Racal 5002 Level Meter
2.1 INTRODUCTION 2.1.1 The Racal-Dana Wideband Level Meter Model 5002 is a light, portable, but extremely versatile, microprocessor controlled instrument. It permits measurements to be made with exceptional accuracy on waveforms having high crest factors. Special automatic zeroing and noise cancelling circuits permit measurements to be made over a range of signal amplitudes extending from 316 V r.m.s. down to 30 uV r.m.s. The instrument has an auto ranging facility, but provision is made for manual range selection. 2.1.2 Measurements may be made on DC signals, on AC signals in the frequency range from 5 Hz to 20 MHz and on signals having both DC and AC components. A low pass filter can be switched in to restrict the operating bandwidth to 200 kHz (~3dB). 2.1.3 The instrument measures true r.m.s., mean, positive peak or negative peak voltages of the applied signal. Operator set values of resistance, voltage and power may be stored in the instrument, and, in addition to display of the measured value in voltage units, displays of the following computed values can be obtained: (a) Average or peak power, computed from V^/R. (b) The ratio of the computed power to the stored power level. (c) The ratio of the measured voltage to the stored voltage level. (d) The difference between the measured and stored voltage levels. (e) The difference between the computed and stored power levels. (f) The difference as in (d) expressed as a percentage of the stored voltage level. (g) The difference as in (e) expressed as a percentage of the stored power level. The instrument will also compute, and display, mean value scaled to r.m.s., peak·-to-peak value, form factor and crest factor. 2.1.4 The input common line is isolated from chassis earth by back-to-back diodes, which permit a voltage difference of ±0.5 V. The common line can be connected to chassis earth, if required, by means of an isolation override switch. 2.1.5 The instrument features a large, four digit, liquid crystal display (LCD). Coarse and fine LCD bar and dot displays form part of the display, and provide a pseudo-analogue form of indication. Units annunciators, GPIB status indicators and instrument status indicators are also incorporated. 2.2 CREST FACTOR 2.2.1 The maximum permitted crest factor on any range increases in inverse proportion to the displayed measurement. Errors will arise if the measured waveform has a significant proportion of its energy in harmonics which lie outside the instrument's measurement bandwidth. 2.3 OPERATING PRINCIPLES 2.3.1 Following a common input attenuator the instrument has separate AC and DC measurement channels. The AC channel features separate detectors for r.m.s., mean, positive peak and negative peak measurements, so that these waveform parameters are all measured simultaneously. 2.3.2 The detector outputs are connected in turn to an analogue to digital Converter. The microprocessor scans the Converter output every 0.1 second, reading each detector output in turn, One detector output, determined by the measurement function selected, is either converted directly to a display drive signal or processed, together with the contents of various internal stores, to provide power, difference or percentage difference display signals. 2.4 REDUCTION OF DISPLAY JITTER 2.4.1 The instrument has a variable averaging time, which may be set by the operator to ensure minimum jitter of the measurement indication when measurements are made on waveforms of high crest factor. The period over which measurements are averaged may be varied in steps of 0.1 second between 0.1 second and 99.9 seconds (nominal). 2.4.2 The display updating rate is set by the averaging time in use. To avoid the necessity for unacceptably low updating rates, continuous averaging of the measurements can be introduced by means of a special function. In this mode the display is updated every 0.1 second, the new displayed value being formed by adding Ν3ί of the current displayed value to (100-N%) of the new measurement. The effect of this is similar to filtering successive measurements in a single pole RC filter. The value of N is related to the time constant of the effective filter, which can be set by the operator, 2.5 STORAGE OF FRONT PANEL SETTINGS 2.5.1 Provision is made for the storage of up to twelve complete sets of front panel control settings, including the values set in the computed function stores, in a non-volatile memory. Each setting is allocated a number, and is retrieved and set by recalling that number. The front panel control settings in use when the instrument is switched off are automatically stored, and may be recalled when the instrument is switched on again. 2.6 CALIBRATION TO AN EXTERNAL SOURCE 2.6.1 The instrument display may be set to a reference value, when measurements are made on a reference signal source, by means of an operator selected calibration factor. The calibration factor, which is a divisor, is stored in the instrument, and may be enabled and disabled as required when making measurements on other signal sources. 2.7 GPIB Interface 2.7.1 An internally mounted Interface board permits the instrument to be controlled from, and communicate with, the IEEE 488 GPIB. The instrument may be used in the addressed mode or in the talk only mode. An adaptor to permit use with the I EC 625-1 GPIB is also available. 2.8 MAINTENANCE 2.8.1 It is recommended that customers should take advantage of the servicing and calibration service offered by Racal-Dana Instruments Ltd., and their agents. For customers wishing to carry out their own servicing, a comprehensive Maintenance Manual is available from Racal-Dana Instruments Ltd. When ordering a manual, the serial number of the instrument for which the manual is required should be quoted.

