Fluke 12, 11, 10 Service Manual

®

10,11,12

Multimeters

Service

PN 900824

March 1992 Rev.1, 7/93

© 1992-1993 Fluke Corporation, All rights reserved. Printed in USA All product names are trademarks of their respective companies.

WARRANTY

Fluke warrants to the original product purchaser that each product it manufactures will be free from defects in material and workmanship under normal use and service. The warranty period is controlled by the warranty document furnished with each product and begins on the date of shipment. Fluke’s warranty does not apply to fuses, batteries, CRTs or any product which, in Fluke’s opinion, has been misused, altered, neglected, or damaged by accident or abnormal conditions of operation or handling.

To obtain warranty service in the USA, call 1-888-99-FLUKE (1-888-993-5853). Outside the USA, contact your nearest Fluke sales or service representative. Fluke assumes no risk for damage in transit. Fluke will, at its option, repair or replace the defective product free of charge or refund the purchase price. However, if Fluke determines that the failure was caused by misuse, alteration, accident, or abnormal condition of operation or handling, you will be billed for the repair and the repaired product will be returned to you transportation prepaid.

THIS WARRANTY IS EXCLUSIVE AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR USE. FLUKE WILL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR LOSS OF DATA, WHETHER IN CONTRACT, TORT, OR OTHERWISE.

Some states do not allow the exclusion or limitation of incidental or consequential damages, or implied warranty periods, so the above limitations may not apply to you. Other rights may vary from state to state.

Fluke Corporation	Fluke Europe B.V
P.O. Box 9090	P.O. Box 1186
Everett, WA 98206-9090	5602 BD Eindhoven
U.S.A.	The Netherlands

MULTIMETER SAFETY

The Fluke 10, 11, 12 Multimeters have been designed and tested according to IEC Publication 348, Safety Requirements for Electronic Measuring Apparatus. This manual contains information and warnings which must be followed to ensure safe operation and retain the meter in safe condition. Use of this equipment in a manner not specified herein may impair the protection provided by the equipment.

These mutimeters comply with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) these multimeters may not cause harmful interference, and

(2) these multimeters must accept any interference received, including interference that may cause undesired operation.

Some common international electrical symbols used in this manual are shown below.

	B	AC - ALTERNATING	Y	DANGEROUS
		CURRENT		VOLTAGE
	F	DC - DIRECT	J	EARTH GROUND
		CURRENT
	D	EITHER AC OR DC	W	SEE EXPLANATION
		CURRENT		IN MANUAL
	I	FUSE	T	DOUBLE INSULATION
				FOR PROTECTION
				AGAINST ELECTRIC
				SHOCK

Before using the meter, read the following safety information carefully. In this manual, "WARNING," is reserved for conditions and actions that pose hazard(s) to the user; "CAUTION," is reserved for conditions and actions that may damage your meter.

•Avoid working alone

•Follow all safety procedures for equipment being tested.

•Inspect the test leads for damaged insulation or exposed metal. Check test lead continuity. Damaged leads should be replaced.

•Be sure the meter is in good operating condition.

•Select the proper function for your measurement.

•To avoid electrical shock, use caution when working above 60V dc or 30V ac RMS.

•Disconnect the live test lead before disconnecting the common test lead.

• Disconnect the power and discharge high-voltage capacitors before testing in Ω and

LR.

•When making a current measurement, turn the circuit power off before connecting the meter in the circuit.

•Check meter fuses before measuring transformer secondary or motor winding current. An open fuse may allow high voltage build-up, which is potentially hazardous.

•Use clamp-on probes when measuring circuits exceeding 10 amps.

•When servicing the meter, use only the replacement parts specified.

•Do not allow meter to be used if it is damaged or if its safety is impaired.

