Range Doubler Multitester (220-0215) Operation Faxback Doc. # 6540 METER READING Keep the tester on a flat, non-metallic surface for the most accurate readings. Select a setting that gives a reading in the upper 1/3 or 1/2 of the meter scale. When you read the scale, look at it from the point where the pointer and its reflection in the mirror come together. Read from the scale that matches the - green for OHMS, red for ACV, and color of the function you select black for DCV/DCA and decibels. To read the AC/DC scale, use the appropriate markings based on the selected range. Marking Selected Range 0 to 250 0.25, 2.5, 25, 250 0 to 125 0.125, 1.25, 125 0 to 50 5, 50, 500 0 to 10 10, 1000 ZERO ADJUSTMENT If the pointer does not normally rest exactly over the zero at the left side of the AC/DC scale, adjust the plastic screw in the center of the tester face to bring the pointer to zero. OHMS ADJUSTMENT When measuring resistance on each OHMS range, you must bring the pointer to 0 at the right side of the upper green OHMS scale. To do this, connect the black test lead to the -COM jack and the red test lead to the +V-Ohms-A jack. Set the range switch to one of the OHMS positions. Then touch the test lead tips together, and adjust OHMS ADJ to bring the pointer to 0 on the right side of the OHMS scale. Notes: You must do this adjustment whenever you change the OHMS range. If you cannot adjust the pointer to 0 on the OHMS scale when the range switch is set to the x1, x10, or the x1K position, replace the 1.5V AA battery. If you cannot adjust the pointer to 0 on the OHMS scale when the range switch is set to the x10K position, replace the 9V battery. RANGE DOUBLER SWITCH If the reading is in the lower half of the scale when you measure ACV, DCV, DCA, or dB, set the range doubler switch to the V/2.A/2 setting, divide the range switch setting by two and read the appropriate scale. Examples: The range switch is set to 250 AC V and the range doubler switch is set to V/2.A/2: The range is 125 volts (250 divided by 2) and you should read the red scale, following the 0 to 125 markings. The range switch is set to 10A and the range doubler switch is set to the V/2.A/2 (the black test lead is connected to the -COM jack and the red test lead to the + 10A DC jack). The range is 5A 10 divided by 2), and you should read the black scale, following the 0 to 50 markings. USING THE TEST LEADS Use only the same type of test leads supplied with your tester. These test leads are rated for 1200 volts. Replacement test leads (Cat. No. 278-704) are available at your local Radio Shack store. Caution: Although these test leads are rated for 1200 volts, the maximum rating of the tester is 1000 VAC/DC. Do not attempt to measure any voltage greater than 1000 VAC/DC. Always observe correct test lead polarity when making DC measurements. The black lead should always be connected to the -COM jack. If you connect using the wrong polarity, the tester's pointer swings to the left and goes out of range. Connect the red lead to the +V-Ohm-A jack for making DC voltage measurements up to 250 V, DC current up to 500 mA, all AC voltages (up to 1000 VAC), and all resistance measurements. Connect the red lead to the +1000V DC jack when measuring DC voltages from 250-1000 V. Connect the red lead to the +10A DC jack when measuring DC current from 500 mA to 10 A. Warning: Never allow your fingers to touch the bare metal portion of the test leads (or circuit points) during measurements. Caution: Always disconnect the test leads when you have finished using the tester. DC VOLTAGE MEASUREMENTS Warning: Use extreme care when making high-voltage measurements. Do not touch the terminal or test lead tips. 1. Plug the black test lead into the -COM jack. 2. Plug the red test lead into the +V-Ohm-A jack if the voltage to be measured is under 250V. For voltages between 250-1000V, plug the red test lead into the +1000V DC jack. If you do not know the voltage level, plug the red test lead into the +1000V DC jack and start with the 250/1000V range. If the meter reading is in the lower half of the scale, plug the red test lead into the V-Ohms-A jack and lower the range using the range and range doubler switches until the reading is in the upper 1/2 or 1/3 of the scale. Note: Use the +1000V DC jack only with DC voltages of 250 to 1000V. 3. Set the range switch to one of the DCV positions. Caution: When excess voltage is applied to the 0.25 DCV or 0.125 DCV range, the fuse in the tester will blow, and the tester does not work until you replace the fuse. 4. Connect the test lead tips to the circuit to be tested, with the red lead to the positive supply and the black lead to the negative supply. 5. Set the range and the range doubler switches to get a meter reading in the upper 1/2 or 1/3 of the scale. 6. Read the voltage on the black DC scale. If the range doubler switch is set to V/2.A/2, divide the range switch setting by two and read the appropriate scale. AC VOLTAGE MEASUREMENTS Warning: Use extreme care when making high-voltage measurements. Do not touch the terminal or test lead tips. 1. Plug the black test lead into the -COM jack and the red lead into the +V-Ohm-A jack. 2. Set the range switch to one of the ACV positions. If you are uncertain about the level of the voltage to be measured, it is best to start at the highest range (1000V) and work down the scale. 3. Connect the test lead tips to the circuit to be tested. 4. Set the range and the range doubler switches as required to get a meter reading in the upper 1/2 or 1/3 of the scale. 