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Manual de serviço
Tipo de manual:
Manual de serviço
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ΤΗ 4026
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25 Outubro 2015
1 TECHNICAL SPECIFICATION 1-1 1.1 Specification 1-1 2 GENERAL DESCRIPTION 2-1 2.1 Introduction 2-1 2.2 Crest Factor 2-2 2.3 Operating Principles 2-2 2.4 Reduction of Display Jitter 2-2 2.5 Storage of Front Panel Settings 2-2 2.6 Calibration to an External Source 2-3 2.7 GPIB Interface 2-3 2.8 Maintenance 2-3 3 PREPARATION FOR USE 3-1 3.1 Introduction 3-1 3.2 Power Supply 3-1 3.2.1 AC Voltage Range Setting 3-1 3.2.2. Line Fuse 3-1 3.2.3 DC Fuse 3-2 3.2.4 Power Lead 3-2 3.3 Fitting the Fixed Rack Mounting Kit 11-1496 3-2 3.4 Removal and Replacement of the Covers 3-3 3.5 Preparation for Use with the GPIB 3-4 3.5.1 Interface Connector 3-4 3.5.2 Address Setting 3-4 4 OPERATING INSTRUCTIONS 4-1 4.1 Introduction 4-1 4.2 Description of Controls, Indicators and Connectors 4-1 4.2.2 Front Panel Items 4-1 4.2.3 Rear Panel Items 4-5 4.3 Switching On 4-6 4.4 Input isolation 4-6 4.5 Setting of Averaging Time 4-6 4.6 Continuous Averaging Mode 4-8 4.7 Input Filter 4-8 4.8 Ranging Mode Setting 4-9 4.9 Voltage Primary Measurement Function 4-9 4.10 Power Primary Measurement Function 4-9 4.11 Secondary Measurement Function Selection 4-10 4.12 Computed Functions 4-12 4.13 Ratio Measurements 4-12 4114 Percentage Difference Measurements 4-13 4.15 Null Measurements 4-14 4.16 dB Measurements 4-14 4.17 Analogue Display 4-15 4.18 Calibration to an External Signal 4-15 4.19 Storage of Front Panel Settings 4-16 4.20 Special Functions 4-17 4.21 Error Codes 4-19 4.22 Control via the GPIB 4-21 4.23 Remote/Local Changeover 4-21 4.23.1 Local to Remote Control Changeover 4-21 4.23.2 Remote to Local Control Changeover 4-22 4.23.3 Local Lockout (LLO) 4-22 4.24 Command Codes for Addressed Mode Operation 4-22 4.25 Entry of Numerical Values 4-31 4.26 Output Message Format 4-32 4.27 Status Byte Format 4-33 4.28 Service Request (SRQ) Output 4-33 4.29 Logic Levels 4-33 5 PRINCIPLES OF OPERATION 5-1 5.1 Introduction 5-1 5.2 Principles of Operation 5-1 5.2.1 Functional Systems 5-1 5.2.2 The Analogue Signal Processing System 5-1 5.2.3 The Microprocessor System 5-3 Digital Signal Processing 5-3 Instrument Control 5-3 5.2.4 The Keyboard/Display System 5-3 5.2.5 The GPIB Interface 5-4 5.3 Technical Description 5-7 5.3.1 Analogue Signal Processing System 5-7 Input Circuit 5-7 Input Coupling Selection 5-7 First Attenuator 5-7 Auto-Zero Switch 5-8 The Gain Controlled Amplifiers 5-8 The DC Detector 5-11 The RMS Detector 5-11 RMS Detector Sample and Hold 5-15 RMS Detector Auto-Zeroing 5-15 The Prevention of Lock up 5-16 The Peak Detectors 5-16 Peak Detector Auto Zeroing 5-17 The Mean Detector 5-18 DC/MEAN Detector Output Selection 5-21 5.3.2 The Microprocessor System 5-21 Detector Output Selection 5-22 Analogue to Digital Conversion 5-22 Digital Data Input 5-22 DC Polarity Input 5-22 Digital Data Processing 5-22 Serial Data Output to