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RESISTANCE MEASUREMENTS

Figure 5 shows a simplified diagram of the resistance measurement function.

Figure 5  Simplified Resistance Measurement Diagram

External
Resistor

100

900

90k

900k

9M

9k

2k

200

20k

200k

2M

20M

Voltage

Source

Reference

Voltage

Low

Pass
Filter

7106R

DC

AC CAP

A simple series circuit is formed by the voltage
source, a reference resistor from the voltage divider
(selected by range switches), and the external
unknown resistor. The ratio of the two resistors is
equal to the ratio of their respective voltage drops.
Therefore, since the value of one resistor is known,
the value of the second can be determined by using
the voltage drop across the known resistor as a
reference. This determination is made directly by
the A/D converter.

Overall operation of the A/D converter during a
resistance measurement is basically as described
earlier in this section, with one exception.

The

reference voltage present during a voltage
measurement is replaced by the voltage drop
across the reference resistor.

This allows the

voltage across the unknown resistor to be read
during the read period. As before, the length of the
read period is a direct indication of the value of the
unknown.

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(D) Diode Test

1. Set the selector switch to the “Ohm” position.

2. Connect the red test lead to “V/

” input jack and

the black one to the “COM” jack.

3. Set the range selector knob to the “        ”

position.

4. If the semiconductor junction being measured is

connected to the circuit, turn off the power to the
circuit being tested and discharge all of the
capacitors.

5. Connect the test leads to the device and read

forward value on the digital display.

6. If the digital reads overrange (1), reverse the

lead connections.

The placement of the test leads when the
forward reading is displayed indicates the
orientation of the diode.

The red lead is positive and the black lead is
negative.

If overrange (1) is displayed with both lead
connections, the junction is open.

(E) Transistor  h

FE

Measurement

1. Set the selector switch to “DC”.

2. The transistor must be out of circuit. Set the

rotary/function switch to the h

FE

position.

3. Plug the emitter, base and collector leads of the

transistor into the correct holes in either the NPN
of the PNP transistor test socket, whichever is
appropriate for the transistor you are checking.

4. Read the h

FE

(beta or DC current gain) on the

display.

(F) Capacitance Measurement

1. Set the range selector knob to the “FARAD”

position.

2. Set the range selector knob to the desired

capacitance position.

3. Short the leads of the capacitor to be tested

together to insure that there is no charge on the
capacitor.

4. Insert the capacitor leads into the capacitor test

socket. Note that there are two groups of holes.
One lead must be inserted into one of group one,
and the other lead must be inserted into one of
the holes of group two.

5. Read the capacitance value on the digital

display.

Summary of Contents for M-2665K

Page 1: ...ttp www elenco com e mail elenco elenco com DIGITAL MULTIMETER KIT MODEL M 2665K WIDE RANGE DIGITAL MULTIMETER WITH CAPACITANCE AND TRANSISTOR TESTING FEATURES Assembly and Instruction Manual Elenco E...

Page 2: ...xperience 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 a...

Page 3: ...scharge as fixed rate slope When the charge is equal to the initial starting point autozero level the read period is ended Since the discharge slope is fixed during the read period the time required i...

Page 4: ...is CAUTION sign denotes a hazard It calls attention to a procedure practice or the like which if not correctly adhered to could result in damage to or destruction of part or all of the instrument This...

Page 5: ...ck 3 Set the range selector knob to the position 4 If the semiconductor junction being measured is connected to the circuit turn off the power to the circuit being tested and discharge all of the capa...

Page 6: ...leads to the device or circuit being measured 5 Turn on the power to the device or circuit being measured The voltage value will appear on the digital display along with the voltage polarity 6 Turn o...

Page 7: ...es 2 Avoid any excessive accumulation of resin build up whenever you solder a connection 3 Take your time assembling the circuit board Work at a slow pace Remember that accuracy is far more important...

Page 8: ...remove the solder and the iron and let the connection cool The solder should have flowed smoothly and not lump around the wire lead 4 Here is what a good solder connection looks like 2 Insufficient s...

Page 9: ...0 1 2 3 4 5 8 9 Multiply By 1 10 100 1k 10k 100k 01 0 1 Multiplier Note The letter R may be used at times to signify a decimal point as in 3R3 3 3 10 F 16V 103K 100V The letter M indicates a tolerance...

Page 10: ...crew 1 2 turn Slip the two shims under the knob see Figure L If they do not slip in turn back the screw another 1 4 turn Tighten the screw just enough so that the shims can be pulled out You should no...

Page 11: ...0000 1 PC Board 516000A 1 Solder Roll 551135 1 Battery Snap BAT 590098 1 Battery 590009 1 LCD Window Plate 621002A 1 Range Selector Knob 622003 1 Bushing 624004 Qty Description Part 1 LCD Stopper 6290...

Page 12: ...N5232 Diode see Figure C BAT Battery Snap Insert both wires through the hole and mount the red wire to the hole and the black wire to the hole Solder the wires from the top legend side Notch Notch 24...

Page 13: ...Range Selector Knob LCD Window Plate NOTE If the range selector switch becomes hard to turn then loosen the M2 3 x 8 screw slightly 23 Testing Procedure SECTION C AC voltage and current circuit Measu...

Page 14: ...R1 9M 5 1 2W white black black yellow green 179051 1 VR1 200 220 Potentiometer 191320 Note Some resistors may not have a color coding but they will have the value imprinted on them Note Resistor toler...

Page 15: ...es orange white red red brown see Figure E C1 22 F Lytic Capacitor see Figure F R27 2k 1 1 4W Res red blk blk brown brown see Figure E R28 1 3k 1 1 4W Res brn orange blk brn brn see Figure E R46 5 6k...

Page 16: ...of 1 10 amps If the tests are not working check for cold solder joints and part values Turn the meter off and remove the battery and test leads DO NOT PROCEED TO SECTION C WITHOUT YOUR INSTRUCTOR S AP...

Page 17: ...der the socket to the PC board Insert the IC into the socket with the notch as shown below Socket Notch C8 Figure I Mount the capacitor with the negative lead in the negative hole and the positive lea...

Page 18: ...own brown brown 141930 1 R40 4 12k 1 1 4W yellow brown red brown brown 144130 1 R9 9k 1 1 4W white black black brown brown 149030 1 R38 10k 1 1 4W brown black black red brown 151030 1 R43 11k 1 1 4W b...

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