5. Read the voltage on the red AC scale, following the black numbers printed below the red scale. If the range doubler switch is set to the V/2.A/2 position, divide the range switch setting by two and read the appropriate scale. HIGH-VOLTAGE MEASUREMENTS When you use the tester to probe for a voltage in a high-voltage circuit, we recommend that you do not try to position both of the test leads at once. Instead, clamp one lead to the neutral or ground lead of the circuit, using Radio Shack insulated slip-on alligator clips (Cat. No. 270-354). Then probe for voltages with the other probe and put your free hand in your pocket. This helps prevent you from accidentally touching a hot wire, since you need only concentrate on one test lead. Warning: Never clamp to a hot wire. If you do and then touch the other probe connected to the tester, you could receive an electric shock. AC VOLTAGE RIDING ON A DC SOURCE BIAS MEASUREMENTS When measuring an AC voltage superimposed on a DC voltage source bias, you cannot make ordinary measurements. In this situation, if you know the approximate voltage of the device to be measured and the voltage is under 30 V AC on a DC source bias, you can measure the voltage by connecting a 0.1 microf/100 V polyester film capacitor in series with the positive terminal of the voltage source and the red test lead. Set the range switch to either the 10 or 50 ACV position. Warning: Do not make this type of measurement if the AC voltage is greater than 100V with respect to each ground. MEASURING 3-PHASE AC VOLTAGES We designed your meter to measure household AC voltage. It is not intended for commercial or industrial use. Please note the following regarding 3-phase AC voltages. Warnings: Because of the dangers inherent in measuring 3-phase circuits, do not use this meter for such applications. The actual voltage can be greater than the circuit's rated line-to-ground voltage. To determine the line-to-line voltage, multiply the rated line- to-ground voltage by 1.732 (the square root of 3). For example, if the rated line-to-ground voltage is 640 volts, the line-to-line voltage is 640 x 1.732 = 1108 Volts. This voltage exceeds the meter's rating and you should not connect the meter to this circuit. RESISTANCE MEASUREMENTS Warning: Do not apply voltage to the test leads when the range switch is in an OHMS position. Doing so causes the fuse to blow, and the tester stops working. Before taking any resistance measurements, disconnect power to the unit under test and discharge any capacitors. It is best to remove any batteries from the unit under test and unplug any line cords. To make resistance measurements: 1. Plug the black test lead into the -COM jack and the red test lead into the +V-Ohms-A jack. 2. Leave the range doubler switch in the V-Ohms-A position. 3. Set the range switch to one of the OHMS positions. 4. Touch the test lead tips together and adjust OHMS ADJ to bring the pointer to 0 at the right side of the green OHMS scale. Note: You must adjust the pointer to 0 each time you change ranges in the OHMS function (except the CONT position). If you cannot adjust the pointer to 0, replace the battery. 5. Connect the test lead tips across the circuit or part under test. Note: When measuring a part's resistance, disconnect one side of the component under test so the remainder of the circuit does not interfere with the readings. 6. Read the resistance on the green OHMS scale. 7. Use the appropriate multiplier to find the correct resistance value. Multiply the value that the pointer indicates in the scale by 1, 10, 1000, or 10,000 depending on the range switch's position. When trying to identify the cathode and anode ends or the type of transistor (PNP or NPN), the actual polarity of the tester's voltage is the opposite of the test lead colors. The red test lead is the negative source and the black test lead is positive. CONTINUITY CHECK Follow these steps to check for continuity in a wire or circuit. 1. Plug the black test lead into the -COM jack and the red test lead into the +V-Ohms-A jack. 2. Set the range switch to CONT on the OHMS range. 3. Touch the test lead tips together to check the built-in-buzzer. If the buzzer does not sound, replace the 9V battery. 4. Connect the test leads to the unit under test. If the resistance is between 0 and 300 Ohms, the built-in-buzzer sounds. Note: The buzzer's sound level decreases as the resistance increases. DC CURRENT MEASUREMENTS To measure current, you must break the circuit and connect the test leads in series with the circuit. Warning: Do not apply voltage to the test leads when the range switch is set to a DCA position. Doing so blows the fuse, and the meter stops working. Note: The 10A range is not fuse protected. 1. Set the range switch to one of the DCA positions. If you do not know the current level to be measured, start at the highest 10A range, then lower the range using the range doubler and range switches. 2. Connect the red test lead to: +10A DC to measure current over 500 mA and under 10A. +V-Ohms-A to measure current of 500 mA or less. 3. Connect the black test lead to the -COM jack. 4. Remove power from the circuit under test and break the circuit at the appropriate point. 5. Connect the test leads in series with the circuit (black lead to the negative side and red lead to the positive side). 6. Apply power to the circuit under test. 7. Set the range doubler and range switches as required to get a reading in the upper 1/2 or 1/3 of the scale. 8. Read the current on the black DC scale. Note: If you set the range doubler switch to V/2.A2, divide the range switch setting by two and read the scale. DECIBEL MEASUREMENTS 1. Plug the black test lead into the -COM jack and the red test lead into the +V-Ohms-A jack. 2. Set the range switch to one of the ACV positions. 3. Connect the test lead tips to the circuit under test. 4. Set the range doubler switch as required to get a reading in the upper 1/2 or 1/3 of the scale. 5. Read the lower black dB scale, adding the appropriate number of decibels to the dB scale as noted on the chart at the lower right of the scale. For example, if the pointer indicates + 12 dB and the range switch is set to 50 AC V and the range doubler switch is set to V/2.A2, add 14 decibels to the indicated value. The result is +26 dB. Note: For the most accurate decibel readings, the circuit impedance must be 600 Ohms. (BR/all-07/11/94)