Digital Multimeter (220-0182) Operation Faxback Doc. # 7586 UNDERSTANDING PHANTOM READINGS In some DC and AC voltage ranges, when the probes are not connected to any circuit, the display might show a "phantom" reading. This is normal. The meter's high input sensitivity produces a wandering effect. When you connect the probes to a circuit, accurate reading appears. MEASURING HIGH-VOLTAGE CIRCUITS When you use the meter to check a high-voltage circuit, do not try to position both probes at once. Instead, clamp one probe to the neutral or ground lead of the circuit (usually a bare, green, or white lead in AC wiring circuits) using insulated Slip-On Alligator Clips (Cat. No. 270-354). Then probe for voltages with the other probe. This helps prevents you from accidentally touching a hot wire, because you need to concentrate on only one test probe. Warning: Never clamp onto a hot wire, (usually red, black, or blue in AC wiring circuits). If you clamp onto a hot wire and touch the other probe, you could receive a shock. OVERRANGE INDICATION The following display appears when the measurement exceeds the meter's range. If you are measuring volts or amps, disconnect the meter from the circuit you are measuring or change the meter's measuring range. AC/DC VOLTAGE MEASUREMENT WARNING: DO NOT TRY TO MEASURE A VOLTAGE GREATER THAN 1000 VOLTS DC OR 750 VOLTS AC. YOU MIGHT DAMAGE YOUR METER AND EXPOSE YOURSELF TO A SEVERE SHOCK HAZARD. Note: All the figures on the display blink when more than the maximum voltage (DC 1000/AC 750 VOLTS) is supplied. If this happens, DISCONNECT THE PROBES IMMEDIATELY. Follow these steps to measure AC/DC Voltage: 1. Rotate the function selector to the desired ACV/DCV position. Select the range as required for the voltage level to be measured. If you do not know the voltage level, start with the range switch set to the highest voltage position and reduce the setting as needed to get a reading. 2. Plug the black probe into the meter's COM terminal and the red probe into the meter's V-ohms terminal. 3. Connect the probes to the AC/DC voltage source you want to measure. The voltage appears on the display. Notes: If polarity is negative, a "-" appears on the left of display. For the most accurate measurement, select the lowest voltage range possible without getting an overload reading. Measuring an AC Voltage on a DC Bias To measure an AC voltage superimposed on a DC voltage source bias, follow the steps for measuring AC voltage. Caution: Never try to measure an AC voltage that is riding on a DC voltage level where the peak AC voltage exceeds 1000V with respect to earth ground. MEASURING 3-PHASE AC VOLTAGES We designed this meter to measure household AC voltage. It is not intended for commercial or industrial use. If you want to measure 3- phase, line-to-line voltages, please note the following. Warning: Because of the dangers inherent in measuring three-phase circuits, we strongly recommend that you do not use this meter for such applications. If you choose to make the measurements, use extreme care. The actual voltage can be greater than the circuit's rated voltage (line-to- ground). To determine the line-to-ground voltage, multiply the rated line-to- ground voltage by 1.732. For example, if the rated voltage is 462 volts, the line-to-line voltage is. 462 Volts X 1.732=800 Volts This voltage exceeds the meter's range and you should not connect the meter to this circuit. See "Measuring High-Voltage Circuits". Measuring AC/DC CURRENT Warnings: DO NOT APPLY VOLTAGE DIRECTLY ACROSS TERMINALS. YOU MUST CONNECT THE METER IN SERIES WITH THE CIRCUIT. THE 20A TERMINAL IS NOT FUSED. A SEVERE FIRE HAZARD AND SHORT CIRCUIT DANGER EXISTS IF YOU APPLY A VOLTAGE WITH HIGH-CURRENT CAPABILITY TO THIS TERMINAL. THE METER CAN BE DESTROYED UNDER SUCH CONDITIONS. To measure current, break the circuit and connect the probes to two circuit connection points. Never connect the probes across a voltage source in parallel. Doing so can blow the fuse or damage the circuit under test. Note: The maximum input current is 2A or 20A depending on the terminal used. In the 2A range, excessive current blows the fuse, which you must replace. The 20A range is NOT protected by the fuse- excessive current can destroy the meter. 1. Rotate the function selector to the desired AC A or DC A range. If you do not know the current level, set it to the highest position and reduce the setting as needed to get a reading. 