DIGITAL MULTIMETER KIT MODEL M-2665K WIDE RANGE DIGITAL MULTIMETER WITH CAPACITANCE AND TRANSISTOR TESTING FEATURES Elenco™ Electronics, Inc. 150 W. Carpenter Avenue Wheeling, IL 60090 (847) 541-3800 http://www.elenco.com e-mail: elenco@elenco.com Assembly and Instruction Manual Elenco™ Electronics, Inc. Copyright © 1991 Elenco™ Electronics, Inc.
INTRODUCTION QUIZ Assembly of your M-2665K Digital Multimeter Kit will prove to be an exciting project and give much satisfaction and personal achievement. If you have experience in soldering and wiring technique, you should have no problems. For the beginner, care must be given to identifying the proper components and in good soldering habits. Above all, take your time and follow the easy step-by-step instructions. Remember, “An ounce of prevention is worth a pound of cure”.
SCHEMATIC DIAGRAM A/D CONVERTER A simplified circuit diagram of the analog portion of the A/D converter is shown in Figure 2. Each of the switches shown represent analog gates which are operated by the digital section of the A/D converter. Basic timing for switch operation is keyed by an external oscillator. The conversion process is continuously repeated. A complete cycle is shown in Figure 2. converter can be divided into three consecutive time periods: autozero (AZ), integrate (INTEG) and read.
. OPERATION MAINTENANCE VOLTAGE MEASUREMENT Figure 3 shows a simplified diagram of the voltage measurement function. The input divider resistors add up 10MΩ with each step being a division of 10. The divider output should be withing –0.199 to +0.199V or the overload indicator will function. If the AC function is selected, the divider output is AC coupled to a full wave rectifier and the DC output is calibrated to equal the rms level of the AC input.
(D) Diode Test (F) Capacitance Measurement 1. Set the selector switch to the “Ohm” position. 1. Set the range selector knob to the “FARAD” position. 2. Connect the red test lead to “V/Ω” input jack and the black one to the “COM” jack. 3. Set the range selector knob to the “ position. RESISTANCE MEASUREMENTS Figure 5 shows a simplified diagram of the resistance measurement function. 2. Set the range selector knob to the desired capacitance position. ” DCΩ Low Pass Filter 100 3.
a a f a b b f g c e b g c e d 3-3 Method of Measurement a f b g d c e d BACKPLANE (A) DC/AC Voltage Measurement (C) Resistance Measurement 1. Set the selector switch to “DC” or “AC”. 1. Set the selector switch to the “Ohm” position. 2. Connect the red test lead to “V/Ω” input jack and the black one to the “COM” jack. 2. Connect red test lead to the “V/Ω” input jack and the black one to “COM”. 3. Set the range selector knob to the desired volt position.
Transistor hFE ASSEMBLY Range NPN PNP The meter kit has been divided into a number of sections to make the assembly easy and avoid major problems with the meter operation. Test Condition 10mA 2.8V 10mA 2.8V Diode Test IMPORTANT CONSTRUCTION NOTES 1. Wash your hands with soap and water before you assemble this kit. The high impedance areas on the circuit board can be contaminated by salt and oil from your skin.
CONSTRUCTION AC Voltage Introduction The most important factor in assembling your M-2665K Digital Multimeter Kit is good soldering techniques. Using the proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is recommended. The tip of the iron must be kept clean at all times and well tinned. Safety Procedures • Wear eye protection when soldering. • Locate soldering iron in an area where you do not have to go around it or reach over it.
1. FEATURES • Wide measuring ranges: IDENTIFYING CAPACITOR VALUES 34 ranges for AC/DC Voltage and Current, Resistance, Capacitance, TR hFE, Diode Test. • 10MΩ Input Impedance Capacitors will be identified by their capacitance value in pF (picofarads), nF (nanofarads), or µF (microfarads). Most capacitors will have their actual value printed on them. Some capacitors may have their value printed in the following manner. The maximum operating voltage may also be printed on the capacitor.
