Auto-Range (220-0174A) Making Measurements Faxback Doc. # 7237 Multimeter TURNING ON THE METER To turn on the meter, set ON/OFF to ON. UNDERSTANDING PHANTOM READINGS If you do not connect the meter's probes to a circuit, and select DC or AC volts, the display might show a phantom reading. This is a wandering effect produced by the meter's high input sensitivity and is normal for most high-quality, high-impedance meters. When you connect the probes to a circuit, a real measurement appears. OVERRANGE INDICATION The following display appears when the measurement exceeds the selected range. If you are measuring volts or amps, disconnect the meter from the circuit you are measuring or change the meter's measuring range. Notes: The meter displays the overrange indication or 0 if it blows a fuse while measuring current. If the meter displays the overrange indication when you measure AC current, and the circuit does not exceed the AC current in the present range, the circuit is exceeding the meter's DC rating. For example, if you try to measure a DC power supply's AC ripple current, the signal has both an AC and DC component. If the DC component exceeds the meter's rating, the meter displays the overrange indication. To measure this current, you must externally block the DC component. The AC current modes do not use an AC coupling capacitor to block DC. Both DC and the AC current flows through the shunt resistance. Too much DC current overpowers the AC component. If you need to measure the AC component of a DC signal, we suggest you use a high-quality capacitor to block the DC component. For normal AC line frequencies, we suggest you use a .47 microF or larger capacitor. MEASURING DC VOLTAGE WARNING: DO NOT TRY TO MEASURE A VOLTAGE GREATER THAN 1000 VOLTS DC AND 750 VOLTS AC (RMS). YOU MIGHT DAMAGE YOUR METER AND EXPOSE YOURSELF TO A SEVERE SHOCK HAZARD. Follow these steps to measure a DC voltage. 1. Set the function control to DC V. mV appears on the display. 2. Plug the black test lead into the meter's -COM terminal and plug the red lead into the meter's + terminal. 3. Connect the black test probe to the COMMON point for the voltage to be measured. Connect the red test probe to the voltage you want to measure. When you measure DC voltages, the minus sign (-) appears if you connect the black test probe to a point in the circuit that has a higher potential than the point where you connect the red test probe. Note: The meter does not measure DC using dBm. If you try to select dBm, the meter switches to AC measurements. MEASURING AC VOLTAGE WARNING; DO NOT TRY TO MEASURE A VOLTAGE GREATER THAN 750 VOLTS AC. YOU MIGHT DAMAGE THE METER AND EXPOSE YOURSELF TO A SEVERE SHOCK HAZARD. Follow these steps to measure AC voltage. 1. Select AC volts by rotating the function control to AC V. V appears on the display. 2. Plug the black test lead into the meter's -COM terminal, and plug the red lead into the meter's + terminal. 3. Connect the probes to the voltage you will measure. 4. To change the display to dBm, press dB. The display shows the reading dBm, and dBm appears. To change the reading back to volts, press dB again. Hint: When you use the meter to probe for a voltage in a high-voltage circuit, do not try to position both probes at the same time. In- stead, clamp the black lead to the neutral or ground circuit lead (usually a bare, green, or white lead) using an insulated Slip-On Alligator Clip (Cat. No. 270-354) and probe for voltages with the red lead. You need to concentrate on only one test probe, so place your free hand in your back pocket or behind your back. This helps prevent you from accidentally touching a hot wire (usually red, black, or blue) with the hand. WARNING: IF YOU CLAMP ON TO A HOT WIRE AND TOUCH A CONNECTED TEST PROBES AT THE SAME, YOU COULD RECEIVE AN ELECTRIC SHOCK. MEASURING AN AC VOLTAGE ON A DC BIAS This meter contains a DC blocking capacitor, which lets AC voltage pass through it, but blocks DC voltages. If the meter is in an AC voltage range, the DC blocking capacitor is enabled. To measure an AC voltage superimposed on a DC voltage source bias, follow the steps on Page 19 and 20. Warning: 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 for commercial or industrial use. If you want to measure 3-phase, line-to- line voltages, please note the following: Because of the dangers inherent when you measure three-phase circuits, we strongly recommend you do not use this meter for such applications. Do not exceed the maximum RMS AC rating (750 VAC). If you choose to make the measurements, use extreme caution. The highest possible voltage is much greater than the voltage between any point in the circuit and ground. To determine line-to-line voltage, measure between the circuit and a known ground point. Then multiply the result by 1.732. For example, if you measure a voltage of 462 volts between a point in the circuit and ground, the possible line-to-line voltage is 800 volts. 