Fluke 8842a instruction manual Theory of Operation

Chapter 5

Theory of Operation

	Title	Page
5-1.	INTRODUCTION	5-3
5-2. OVERALL FUNCTIONAL DESCRIPTION		5-3
5-3.	DETAILED CIRCUIT DESCRIPTION	5-4
5-4.	DC SCALING	5-4
5-5.	VDC Scaling	5-6
5-6.	VDC Protection	5-7
5-7.	mA DC Scaling	5-7
5-8.	Analog Filter	5-7
5-9.	TRACK/HOLD CIRCUIT	5-8
5-10.	Track Configuration	5-10
5-11.	Settling Configuration	5-11
5-12.	Hold Configuration	5-11
5-13.	Pre-Charge Configuration	5-11
5-14.	PRECISION VOLTAGE REFERENCE	5-11
5-15.	OHMS CURRENT SOURCE	5-12
5-16.	OHMS PROTECTION	5-13
5-17.	OHMS FUNCTIONS	5-13
5-18.	2-Wire Ohms	5-13
5-19.	4-Wire Ohms	5-15
5-20.	A/D CONVERTER	5-15
5-21.	Timing/Data Control	5-17
5-22.	Precision DAC	5-17
5-23.	A/D Amplifier	5-18
5-24.	Bootstrap Supplies	5-18
5-25.	DISPLAY	5-18
5-26.	KEYBOARD	5-19
5-27.	DIGITAL CONTROLLER	5-19
5-28.	In-Guard Microcomputer	5-21
5-29.	Function and Range Control	5-23
5-30.	A/D Control and Computation	5-23
5-31.	Calibration Correction	5-23
5-32.	Keyboard/Display Control	5-24
5-33.	Troubleshooting Modes	5-24
5-34.	Guard-Crossing Communication	5-24
5-35.	GUARD CROSSING	5-24

5-1