the Display 5-22 Parallel Data Output to the GPIB Interface 5-23 Data Input from the GPIB Interface 5-23 Data Input from the Keyboard 5-23 Control Line Logic Level Setting 5-24 The Chip Select Circuit 5-24 Reset and Memory Supply Changeover Circuit 5-25 Test Switchbank S30 5-25 5.3.3 The Keyboard/Display System 5-25 The Keyboard 5-26 The Liquid Crystal Display 5-26 The LED Indicators 5-26 5.3.4 The GPIB Interface 5-26 Address Setting and Recognition 5-27 Operation as a Listener 5-27 Operation as a Talker 5-27 Detection of the Serial Poll Disable Message 5-28 APPENDIX 1 Analysis of RMS Measuring Circuit 5-29 APPENDIX 2 Operation of Linearised Transconductance Multiplier 5-31 6 MAINTENANCE 6-1 6.1 Introduction 6-1 6.2 General Maintenance Information 6-1 6.2.1 Battery Replacement 6-1 6.2.2 Special Functions for Maintenance Purposes 6-2 6.2.3 Test Switches 6-3 6.3 Fault Finding on Assemblies 19-1024 and 19-1017 6-4 6.3.1 Introduction 6-4 6.3.2 Assembly 19-1024 6-4 6.3.3 Assembly 19-1017 6-4 6.4 Signature Analysis 6-8 6.4.1 Preparation for Signature Analysis 6-8 6.4.2 Connection of the Signature Analyser 6-8 6.4.3 Analysis Procedure 6-8 6.5 Calibration Procedure 6-11 6.5.1 Introduction 6-11 6.5.2 Test Equipment Required 6-11 6.5.3 Temperature During Calibration 6-11 6.5.4 Signal Source Level Setting 6-11 6.5.5 Isolation Test 6-11 6.5.6 Setting-Up the Power Supplies 6-13 6.5.7 Setting-Up Assembly 19-1024 6-15 6.5.8 Range Attenuator Setting 6-16 6.5.9 RMS Detector Setting 6-18 6.5.10 DC Channel Setting 6-19 6.5.11 Mean Detector Setting 6-20 6.5.12 Peak Detector Setting 6-22 6.5.13 Attenuator Check 6-23 6.5.14 RMS Detector Check 6-25 6.5.15 Mean and Peak Detectors Check 6-28 6.5.16 DC Channel Attenuator Check 6-30 6.5.17 Rectified Mean Check 6-31 6.5.18 35 MHz Frequency Response Check 6-32 6.6 Dismantling and Reassembly 6-33 6.6.1 Introduction 6-33 6.6.2 Removal and Replacement of the Covers 6-34 6.6.3 Removal of Assemblies 19-1021 and 19-1022 6-34 6.6.4 Removal of the Front Panel 6-35 6.6.5 Removal of Assembly 19-1023 6-35 6.6.6 Replacement of the LCD 6-36 7 Title Page PARTS LIST AND CIRCUIT DIAGRAMS Parts List; Front and Rear Panel Assemblies Parts List 1 Parts List: Keyboard and Display Assembly 19-1023 Parts List 3 Parts List: GPIB Assembly 19-1017 Parts List 5 Parts List: GPIB Connector Assembly 19-1018 Parts List 7 Parts List: Amplifier Assembly 19-1021 Parts List 9 Parts List: Detector Assembly 19-1022 Parts List 15 Parts List: Processor Assembly 19-1024 Parts List 23 Internal Layout Fig. 1 Keyboard and Display Assembly: Component Layout Fig. 2 Circuit Diagram Fig. 3 GPIB Assembly: Component Layout Fig. 4 Circuit Diagram Fig. 5 GPIB Connector Assembly: Component Layout Fig. 6 Circuit Diagram Fig. 7 Amplifier Assembly: Test Waveforms 7-1 Component Layout Fig. 8 Circuit Diagram Fig. 9 Detector Assembly: Test Waveforms 7-3 Component Layout F1g. 10 Circuit Diagram Fig. 11 Processor Assembly: Component Layout Fig. 12 Circuit Diagram Fig. 13 Interconnections Fig. 14

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