2. Plug the back probe into your meter's COM terminal, and the red probe into your meter's A or 20A terminal. 3. Remove power from the circuit under test and then break the circuit at the appropriate point. 4. Connect the probes in series with the circuit. 5. Apply power and read the current. Your meter displays the current value. Note: If you set the meter for DC current, - appears or disappears to indicate the polarity of the measured current. MEASURING CAPACITANCE Follow these steps to measure normal capacitance: Discharge each capacitor before testing by shorting its leads together. Use caution when handling some capacitors, as they can be charged with considerable electricity. Caution: If you attempt to measure the capacitance of a charged capacitor, you might damage your meter. 2. Rotate the function selector to the desired CAP range. If you do not know the approximate capacitance value, set the range to the highest position and reduce the setting as required to get a valid reading. The display shows a residual value. To obtain a 000 display, press LOGIC REL. 3. Insert the discharged capacitor into the CAP + and - clips connectors. Your meter displays the capacitance value. Note: For polarized capacitors, be sure to insert the negative lead in the lead in the - clip. MEASURING RESISTANCE Warning: NEVER CONNECT THE TEST PROBES TO A SOURCE OF VOLTAGE WHEN YOU HAVE SELECTED THE OHMS FUNCTION AND PLUGGED THE PROBES INTO THE V-OHMS TERMINAL. BE SURE THAT THE CIRCUIT UNDER TEST HAS ALL POWER REMOVED AND THAT ANY ASSOCIATED CAPACITORS ARE FULLY DISCHARGED BEFORE YOU MAKE A RESISTANCE MEASUREMENT. The resistance measuring circuit compares the voltage gained through a known resistance (internal) with the voltage developed across the unknown resistance. So, when you check in-circuit resistance, be sure the circuit under test has all power removed (all capacitors are fully discharged). 1. Plug the black probe into your meter's COM terminal and the red probe into your meter's V - ohms terminal. 2. Rotate the function selector to the desired ohm range. 3. Connect the probes to the device you want to measure. Your meter displays the resistance value. Notes: If the measured resistance value exceeds the maximum value of the range selected, OL displays to indicate overload and the bar graph flashes. Select a higher range. In this mode, the beeper does not sound. When you short the test probes in the 200ohms range, your meter displays a small value (no more than 0.3 ohms). This value is due to your meter's internal resistance measurements. To obtain 000 display at this time, press LOGIC REL on the meter while shorting the test leads. For resistance of approximately 1 Megohm and above, the display might take a few seconds to stabilize. This is normal for high resistance readings. CHECKING DIODES This function lets you check diodes and other semiconductors for opens and shorts. It also lets you determine the forward voltage for diodes. You can use this function when you need to match diodes. 1. Plug the black probe into your meter's COM terminal and the red probe into your meter's V-ohms terminal. 2. Rotate function selector to the >|music note. 3. Connect the probes to the diode you want to check and note the meter reading. If the display shows a value, for example 0.2 for germanium diode or 0.5 for a silicon diode, reverse the diode. If the meter indicates an overrange, the diode is good. The displayed number is the diode's actual forward voltage (up to 2.5 volts). If the display indicates an overrange condition, reverse the polarity of the connection. If the display shows a value, the device is good. The displayed value is the component's actual forward voltage (up to 2.5 volts). If the display still indicates an overrange condition, the device is open. If the display shows a value both before and after you reverse the polarity, the device is shorted or the meter's 1/18 amp fuse is blown. When you connect the diode to the meter and the meter displays the device's forward voltage, the red test probe or >|music notes socket is connected to the diode's anode, and the black probe or >|music notes socket is connected to the diode's cathode. This meter supplies enough forward voltage to light most LEDs. However, if the LED's forward voltage is greater than 2.5 volts, the meter incorrectly indicates that the device is open. The bar graph shows a maximum reading of 24, even during an overrange. CHECKING CONTINUITY Follow these steps to check a circuit's continuity: 1. Rotate the function selector to >|music note. 2. Plug the black probe into your meter's COM terminal and the red probe into your meter's V-ohms terminal. 