 1 for resistance readings from 0 to 200⍀.

2. Use R X 100 for resistance readings from 200 to 20,000⍀.

3. Use R X 10,000 for resistance readings above 20,000⍀.

c. Set the function switch at either -DC or +DC position: Operation is the same

in either position except if there are semiconductors in the circuit. (See para­graph 4.12.) Adjust ZERO OHMS control for each resistance range.

d. Observe the reading on the OHMS scale at the top of the dial.

NOTE: The OHMS scale reads from right to left for increasing values of resis-

tance.
e. T o determine the actual resistance value , m ultiply the reading by the f actor at

the switch position. (K on the OHMS scale equals one thousand.)

4.12 Resistance Measurement of Semiconductors

Make sure that the OHMS range being used will not damage any of the semicon­ductors (refer to Table 1-1, item 8, Section 1).

If there is a “forward” and “backward” resistance such as in diodes, the resistance
should be relatively low in one direction (for forward polarity) and higher in the
opposite direction.

25

Rotate the function switch between the two
DC positions to reverse polarity. This will
determine if there is a difference between
the resistance in the two directions.

S

M

H

O

OHMS

To check a semiconductor in or out of a
circuit (forward and reverse bias resistance
measurements) consider the following

fore

making the measurement:

be-

a. The polarity of the internal ohmmeter

battery voltage will be as marked at
the jacks when the switch is in the +DC
position and reversed in the -DC posi­tion.

b. Ensure that the range selected will not

damage the semiconductor. (Refer to
T able 1-1, item 8, and re view the speci-

- D.C.

+ D.C.

COMMON

+

-

260

ALL TERMINALS 1 V MAX

R X I00

R x I0,000

ZERO OHMS

R x 1

fication limits of the semiconductor ac­cording to the manufacturer’s ratings.)

c. If the semiconductor is a silicon diode

Figure 4-13. Jacks and Switch
Positions for Measuring Resistance

or conventional silicon transistor, pre­cautions are not normally required.

d. If the semiconductor material is germanium, check the ratings of the device

and refer to Table 1-1, item 8.

NOTE: The resistance of diodes will measure differently from one resistance

range to another on the VOM with the function switch in a given position. For
example, a diode which measures 80 ohms on the R X 1 range may mea­sure 300 ohms on the R X 100 range. The difference in values is a result of
the diode characteristics and is not indicative of any fault in the VOM.

4.13 Continuity Tests

!

Tur n off all power to the circuit under test
before proceeding any further.

a. Set the FUNCTION switch to the “*”.

Insert the black test lead into the COM­MON (-) and the red test lead into the
(+) jacks, (Figure 4-14).

b. Touching the test lead probe tips to-

gether should produce an audible
sound

c. To test for continuity, probe the circuit

or component in question. An audible
sound indicates continuity.

d. The higher the circuit’s resistance, the

lower the sound level. The lower the
circuit’s resistance, the higher the
sound level.

e. Refer to Paragraph 4.12, Figure 4-13

for measurements of circuit resistance, if any, that exists.

26

R X I00

R x I0,000

OHMS

ZERO OHMS

R x 1

S

M

H

O

- D.C.

+ D.C.

COMMON

+

-

260

ALL TERMINALS 1 V MAX

Figure 4-14. Jacks and Switch

Positions for Continuity Tests

5. OPERATOR MAINTENANCE

The following paragraphs of this section describe battery replacement, fuse re­placement, and preventive maintenance procedures for the 260.

5.1 Inspection

The user is protected from electrical shock by the insulation of the 260 and its test
leads. Frequently examine them for any insulation damage such as cracks, cuts,
chips, burns or deterioration that expose internal metal parts or reduce the spac­ing between such metal parts and hand contact by the operator.

Make certain that the battery compartment cover is securely fastened in place
before the Instrument is used.

Do not permit an instrument with a broken meter glass to be used.
Whenever the battery compartment cover is removed for any reason, check that

the proper fuses are being used.

5.2 Battery Replacement

a. Two batteries are used inside the case to supply power for resistance mea-

surements. One is a 1.5-v olt D cell and the other is a 9 v olt battery. When it is
no longer possible to adjust the pointer to zero for the R X 1 and R X 100
ranges (refer to ZERO OHMS ADJUSTMENT paragraph 4.21) replace the

1.5 volt cell. When it is no longer possible to adjust the pointer to zero on the
R X 10,000 range, replace the 9 volt battery.

b. Recommended replacement batteries are:

1.5V D cell, NEDA 13F (Duracell MN or Eveready No. 95). 9V battery, NEDA
1604A (Duracell MN1604 or Eveready 522).

c. To install or replace a battery , de-energize and disconnect test leads from the

Instrument, then remove the cover to the externally accessible battery com­partment by loosening the single captivated screw.

NOTE: Batteries should be replaced before their useful life has e xpired. Failure to
do so may result in corrosion and battery leakage.

d. Observe polarity when replacing the 1.5 volt D cell and connect as indicated.

The D cell is held in place with spring clips which also act as battery contact
clips. The 9 volt battery contacts and connector are polarized. To remove the
9 volt battery, first withdraw battery with mated connector from the compart­ment. Then remove the connector.

5.3 Fuse Replacement

The 1 and 2 ampere fuse (also the 1A spare) is located in the externally acces­sible battery and fuse compartment. Access to the compartment is obtained by
disconnecting the test leads and loosening the single captivated screw on the
compartment cover. To replace or check a fuse: Apply pressure to the 1 amp fuse
cup then rotate the plate to expose a selected fuse for removal from the panel’s
cavity.

NOTE: When you replace a fuse, make sure it is the same type and value as the
fuse you have just removed.

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5.4 T est Lead Inspection

Periodic inspection of the test leads is recommended to detect cuts, burned areas,
rioration or other damage that could reduce the insulation strength of leads.

5.5 Care

a. Immediately clean all spilled materials from the Instrument and wipe dr y. If

the spillage is corrosive, use a suitable cleaner to neutralize the corrosive
action.

b. When Instrument is not in use, rotate the function switch to the +DC position.
c. Avoid prolonged exposure or usage in areas which are subject to tempera-

ture and humidity extremes, vibration or mechanical shock, dust or corrosive
fumes, or strong electrical or electromagnetic interferences.

d. Verify Instrument accuracy by performing operational checks using known,

accurate, stable sources. If proper calibration equipment is not available,
contact the nearest Authorized Service Center. If the Instrument has not been
used for 30 days, check the batteries for leakage and replace if necessary.

e. It is recommended that the Instrument be returned annually to the nearest

Authorized Service Center, or to the factory, for an overall chec k, adjustment,
and calibration.

f. When the Instrument is not in use, store it in a room free from temperature

extremes, dust, corrosive fumes, and mechanical vibration or shock. If stor­age time is expected to exceed 30 days, remove batteries.

dete-

Figure 5-1. Battery and Fuse
Compartment

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NOTES

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NOTES

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SIMPSON ELECTRIC COMPANY 853 Dundee Avenue

Elgin, IL 60120-3090 [phone] FAX [phone]
Printed in U.S.A. Part No. 06-114339 Edition 8, 12/01

Visit us on the web at: www.simpsonelectric.com

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