462 Volts x 1.732 = 800 Volts This voltage exceeds the meter's range and you should not connect the meter to the circuit or to any equipment connected to the circuit. Doing so could present a dangerous shock hazard and damage the meter. MEASURING AC/DC CURRENT To measure current, break the circuit and connect the leads in series with the circuit. Never connect the leads across a voltage source (in parallel). Doing so can blow the fuse or damage the circuit under test. The maximum current input limit is 10A. WARNINGS: DO NOT APPLY VOLTAGE DIRECTLY ACROSS THE INPUT TERMINALS WHILE IN THE CURRENT MODE. YOU MUST CONNECT THE METER IN SERIES WITH THE CIRCUIT. THE 10A INPUT TERMINAL IS FUSED. A SEVERE FIRE HAZARD AND SHORT CIRCUIT DAMAGE EXIST IF YOU APPLY A VOLTAGE WITH HIGH CURRENT CAPABILITIES TO THIS TERMINAL. YOU ALSO COULD DESTROY THE METER. 1. Set the function control to pulse DC or pulse AC. mA appears on the display. 2. Set the current switch for the desired current range. Note: To measure a current level that exceeds 0.4 amps, you must use the 10A input. 3. Remove power from the circuit under test. Then break the circuit at the appropriate point. 4. Connect the probes in series with the circuit. 5. Apply power to the circuit. If the current is less than the maximum shown for the input jack selected, the meter might down-range for a higher resolution reading. For example, if you measure a 3500 microA current and the current changes to 350 microA, the meter automatically shifts to the 400.0 microA range if the meter is in the auto mode. Notes: If you set the meter for DC current, the minus (-) sign appears or disappears to the left of the bargraph to show the polarity of the measured current. The 400 mA and the 4000 microA ranges are fuse-protected. The 10A range is not fuse-protected. The meter displays the overrange indication or if it blows a fuse while measuring current. If the meter displays the overrange indication when you measure AC current, and the circuit does not exceed the AC current in the present range, the circuit is exceeding the meter's DC rating. For example, if you try to measure a DC power supply's AC ripple current, the signal has both an AC and DC component. If the DC component exceeds the meter's rating, the meter displays the range indication. To measure this current, you must externally block the DC component. The AC current modes do not use an AC coupling capacitor to block DC. Both DC and the AC current flows through the shunt resistance. Too much DC current overpowers the AC component. If you need to measure the AC component of a DC signal, we suggest you use a high-quality capacitor to block the DC component. For normal AC line frequencies, we suggest you use a .47 microF or larger capacitor rated for the voltage involved (500 volts or greater). MEASURING RESISTANCE WARNING: BE SURE THE CIRCUIT UNDER TEST HAS ALL POWER REMOVED AND 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 incircuit resistance, be sure the circuit under test has all power removed (all capacitors are fully discharged). 1. Set the function control to Ohms. Ohms appears on the display. If there is no resistance connected to the meter, the meter sets itself to the highest measurement range if the meter is in the auto mode. When the display shows Mohms, the overrange indication also appears. 2. Plug the red test lead into the + jack and the black test lead into the -COM jack. 3. Connect the probes across the circuit to be measured, or plug the resistor under test into the OHMS/DIODE/CAP socket. If the resistance is greater than 1 megohm, the display takes a few seconds to stabilize. This is normal for high-resistance measurements. Notes: As with the voltage range, use the measuring unit display to determine the current resistance range. If only Ohms appears on the display, the values of the measurements are in ohms. If K and Ohms appear, the meter is measuring kilohms (the reading x 1000). If M and Ohms appear, the meter is measuring megohms (the reading x 1,000.000). The meter has a fuse and a special circuit that protects the resistance ranges from over-voltage (voltages greater than 5 volts). If you blow the meter's fuse, the meter does not operate correctly in the ohms mode. Check the fuse if the meter displays 0 for all resistance measurements, or if it displays other unusual readings. When you touch the ends of the test probes together, the meter selects the 400-ohm scale and displays a small value. This value is the resistance of the test leads. Note this value and subtract it from the measured value when you measure a very small resistance. When you measure resistance greater than 400-kOhms, skin resistance affects the reading. Use the DIODE/OHMS/CAP socket to measure resistors, if possible. If you must hold the resistor and use the leads, be careful not to touch both probes while you take a measurement. Checking Continuity Your meter has a built-in audible continuity function. Follow these steps to check a circuit's continuity. 