1 TECHNICAL SPECIFICATION 1.1 Specification 2 GENERAL DESCRIPTION 2.1 Introduction 2.2 Measuring Head 2.3 Reduction of Display Jitter 2.4 Noise Cancellation 2.5 Measurement Principles 2.5 Storage of Front Panel Settings 2.7 GPIB Interface 2.8 Maintenance 3 PREPARATION FOR USE 3.1 Introduction 3.2 Power Supply 3.2.1 AC Voltage Range Setting 3.2.2. Line Fuse 3.2.3 DC Fuse 3.2.4 Power Lead 3.3 Connection of Measuring Heads 3.4 Fitting the Fixed Rack Mounting Kit 11-1496 3.5 Removal and Replacement of the Covers 3.6 Preparation for Use With the GPIB 3.6.1 Interface Connector 3.6.2 Address Setting 4 OPERATING INSTRUCTIONS 4.1 Introduction 4.2 Description of Controls, Indicators and Connectors 4.2.2 Front Panel Items 4.2.3 Rear Panel Items 4.3 Switching On 4.4 Measuring Head Calibration 4.4.1 The FACTORY ECAL 4.4.1.2 Using the CALIBRATOR Sockets 4.4.1.3 Using an External Calibration Source 4.4.2 The USER ECAL 4.4.2.3 Using the CALIBRATOR Sockets 4.4.2.4 Using an External Calibration Source 4.4.2.5 USER ECAL Factor Enablement 4.5 Measuring Head Attachments 4.5.1 50 fi Attenuators 4.5.2 Signal Amplifiers 4.5.3 High Impedance Probes 4.5.4 Low Impedance Probes

1 TECHNICAL SPECIFICATION 1-1 1.1 Specification 1-1 2 GENERAL DESCRIPTION 2-1 2.1 Introduction 2-1 2.2 Measuring Head 2-1 2.3 Reduction of Display Jitter 2-2 2.4 Noise Cancellation 2-2 2.5 Measurement Principles 2-2 2.6 Storage of Front Panel Settings 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 Connection of Measuring Heads 3-2 3.4 Fitting the Fixed Rack Mounting Kit 11-1496 3-3 3.5 Removal and Replacement of the Covers 3-4 3.6 Preparation for Use With the GPIB 3-4 3.6.1 Interface Connector 3-4 3.6.2 Address Setting 3-5 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 4-8 4.4 Measuring Head Calibration 4-8 4.4.1 The FACTORY ECAL 4-8 4.4.1.2 Using the CALIBRATOR Sockets 4-9 4.4.1.3 Using an External Calibration Source 4-9 4.4.2 The USER ECAL 4-10 4.4.2.3 Using the CALIBRATOR Sockets 4-10 4.4.2.4 Using an External Calibration Source 4-11 4.4.2.5 USER ECAL Factor Enablement 4-11 4.5 Measuring Head Attachments 4-11 4.5.1 50 Q Attenuators 4-11 4.5.2 Signal Amplifiers 4-12 4.5.3 High Impedance Probes 4-12 4.5.4 Low Impedance Probes 4-13 4.6 Display of ECAL Factors 4-13 4.7 Frequency Response 4-13 4.8 Setting of Averaging Time 4-14 4.9 Continuous Averaging Mode 4-15 4.10 Ranging Mode Setting 4-15 4.11 Voltage Primary Measurement Function 4-16 4.12 Power Primary Measurement Function 4-16 4.13 Ratio Measurements 4-17 4.14 Percentage Difference Measurements 4-18 4.15 Null Measurements 4-19 4.16 dB Measurements 4-19 4.17 Analogue Display 4-20 4.18 Storage of Front Panel Settings 4-20 4.19 Special Functions 4-21 4.20 Error Codes 4-21 4.21 Control Via the GPIB 4-24 4.22 Remote/Local Changeover 4-24 4.22.1 Local to Remote Changeover 4-24 4.22.2 Remote to Local Changeover 4-24 4.22.3 Local Lockout 4-25 4.23 Command Codes for Addressed Mode Operation 4-25 4.24 Entry of Numerical Values 4-34 4.25 Output Message Format 4-35 4.26 Status Byte Format 4-36 4.27 Service Request (SRQ) Output 4-36 4.28 Logic Levels 4-36 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 Sampling System 5-1 5.2.3 The Analogue Processing System 5-2 5.2.4 The Microprocessor System 5-2 5.2.4.3 Digital Signal Processing 5-3 5.2.4.4 Instrument Control 5-3 5.2.5 The Keyboard/Display System 5-3 5.2.6 The Calibrator System 5-4 5.2.7 The GPIB Interface 5-4 5.3 Technical Description 5-7 5.3.1 The Sampling System 5-7 5.3.1.2 10 Hz Triangular Waveform Generation 5-7 5.3.1.3 Voltage Controlled Oscillator 5-7 5.3.1.4 Sampling Pulse Generation 5-8 5.3.1.5 Sampling Bridge Operation 5-8 5.3.1.6 Pulse Amplification 5-8 5.3.1.7 Bias Control Circuit 5-9 5.3.2 Analogue Signal Processing System 5-9 