Table of Contents

Chapter		Title	Page
1	Introduction and Specifications ........................................................		1-1
	1-1.	Introduction...........................................................................................	1-1
	1-2.	Specifications........................................................................................	1-1
2	Theory of Operation ...........................................................................		2-1
	2-1.	Introduction...........................................................................................	2-3
	2-2.	Theory of Operation..............................................................................	2-3
	2-3.	Analog Measurement IC (U1) ..........................................................	2-3
	2-4.	Microcomputer IC (U2)....................................................................	2-3
	2-5.	VCHEK Input Resistance.................................................................	2-3
3	Maintenance........................................................................................		3-1
	3-1.	Introduction...........................................................................................	3-3
	3-2.	Disassembly and Reassembly ...............................................................	3-3
	3-3.	Cleaning ................................................................................................	3-7
	3-4.	Performance Tests.................................................................................	3-7
	3-5.	Calibration ............................................................................................	3-8
4	Replaceable Parts and Schematics...................................................		4-1
	4-1.	Introduction...........................................................................................	4-3
	4-2.	How To Obtain Parts ............................................................................	4-3
	4-3.	Schematics ............................................................................................	4-3
	4-4.	Warranty and Service Centers ..............................................................	4-4

i

List of Tables

Table	Title	Page
1-1.	Specifications .........................................................................................................	1-2
2-1. Electrical Components on Main PCA ....................................................................		2-4
2-2.	U1 Pinout Table .....................................................................................................	2-5
3-1.	Required Equipment...............................................................................................	3-7
3-2. Performance Tests for Fluke 10 .............................................................................		3-9
3-3. Performance Tests for Fluke 11 and 12..................................................................		3-10
4-1.	Final Assembly.......................................................................................................	4-5
4-2.	A1 Main PCA.........................................................................................................	4-7

iii

List of Figures

Figure	Title	Page
2-1. Typical VCHEK Input Resistance with DC Volts Function Selected ...................		2-7
3-1.	Disassembled Unit..................................................................................................	3-4
3-2. Removing and Reinserting the Printed Circuit Assembly......................................		3-5
3-3.	Calibration Adjustment ..........................................................................................	3-10
4-1.	Final Assembly Drawing........................................................................................	4-6
4-2. A1 Main PCA Components....................................................................................		4-9
4-3.	Fluke 10 Schematic ................................................................................................	4-10
4-4.	Fluke 11 Schematic ................................................................................................	4-12
4-5.	Fluke 12 Schematic ................................................................................................	4-14

v

Chapter 1

Introduction and Specifications

	Title	Page
1-1.	Introduction...........................................................................................	1-3
1-2.	Specifications........................................................................................	1-3

1-1

Introduction and Specifications 1

Introduction

1-1. Introduction

WARNING

SERVICE PROCEDURES DESCRIBED HEREIN SHOULD BE

PERFORMED BY QUALIFIED PERSONNEL ONLY. TO AVOID

ELECTRIC SHOCK, PERFORM ONLY THOSE SERVICE

PROCEDURES IN THIS INSTRUCTION SHEET.

The 10 Series Service Manual provides the information necessary to service the Fluke Model 10, Model 11, and Model 12 Multimeters. The following information is provided in this publication:

•Specifications (Section 1)

•Basic theory of operation (Section 2)

•Disassembly and reassembly (Section 3)

•Performance tests (Section 3)

•Calibration (Section 3)

•Illustrated parts lists and schematic diagram (Section 4)

•Refer to the Users Manual for operating instructions.

1-2. Specifications

Specifications are in Table 1-1. Accuracy is specified for a period of one year after calibration, at 18° C to 28° C (64° F to 82° F) with relative humidity to 90%. AC conversions are ac-coupled, average responding, and calibrated to the rms value of a sine wave input.

Accuracy specifications are given as:

±([% of reading] + number of least significant digits])