1. Set the function control to hear sound. CONT and Ohms appear on the display. 2. Connect the red test lead to the + jack and the black test lead to the -COM jack. 3. Connect the probes to the circuit you want to test. Notes: If the circuit's resistance is less than or equal to 50 ohms, the buzzer sounds. If the resistance is greater than 50 ohms, but less than 400 ohms, the meter displays the circuit's resistance and the buzzer does not sound. The meter shows an overrange condition if the resistance is 400 ohms or greater. There is no auto-ranging function in the continuity-check mode. 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. Set the function control to diode-. The diode symbol appears on the display. 2. Plug the red test lead into the + jack and the black test into the - COM jack. 3. Remove power from the circuit under test. 4. Connect the probes to the component you want to check and note the display. Or, connect the component you want to test to the DIODE/OHMS/CAP test socket and note the display. 5. Reverse the probes or reverse the component in the socket, and note the second reading. If one value is normal and the other is overrange, the component is good. If both values are overrange, the component is open. If both values are very small or zero, the component is shorted. Notes: The value indicated by the bar display during the diode check function is the forward voltage (approx. 2.5 max.). When the diode is reverse biased, the display shows the normal overrange indication, but the bargraph show 25. This reading is the actual open-circuit (reverse biased) voltage. (2.45 volts appears as 25 on the bargraph.) If the display shows a low voltage reading, the red test probe is at the anode of the diode and the black probe is at the cathode (banded side) of the diode. This condition is called the forward biased condition. If the diode is in a forward biased condition and if you use the DIODE/OHMS/CAP to test the diode, the anode is at the + side of the socket and the cathode is at the banded (-) side. This meter supplies enough forward voltage to light most LEDS. This lets you determine if an LED is good and which lead is the cathode. CHECKING TRANSISTORS Follow these steps to determine a transistor's pinout, type, and base gain. 1. Disconnect the test leads from the meter. Voltage connections might affect the hFE reading. 2. Plug a transistor into the hFE socket. 3. Set the function control to hFE. hFE appears on the display. The meter displays the transistor type (NpN or PnP) for several seconds. Then the meter displays the transistor's pinout. The three letters it displays correspond to the three terminals of the hFE socket. For example, if the meter displays EbC, the far left lead is the emitter, the middle lead is the base, and the far right lead is the collector. After another short pause, the meter displays the actual hFE of the transistor. This value ranges from 1 to 39,999. The meter continuously displays the hFE, even if you plug another transistor into the socket. To force the meter to examine the transistor type and pinout, press TEST after you plug in the new transistor. Notes: 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. 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, and hFE for power transistors with this meter. The meter displays a default junction type and pinout if you press hFE when you have not connected a transistor. The meter defaults to PnP and CEb with the hFE measurement given as a very value or overflow condition. The bar graph reading is not stable-it ranges up and down while the display maintains a running average of the random readings. 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. Some transistors designed to operate at high frequencies show a small amount of reverse gain (reverse beta). This can make your meter display an incorrect transistor type and pinout. To be sure you have the correct pinout and transistor type, check all transistors twice-once with the transistor's flat side facing you and once with the flat side facing away from you. The reading that indicates the highest gain is the correct reading. Caution: The transistor socket is NOT protected against over-voltage. 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 750 VOLTS AC RMS, YOU MIGHT DAMAGE YOUR METER AND EXPOSE YOURSELF TO A SEVERE SHOCK HAZARD. Follow these steps to measure the frequency of a signal. 1. Set the function control to Hz. K Hz appears on the display. 