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Hewlett Packard 428A Analog multimeter
Manufacturer:
Model:
428A
Date:
1960
Class:
Type:
SubType:
Clip-On Milliammeter

Information

For a long time the design engineer in the laboratory or the technician in the iield has been in need of an instrument that would measure dc currents without breaking the leads. Since the introduction of the transistor, which is a current device, the need for a fast, convenient method for measuring dc currents became even more apparent. The Model 428A Clip-On Milliammeter realizes the above stated objectives in a unique way. The instrument measures the magnetic field, which exists around the wire carrying dc current. Operating the instrument is simple. After zero setting, the two jaws of the Probe are clamped around wire (arrow on Probe head indicates direction of conventional current flow) and the meter will indicate the current. There are six current ranges starting from 3 ma to 1000 ma full scale deflection. The sensitivity can be increased even further by looping the wire several times through the opening in the Probe. For example, three turns increase the maximum sensitivity to 1 ma full scale. The current indication is virtually insensitive to superimposed ac signals and the series loading of the circuit is less than 0.5 ┬Áh. A large amount of feedback provides great stability. With the 428A currents can be measured as easily as measuring voltages with a voltmeter.

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Service and User Manual
Manual type:
Service and User Manual
Pages:
47
Size:
4.84 Mbytes (5070453 Bytes)
Language:
english
Revision:
Manual-ID:
Date:
01 September 1960
Quality:
Scanned document, all readable.
Upload date:
31 May 2020
MD5:
28e45eab69f11dabb17c893f03c80b2c
Downloads:
23

Information

Serial Prefixed 022- SECTION I GENERAL 1-1 Introduction ... I - 1 1-2 Installation ... I - 1 1-3 Three Conductor Power Cable ... I - 1 1 - 4 230-Volt Operation . ... I - 1 SECTION II OPERATION 2-1 Turn-On Procedure ... . . II - 1 2-2 Mechanical Operation of Probe ... ... II - 1 2-3 Electrical Zero Set ... ... II - 1 2-4 Degaussing of Probe Head ... 2-5 Measurement Precautions ... ... II - 1 2-6 Measurement Practices ... ... II - 3 2-7 Operation with Graphic Recorder ... ... II - 3 SECTION III THEORY 3 - 1 3 - 2 3-3 Introduction ... Overall Operation ... Current Probe ... ... Ill - 1 ... Ill - 1 3-4 20 KC Oscillator ... ... Ill - 2 3-5 20 KC Head-Drive Amplifier ... ... Ill - 2 3 - 6 40 KC Synchronous Detector/Amplifier ... ... Ill - 3 3-7 40 KC Input/Amplifier Circuit ... . ... Ill - 3 3-8 40 KC Synchronous Detector and Filter (C16) ... ... Ill - 3 3-9 DC Amplifier ... 3-10 3-11 40 KC Phase Shifter ... ... Ill - 5 3-12 Power Supply ... SECTION IV MAINTENANCE 4-1 Introduction ... IV - 4-2 Mechanical Zero-Set ... IV - 4-3 Cleaning of Probe Jaws ... IV - 4-4 Test Equipment ... IV - 4-5 Front Panel Performance Check ... IV - 4-6 Accuracy Check ... IV - 4-7 Adjustment after Tube Replacement ... IV - 4-8 Trouble Localization ... IV - 4-9 Adjustment after Current Probe Replacement ... IV - 4-10 Complete Adjustment Procedure ... IV - SECTION V REPLACEABLE PARTS Table of Replaceable Parts ... V - 1

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