Simpson Electric 444 Instruction Manual

Model 444

Digital Micro-Ohmmeter

OPERATOR’S 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 symbols 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 which is used carelessly. Therefore, this manual must be read carefully
and completely before making any measurements. Failure to follow direc­tions can result in a serious or fatal accident.

Technical Assistance

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

Warranty and Returns

SIMPSON ELECTRIC COMP ANY warr ants 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 defective; 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.

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This Instrument is designed to prevent accidental shock to the operator when
properly used. However, no engineering design can render safe an instru­ment which 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 IEC-1010-1 Safety Requirements for Elec­trical Measurement, Control and Laboratory Use, 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 MIU (Measure Indication Units) when measured
with an appropriate measurement instrument as defined in Section 6.3.1.2
Annex A of IEC-1010-1.

NOTE: UL-1244 calls for the same voltage and measurement limits as IEC­1010-1:1990 but UL-1244 specifies a slightly different test network. Simpson
Electric manufactures test equipment to measure shock hazard as set forth
by both specifications. The Simpson Model 228 uses the networks specified
by IEC-1010-1 and is suitable for measuring shock hazard as defined in that
document. The Simpson 229-2 uses the measurement networks specified in
UL-1244 and is suitable for measuring shock hazard as defined in that
document.

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Contents

1. INTRODUCTION................................................................................ 5

1.1 Items And Accessories .......................................................................5

1.2 Safety Considerations ........................................................................5

1.3 Technical Data Specifications ............................................................ 5

2. INSTALLATION.................................................................................. 6

2.1 Unpacking And Inspection .................................................................6

2.2 Warranty..............................................................................................7

2.3 Shipping .............................................................................................7

2.4 Power Source Requirements ............................................................. 7

2.5 How to Position Instrument While Operating......................................7

3. CONTROLS , CONNECTORS & INDICA T ORS ................................... 7

3.1 Front Panel Description ...................................................................... 7

4. OPERATION...................................................................................... 8

4.1 Safety Precautions .............................................................................. 9

4.2 Operating Instructions ........................................................................ 9

4.2.1 AC Measurement Mode ................................................................... 10

4.2.2 DC Measurement Mode ................................................................... 10

4.2.3 User Settable Continuity .................................................................. 10

5. THEOR Y OF OPERATION .............................................................. 11

5.1 Theory Of Measurement...................................................................1 1

6. OPERATOR MAINTENANCE .......................................................... 12

6.1 Cover Removal .................................................................................13

6.2 Battery Replacement ........................................................................13

6.3 Fuse Replacement ...........................................................................13

6.4 Preventive Maintenance ...................................................................14

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1. INTRODUCTION

The Simpson 444 Micro-Ohmmeter measures resistances from 1 micro-ohm
to 20 ohms. It measures by using a small test voltage (100 microvolt maxi­mum) and a 4 wire measurement technique. The measured resistance is dis­played on 4-1/2 digit LCD display. The 444 is designed to be run from the
power line, but self-contained rechargeable Ni-Cad batteries are provided
for field use.

The Simpson 444 has two measurement modes, an automatic AC measure­ment mode and a manual DC measurement mode. In the AC mode a 100
microvolt maximum square wave is used to test the resistance. Because of
the AC nature of the square wave, all offset voltages and thermocouple ef­fects are automatically canceled and the resistance can be directly read. In
the DC mode, a 100 microvolt maximum DC test voltage is used and the user
must manually cancel out any offsets and thermocouple effects.

1.1 Items And Accessories

All items and accessories required for the operation of the 444 are furnished
with each Instrument, and listed in Table 1-2.

1.2 Safety Considerations

This Operator’s Manual contains cautions and warnings alerting the user to
hazardous operating and servicing conditions. This information is flagged by
CAUTION or WARNING symbols throughout this publication, where appli­cable, and is defined on the inside front cover of this manual under SAFETY
SYMBOLS. To ensure the safety of operating and servicing personnel and to
retain the operating conditions of this Instrument, please adhere to these in­structions.

1.3 T echnical Data Specifications

Table 1-1 lists the technical data for the 444 Digital Micro-Ohmmeter.

Table 1-1. Technical Data

The following specifications apply over an operating temperature range of
18° to 28°C and at a relative humidity up to 80% unless otherwise specified.

1. Accuracy: AC MODE: ⫾(0.05% of input + 15 counts)
DC MODE: ⫾(0.05% of input + 600 counts)

2. Maximum Test V oltage: 100µV (Peak)

3. Measurement Techniques:

Pulse (AC) 40 Hertz Square Wave
DC Switchable Polarity

4. Alarm: Resistance below setpoint activates audible

beeper and display annunciator. Resistance
above setpoint activates display annunciator.

Setpoint Adjustment Front Panel Knob

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