2. Plug the red test lead into the + jack and plug the black test lead into the -COM jack. 3. Connect the black test probe to a ground reference for the signal, and connect the red test probe to the signal source. The meter displays the measured frequency from 0 to 2.000 MHz. Notes: The meter uses a 1 Hz gate signal to measure the frequency of signals below 4000 Hz. You might have a wait a few seconds for the display to stabilize. For signals above 4000 Hz, you might have to manually set the frequency range to prevent the meter from displaying a harmonic of the actual frequency. See "Manually Selecting the Range." Because measuring frequencies takes several seconds, the keypad might be slow to respond to key presses. Measuring frequencies above 100 kHz might cause BATT to appear on the display. If this happens, switch the meter to another mode. If BATT still appears, the batteries might need to be replaced. MEASURING CAPACITANCE Before you measure capacitance, fully discharge the capacitors. Follow these steps to measure capacitance. 1. Set the function control to Capacitance. nF appears on the display. 2. Plug the red test lead into the + jack, and plug the black test lead into the -COM jack. 3. Attach the red test probe to the capacitor's + side and attach the black test probe to the capacitor's negative side. Or, plug the capacitor into the DIODE/OHMS/CAP socket. (Observe the polarity for electrolytic capacitors.) 4. Read the measured value on the display. Notes: An electrolytic capacitor's measured capacitance changes depending upon the voltage applied to the capacitor. Because this meter cannot use high voltages to set the electrolyte, it cannot measure the absolute capacitance value. The lowest capacitance ranges have an internal capacitance that is the actual input capacitance of the instrument. If you want to make measurements at very low ranges, subtract the internal capacitance from the measurements. USING THE HOLD FUNCTION The hold function lets you freeze the measurement reading on the meter's display. This function is useful when there are many voltage changes and you need a snapshots of the voltage. To use the hold function, connect the test probes to the component or circuit you want to measure. When you want the meter to hold the reading, press DATA HOLD. The reading locks on the display and HOLD appears. In the hold mode, the meter cannot take any more measurements. To clear the hold reading and allow the meter to resume normal operation, press DATA HOLD again. USING THE BAR GRAPH In addition to the numeric display, the meter displays all measurements on a bar graph at the bottom of the display. The bar graph is updated more quickly than the digital display, and gives a better indication of trends for varying measurements. The bar graph has 41 marks. The first mark is always on, and indicates 0. Each additional mark represents the first two digits in the digits in the display. For example, if the displayed value is 1.853, 19 marks appear on the bar graph. For DC functions, a minus sign (-) appears to the left of the bar graph to indicate negative polarity. MANUALLY SELECTING THE RANGE The meter automatically selects the best range for most applications. For some situations, you might want to manually set the range. To switch to the manual mode, press MANUAL/AUTO so A U T O disappears from the display. Then press RANGE DOWN or RANGE UP to select the range. To return to automatic range selection, press MANUAL/AUTO so A U T O appears on the display. USING THE BEEP FUNCTION You can set the meter to beep each time you press a button, turn the function control, or move the current switch. To turn on the beep function, press degree F/degree C. BEEP appears on the display. To turn off the beep function, press degree F/degree C so BEEP disappears. Note: In some modes, the beep does not sound for all controls. USING THE TEMPERATURE FUNCTION You can connect the supplied temperature probe to measure temperature from -58 degrees F to 302 degrees F (-50 degrees C to 150 degrees C). Within the range of 32 degrees F to 212 degrees F (0 degrees C to 100 degrees C), the meter is accurate within 3.6 degrees F (2 degrees C). Outside this range, the meter's accuracy is not specified. WARNING: RISK OF ELECTRIC SHOCK. DO NOT TOUCH HOT (LIVE) CIRCUITS WITH THE TEMPERATURE PROBE. To use the temperature function,set the function control to TEMP degrees F/degrees C. Connect the probe's black test lead to the meter's -COM terminal, and connect the red test lead to the meter's + terminal. Place the probe on the object whose temperature you want to measure. The display shows the object's temperature. To change the display from Fahrenheit (F) to Celsius (C) or vice-versa, press degrees F/degrees C. C or F appears next to the measurement. Note: If a temperature measurement is zero, the display shows only C or F. (LB/all-07/20/94)