RESISTOR READING EXERCISE REINSTALLATION OF THE RANGE SELECTOR KNOB Before starting assembly of your digital multimeter project, you should be thoroughly familiar with the 5 band color code system. Many of the resistor values will be identified by color bands and it is easy to mistake their value if you read the colors incorrectly or read the value from the wrong end. Do the following exercise in resistor values. Place your answer in the box beneath the resistor. Answers are on the bottom of this page.
Amps Section hFE Section 1. 200mA scale not working: 1. Check for shorts on socket pins. A. Check fuse. 2. Measure across B terminal to COM terminal for 251kΩ. B. Measure across (A) terminal and (COM) terminal for 1Ω (set meter in 200mA). A. Lower or higher than 251kΩ; Check R14 and R15. 1. Lower or higher than 1Ω, Check R13. 2. 20mA scale not working: SECTION A Meter Display Circuit PARTS LIST - SECTION A If any parts are missing or damaged, see instructor or bookstore.
ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD TROUBLESHOOTING GUIDE In all of the following steps the components must be installed on the top legend side of the PC board. The board is turned to solder the component leads on the selector switch side. If the meter is not working, perform the U1 (7106R) Voltage Test first. This test is to verify that the IC and Reference Voltage are operational. Then perform the tests that pertain to the Function that is not working on your meter.
Testing Procedure SECTION C - AC voltage and current circuit Testing Procedure SECTION F Measure an AC voltage with a known accurate meter. Now measure the voltage with the kit meter. The meters should be the same voltage. Connect the kit meter and another meter of known accuracy in series. Set the meters in the 200mA position. Construct a circuit for an AC current and measure the circuit current. Both meters should have close to the same readings. If the meters do not agree, check the parts just added.
SECTION B DC Voltage & Current Circuit (A) Top Plates PARTS LIST - SECTION B RESISTORS Qty. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Symbol R13 R12 R6 R5 R28 R27 R46 R26 R4 R25 R3 R2 R1 VR1 Description 1Ω .5% 1/2W 9Ω .5% 1/4W 100Ω .5% 1/4W 900Ω .5% 1/4W 1.3kΩ 1% 1/4W 2kΩ 1% 1/4W 5.6kΩ 5% 1/4W 8.2kΩ 5% 1/4W 9kΩ .5% 1/4W 39.2kΩ 1% 1/4W 90kΩ .5% 1/4W 900kΩ .5% 1/4W 9MΩ .
FINAL ASSEMBLY ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD Peel off the protective backing on the top plates (A) and (B) and stick them to the top case. Peel off the protective backing on the battery cushion and stick it onto the bottom case. (These may be installed on the case already). top of the springs and then place a ball bearing on each spring. Press the top case onto the PC board. Using both hands, slide your fingers under the paper.
Push the four input sockets into the PC board holes from the selector switch side until they stop (see Figure G). Turn the board over as shown in Figure Ga and solder the sockets in place from the top legend side. Apply enough heat to allow the solder to flow around the input sockets (see Figure Gb). Push on the slide switch knob. Mount the two 9-pin component sockets to the PC board with the notch at the base of the socket in the direction shown in Figure I.
ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD SECTION C In all of the following steps the components must be installed on the top legend side of the PC board. The board is turned to solder the component leads on the selector switch side. AC Voltage & Current Circuit PARTS LIST - SECTION C D11 - 1N4148 Diode (see Figure C) R7 - 98.8Ω 1% 1/4W Res. (wht-gray-gray-gold-brn) (see Figure E) R8 - 900Ω 1% 1/4W Res. (wht-blk-blk-blk-brn) (see Figure E) R9 - 9kΩ 1% 1/4W Res.
SECTION D SECTION E Resistance Circuit Capacitance and Transistor Testing Circuit PARTS LIST - SECTION D Qty 1 Symbol PTC PARTS LIST - SECTION E Description 1kΩ Thermister Part # 190415 ASSEMBLE THE FOLLOWING COMPONENT TO THE PC BOARD The other components for this section have been installed already. PTC - Thermister 1kΩ Mount part in holes shown only RESISTORS Qty. 1 1 1 1 1 1 1 1 2 1 1 1 2 1 1 Symbol R7 R37 R8 R41 R40 R9 R38 R43 R39, R42 R44 R10 R45 R14, R15 Description 98.