3. Remove power from the circuit. Warning: Never perform a continuity measurement on a circuit that has power connected. 4. Connect the probes to the circuit. Note: The buzzer sounds if the measured resistance is below 30 ohms. CHECKING TRANSISTORS Follow these steps to determine a transistor's base gain: 1. Rotate the function selector to the hFE position. 2. Insert the transistor you want to measure into the appropriate transistor socket. Your meter displays the transistor's hFE value. Notes: Insert the base, collector, and emitter pins in the correct sockets, as marked. Do not take the hFE reading as an absolute measurement, but rather as an indication that the transistor is operating. The true gain of a transistor depends on its operating current. This meter applies 500 to 1000 microA to the emitter and collector and measures the base current to calculate the base gain. Even though the meter turns off the test probes during the hFE measurement, a voltage connection might affect the hFE reading. Do not connect the test probes to a voltage source during this measurement. You cannot measure the hFE of a transistor that is connected in a circuit. You cannot measure the hFE of an FET or other non-bipolar transistor. Some power Darlington transistors contain internal base-to-emitter resistors. Because the meter uses two current readings to calculate hFE, any internal transistor resistance causes undependable readings. High-voltage junctions in power transistors prevent correct readings. Also, the larger leads of the power transistor can damage the test socket. Do not try to determine type, pin-out, or hFE for power transistors with this meter. hFE is affected by temperature. Try not to warm the transistor with your hand when you install the device in the socket. If the hFE reading is not stable when you first measure it, let the transistor's temperature stabilize. Warning: The transistor socket is not protected against overload. You can damage the meter and void your warranty if you build and use external leads for the transistor socket. MEASURING FREQUENCY WARNING: IF YOU TRY TO MEASURE THE FREQUENCY OF A SIGNAL THAT EXCEEDS 250 VOLTS AC RMS, YOU MIGHT DAMAGE YOUR METER AND EXPOSE YOURSELF TO SEVERE SHOCK HAZARD. Follow these steps to measure the frequency of a signal: 1. Rotate the function selector to the FREQ range. 2. Plug the black probe into your meter's COM terminal and the red probe into your meter's V-ohms terminal. 3. Connect the probe to the frequency source. Notes: When the test probes are connected to an AC outlet, do not turn the function selector switch to another range. It may damage the internal components, or you. Overload Protection: 250V DC/AC RMS LOGIC TEST The logic function lets you easily check digital circuits to determine the logic state of different parts of the circuit. Rather than display an absolute voltage, this function displays HI, LO, or --- to indicate logic high, logic low, or undetermined, respectively. Follow these steps to perform a logic test: 1. Rotate the function selector to the logic range. rdy appears on the display. 2. Plug the black probe into your meter's COM terminal and the red probe into your meter's V-ohms terminal. 3. Connect the black probe to the ground point (GND) of the test circuit and the red probe to the supplying voltage point (V+). While keeping the test probes firmly connected to each point, press LOGIC REL. 4. While keeping a connection between the black probe and the circuit's GND point, move the red probe to the other desired points. The meter immediately displays one of the 3 modes, as follows: If value exceeds 70% of the stored (V+) value, HI (HIGH) appears. If value falls below 30% of the stored (V+) value, Lo (LOW) appears. If value is between 30% and 70%, the --- segment appears. Notes: In this mode, the Data-Hold and Max/Min-Hold functions do not work. The supplying voltage from 0.5V up to 19.9V is limited for testing logic. USING THE MAX/MIN MEMORY FUNCTION The MAX/MIN button holds a recorded value on the display, records the maximum value currently measured, and/or records the minimum value currently measured. Follow these steps to store the readings: 1. Press MAX/MIN. The meter displays MAX and displays the highest measured reading. The meter updates the display as the reading changes. Even though the meter only displays MAX, it stores both the maximum and minimum readings. 