1-3

10, 11, 12 Multimeters

Service Manual

					Table 1-1. Specifications
Maximum Voltage				600V ms
Between any Terminal
and Earth Ground
Display				3 3/4-digits, 4000 counts, updates 4/sec
Operating Temperature				-10° C to 50° C
Storage Temperature				-30° C to 60° C indefinitly (to -40° C for 100 hrs)
Temperature Coefficient				0.1 x (specified accuracy)/° C (<18° C or >28° C)
Relative Humidity				0% to 90% (-10° C to 35° C) 0% to 70% (35° C to 50° C)
Battery Type				9V, NEDA 1604 or IEC 6F22
Battery Life				650 continious hours with alkaline 450 continious hours with carbon-zinc
Shock, Vibration				1 meter shock. Per MIL-T-28800D for a Class 3 Instrument
Size (HxWxL)				1.35 in x 2.75 in x 5.55 in (3.46 cm x 7.05 cm x 14.23 cm)
Weight				10 oz (286 g)
Safety				Designed to Protection Class II requirement of UL1244, ANSI/ISA-S82,
				CSA C22.2 No 231, and VDE 0411, and IEC 1010 overvoltage category
				III.
EMI Regulations				Complies with FCC Part 15, Class B, and VDE 0871B.
Function		Range				Resolution		Accuracy (50 to 400 Hz)
								Model 10		Models 11/12
Volts AC		4000 mV*				1 mV		±(2.9%+3)		±(1.9%+3)
		4.000V				0.001V		±(2.9%+3)		±(1.9%+3)
		40.00V				0.01V		±(2.9%+3)		±(1.9%+3)
		400.0V				0.1V		±(2.9%+3)		±(1.9%+3)
		600V				1V		±(2.9%+3)		±(1.9%+3)
Volts DC		4000 mV				1 mV		±(1.5%+2)		±(0.9%+2)
		4.000V				0.001V		±(1.5%+2)		±(0.9%+2)
		40.00V				0.01V		±(1.5%+1)		±(0.9%+1)
		400.0V				0.1V		±(1.5%+1)		±(0.9%+1)
		600V				1V		±(1.5%+1)		±(0.9%+1)
Resistance		400.0Ω				0.1Ω		±(1.5%+2)		±(0.9%+2)
		4.000 kΩ				0.001 kΩ		±(1.5%+1)		±(0.9%+1)
		40.00 kΩ
						0.01 kΩ		±(1.5%+1)		±(0.9%+1)
		400.0 kΩ
						0.1 kΩ		±(1.5%+1)		±(0.9%+1)
		4.000 MΩ
						0.001 MΩ		±(1.5%+1)		±(0.9%+1)
		40.00 MΩ
						0.01 MΩ		±(1.9%+3)		±(1.5%+3)
Capacitance		1.000 µ	F			0.001 µ F		NA		±(1.9%+2)
		10.00 µ	F			0.01 µ F		NA		±(1.9%+2)
		100.0 µ
			F			0.1 µ F		NA		±(1.9%+2)
		1000 µ F
						1 µ F		NA		±(1.9%+2)
		10000 µ F
						10 µ F		NA		±(10%+90) Typical
Continuity/Diode		2.000V				0.001V		±(1.5%+2)		±(0.9%+2)
Test

*The 4000 mV range can only be entered in the manual range mode. Use the 4000 mV range with accessories.

** The beeper is guaranteed to come on at <25Ω and turn off at >250Ω . The meter detects opens or shorts of 250 µ s or longer.

1-4

Introduction and Specifications

1

Specifications

Table 1-1. Specifications (cont)

Function

Overload

Input Impedance

Common Mode

Normal Mode

Protection*

(Nominal)

Rejection Ratio

Rejection

(1 kΩ Unbalance)

Volts DC

600V rms

>10 MΩ <100 pF

>100 dB at dc, 50 Hz,

>50 dB at 50 Hz

kCHEK & LoZ = >2 kΩ

or 60 Hz

or 60 Hz

<200 pF**

Volts AC

600V rms

>5 MΩ <100 pF kCHEK

>60 db, dc to 60 Hz

& LoZ = >2 kΩ <200

pF** (ac-coupled)

Resistance

Open Circuit

Full Scale Voltage To

Short Circuit

Test Voltage

4.0 MΩ

40 MΩ

Current

600V rms

<1.5V dc

<450 mV

1.5V dc

<500 uA

dc

Diode

600V rms

2, 4-3. 0V dc

2,400V dc

0.95 mA typical

*3 x 106 V Hz Maximum

**Models 11 and 12 only

MIN MAX Recording with Elapsed Time (Model 12 Only)

Specified accuracy of the measurement function ± 12 digits for changes >200 ms in duration (±40 digits in ac). Typical 100 ms response to 80%.

Elapsed Time		Resolution		Accuracy
0 to 100 hours		1 minute		0.3% typical
(99:59)

Continuity Capture (Model 12 Only)

Detects opens or shorts of 250 µ s or longer.

1-5

Chapter 2

Theory of Operation

	Title	Page
2-1.	Introduction...........................................................................................	2-3
2-2.	Theory of Operation .............................................................................	2-3
2-3.	Analog Measurement IC (U1) ..........................................................	2-3
2-4.	Microcomputer IC (U2)....................................................................	2-3
2-5.	VCHEK Input Resistance.................................................................	2-3

2-1

10, 11, 12 Multimeters

Service Manual

2-2

Theory of Operation 2

Introduction

2-1. Introduction

Section 2 provides a basic theory of operation for the Series 10 Multimeters. Electrical components on the printed circuit assembly (A1 Main PCA) are listed in Table 2-1. Refer to Figure 4-2 for the location of these components and Figures 4-3 through 4-5 for the schematic diagrams.