5.3.2.2 Input Multiplexer 5-9 5.3.2.3 Switched Gain Amplifier 5-9 5.3.2.4 Second Sampler 5-10 5.3.2.5 True RMS Detector 5-12 5.3.2.6 Output Sample and Hold 5-16 5.3.2.7 Auto-Zeroing 5-16 5.3.2.8 Prevention of Lock Up 5-17 5.3.3 The Microprocessor System 5-17 5.3.3.4 Analogue to Digital Conversion 5-18 5.3.3.5 Digital Data Input 5-19 5.3.3.6 Digital Data Processing 5-19 5.3.3.7 Serial Data Ouptut to Display 5-19 5.3.3.8 Parallel Data Output to the GPIB Interface 5-19 5.3.3.9 Data Input from the GPIB Interface 5-19 5.3.3.10 Data Input from the Keyboard 5-20 5.3.3.11 Attenuator, Measuring Head and Calibrator Control 5-20 5.3.3.12 The Chip Select Circuit 5-21 5.3.3.13 Reset and Memory Supply Changeover Circuit 5-21 5.3.3.14 Test Switch Bank S30 5-22 5.3.4 The Keyboard/Display System 5-22 5.3.4.3 The Keyboard 5-22 5.3.4.4 The Liquid Crystal Display 5-22 5.3.4.5 The LED Indicators 5-23 5.3.5 The Calibrator System 5-23 5.3.5.2 The Internal Calibrator 5-23 5.3.5.3 The External Calibrator 5-24 5.3.6 The GPIB Interface 5-24 5.3.6.2 Address Setting and Recognition 5-24 5.3.6.3 Operation as a Listener 5-24 5.3.6.4 Operation as a Talker 5-25 5.3.6.5 Detection of the Serial Poll Disable Message 5-26 APPENDIX 1 Analysis of RMS Measuring Circuit 5-27 APPENDIX 2 Operation of Linearised Transconductance Multiplier 5-29 6 MAINTENANCE 6-1 6.1 Introduction 6-1 6.2 General Maintenance Information 6-1 6.2.1 Repair and Calibration of the Measuring Head 6-1 6.2.2 Battery Replacement 6-1 6.2.3 Special Functions for Maintenance Purposes 6-3 6.2.4 Test Switches 6-4 6.3 Fault Finding on Assemblies 19-1014 and 19-1017 6-4 6.3.1 Introduction 6-4 6.3.2 Assembly 19-1014 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 6-12 6.5.1 Introduction 6-12 6.5.2 Test Equipment Required 6-12 6.5.3 Temperature During Calibration 6-12 6.5.4 Signal Source Level Setting 6-12 6.5.5 Additional Measuring Head 6-12 6.5.6 Setting Up the Power Supplies 6-14 6.5.7 Setting Up Assembly 19-1014 6-18 6.5.8 Setting the Measuring Head Bias Balance 6-18 6.5.9 Setting the Second Sampler Pulse Width 6-19 6.5.10 Setting the Internal Calibrator 6-19 6.5.11 Setting the External Calibrator 6-20 6.5.12 Setting the Upper Range Attenuators 6-21 6.5.13 Final Attenuator Setting 6-22 6.5.14 Checking Measuring Head Gain 6-23 6.5.15 Noise Checks 6-23 6.5.16 Linearity Adjustment 6-24 6.5.17 Accuracy Check 6-25 6.5.18 Frequency Response 6-27 6.5.19 VSWR Check 6-29 6.5.20 Insertion Loss 6-30 6.6 Dismantling and Reassembly 6-31 6.6.1 Introduction 6-31 6.6.2 Removal and Replacement of the Covers 6-31 6.6.3 Removal of Assemblies 19-1015 and 19-1016 6-31 6.6.4 Removal of the Front Panel 6-32 6.6.5 Removal of Assembly 19-1013 6-33 6.6.6 Replacement of the LCD 6-33 6.6.7 Calibrator Sockets 6-35 7 PARTS LIST AND CIRCUIT DIAGRAMS Parts List: Front and Rear Panel Assemblies Parts List 1 Parts List: Measuring Head Assembly Parts List 3 Parts List: Keyboard and Display Assembly Parts List 7 Parts List: Processor Assembly Parts List 9 Parts List: Signal Converter Assembly Parts List 15 Parts List: Amplifier Assembly Parts List 19 Parts List: GPIB Assembly Parts List 27 Parts List: GPIB Connector Assembly Parts List 29 Internal Layout Fig. 1 Measuring Head Assembly: Component Layout Fig. 2 Circuit Diagram Fig. 3 Keyboard and Display Assembly: Component Layout Fig. 4 Circuit Diagram Fig. 5 Processor Assembly: Component Layout Fig. 6 Circuit Diagram Fig. 7 Signal Converter Assembly: Test Waveforms 7-1 Component Layout Fig. 8 Circuit Diagram Fig. 9 Amplifier Assembly: Test Waveforms 7-3 Component Layout Fig. 10 Circuit Diagram Fig. 11 GPIB Assembly: Component Layout Fig. 12 Circuit Diagram Fig. 13 GPIB Connector Assembly: Component Layout Fig. 14 Circuit Diagram Fig. 15 Interconnections Fig. 16