2. To display the minimum measured reading, press MAX/MIN again. The meter displays MIN and the lowest measured reading. The meter updates the display as the reading changes. Even though the meter only displays MIN, it stores both the minimum and maximum readings. Notes: You cannot use the MAX/MIN mode and the relative mode at the same time. If you select the relative mode, the MAX/MIN function turns off. If the relative mode is already active, the meter ignores the MAX/MIN key. The meter exits MAX/MIN mode if you try to measure a value that is outside the currently set range or if you manually change the range. USING DATA HOLD The data hold function lets you hold the current reading on the meter's display. During any reading, press D-HOLD to prevent changes in the measured value from updating the display. The meter displays HOLD. Press D-HOLD again to resume normal operation. USING THE RELATIVE FUNCTION The relative feature lets you set a reference measurement and measure additional values relative to the reference. For example, if you set the reference at 100 ohms, the meter displays a 123 ohm resistor at 23 ohms, and displays a 75 ohms resistor as -25 ohms. Follow these steps to set a reference: 1. Make a reference measurement. 2. While you measure the reference value, hold down LOGIC REL for about 2 seconds. The meter beeps. After 2 seconds, the meter displays REL and sets the reading to 000. The meter displays additional measurements relative to the reference value. The meter displays additional measurements relative to the reference value. Note: You cannot use the MAX/MIN mode and relative mode at the same time. USING THE METER WITH A COMPUTER INTERFACING THE METER WITH A COMPUTER Follow these steps to interface the meter with a computer: 1. Connect the RS-232C cable between the meter's and computer's serial ports. 2. Turn on the meter. USING THE SUPPLIED SOFTWARE The supplied software runs on PC-compatible computers only. Follow these steps to use the supplied software: 1. Place the diskette in the drive. Copy the files from the diskette to the computer's hard drive or make a back-up copy of the diskette to use. 2. Type Enter. Note: The software automatically defaults to color monitors. 3. To stop execution or to escape from a device I/O error status, press CTRL+BREAK on the computer at the same time. Notes: You must turn off the meter's COM switch when transmitting data to the computer. Do not activate the meter's COM function and the computer's transmission commands at the same time. To release the COM function, turn the range switch or press COM. COM disappears. HINTS FOR WRITING YOUR OWN SOFTWARE If you write you own program, you must include these steps: 1. The host computer must give the meter the D command to activate data transmission. 2. The host computer must give the meter the C Memory-Clear command to clear memories on the meter. 3. The host computer must give the meter the M Memory-Call command to transmit the memories on the meter to the software. Data Format The data format consists of a frame of 14 bytes. The frames are set as follows: BYTE) 1 2 3 4 5 6 7 8 9 A B C D E Ex. 1) DC-1. 9 9 9 9 V CR Ex. 2) 1. 9 9 9 9 M o h m CR The following program is an example of a BASIC program that gets a single reading from the meter: 10 OPEN "COM 1: 1200, N, 7, 2, RS, CS, DS, CD" AS #2 20 A$="D" 30 PRINT # 2, A$ 40 IN$=INPUT$(14, #2) 50 PRINT IN$ 60 CLOSE #2 70 END Communication parameters Transmission rate: 1200 baud Character coding : 7-bit ASCII Parity : NONE Stop Bits : 2 REPLACING THE FUSE WARNING: TO AVOID ELECTRIC SHOCK, DISCONNECT THE TEST PROBES BEFORE REMOVING THE BATTERY OR THE FUSE. REPLACE ONLY WITH THE SAME TYPE OF BATTERY OR FUSE. DO NOT REMOVE THE TOP COVER. SERVICE SHOULD BE PERFORMED ONLY BY QUALIFIED PERSONNEL. CAUTION: FOR CONTINUED PROTECTION AGAINST FIRE OR OTHER HAZARD, REPLACE ONLY WITH A 2A 250 V FUSE. Follow these steps to replace the fuse: 1. Set power to OFF and disconnect the test probes. 2. Remove the back cover by unscrewing the four screws and pulling off the meter's cover. 3. Remove the blown fuse. 4. Install the new fuse in the fuse compartment. 5. Replace the back cover and secure it with the screws. WARNING: DO NOT OPERATE YOUR METER UNTIL THE BACK COVER IS IN PLACE AND FULLY CLOSED. (lb/all-9/19/94)