2-2. Theory of Operation

The analog/digital IC (U1) implements the electrical measurement functions. See Table 2-2 for pin names and descriptions. The microcomputer (U2) controls U1, the LCD (U3), and the user interface. Discrete components support U1 and U2, provide reference standards for measurements, and provide input overload protection.

2-3. Analog Measurement IC (U1)

U1 implements the following analog functions: a/d converter, ac to dc converter, VCHEK circuitry (Models 11 and 12 only), active filter, passive filter, power supply, range configuration circuitry, signal routing circuitry, beeper driver, digital control circuitry, and digital U2 interface circuitry.

The a/d converter is a patented dual-rate, dual-slope converter. The dual-rate conversion allows for MIN MAX (Model 12 only) and fast autoranging functions. The ac to dc converter is full-wave rectified and average-responding. The active and passive filters are two-pole and one-pole low-pass filters (respectively) that are used for signal filtering prior to a/d conversion. The internal power supply generates a ground voltage nominally +3V relative to VSS. Range configuration circuitry connects the Z1 resistor network as needed for different ranges. Routing circuitry connects the various signal conditioning circuits as needed. The a/d converter and a counter are controlled by a state machine. Finally, digital circuitry interfaces with U2 via a parallel address and bidirectional data bus.

Voltage is measured using a ratio comparison of the unknown voltage to the reference voltage (REFI pin). Resistance is calculated using a ratio comparison of the voltage across the unknown resistor to the voltage across a precision reference resistor, with the same current in both. Capacitance is measured by determining the amount of charge added for a given dc voltage change.

2-4. Microcomputer IC (U2)

U2 writes range settings and a/d converter information to U1. U2 reads a/d converter results and status information. This includes the low battery check, slide-switch position, continuity check, and VCHEK data. The microcomputer performs math operations on the raw data from U1 and configures it for the LCD. U2 also reads pushbutton inputs. Finally, the 2.1 MHz clock signal at U2 is divided down to 131 kHz and sent to U1 (CLK pin) for the counter.

2-5. VCHEK Input Resistance

As shown in Figure 2-1, the input resistance for the VCHEK function is non-linear. The data in the graph are for the volts dc function (any range) and are the steady state values obtained after the PTC thermister (RT1) has stabilized. The data also apply for the volts ac function.

2-3

10, 11, 12 Multimeters

Service Manual

Table 2-1. Electrical Components on Main PCA

Circuit and Function

Analog Measurement IC

Microcomputer IC

Input Divider and Ohms Reference Resistor Network

Input Divider AC Coupling Capacitor

J2 Input Receptable Voltage Sense Resistor

J1 Input Receptable Voltage Sense Resistor

Reference Voltage for Volts Measurements

A/D Converter Integrate Capacitor

A/D Converter Autozero Capacitor

A/D Converter Gain Resistors

Active Filter Components

Passive Filter Components

AC to DC Converter Gain Resistors

AC to DC Converter AC Coupling Capacitor

Bias Current Setting Resistor

DGND-VSS Voltage Setting Resistors

Power Supply Bypass Capacitors

Reverse Battery Protection

System Clock

VCHEK Input Current Limiters

VCHEK input Positive Temp. Coef. Thermistor

VCHEK Input Voltage Clamp Circuit

VCHEK Input Fusible Resistor

Microcomputer Reset Circuit

On/Off and VCHEK Select Slide Switch

Beeper

Beeper Current Limiter

Slide Switch Protection

Switch Sense Bypass Capacitor

Input Divider Bypass Capacitor

Zero Ohm Jumpers

Component Designator(s)

U1

U2

Z1

C14

R17

R14

VR1, R4, R5, R6, R26

C2

C1

R1, R3, R15

R7, R8, C5, C6

R9, C7

R11, R12, R13

C8

R2

R10, R24

C3, C15

CR1

Y1

R16, R18, R29

RT1

Q1, Q2, CR2, R28

R19

R23, R25, C10, C13, CR3

S1

LS1

R22

E1

C9

C16

R20, R21, R27

2-4