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  5. Owner's Manual

Radio Shack 22-178 Owner's Manual - Features

Manual is about: auto-ranging lcd digital multimeter

Summary of 22-178

  • Page 1

    Cat. No. 22-178 owner’s manual please read before using this equipment. Auto-ranging lcd digital multimeter 22-178.Fm page 1 friday, august 6, 1999 11:38 am.

  • Page 2

    2 this symbol is intended to alert you to the presence of unin- sulated dangerous voltage within the product’s enclosure that might be of sufficient magnitude to constitute a risk of electric shock. Do not open the product’s case. This symbol is intended to inform you that important operat- ing and ...

  • Page 3: Features

    3 features your radioshack auto-ranging lcd digital multimeter is a portable 3 3 / 4 -digit, compact multimeter that is ideal for field, lab, shop, bench, and home applications. Here are some features that make your new digital multimeter a real pro. Latest ic and display technology — ensures reliab...

  • Page 4

    4 data hold function — holds the display so you can see the reading even after you disconnect the probes. Overload and transient protection — helps protect the meter from overvoltage in most ranges. Continuity buzzer function — lets you quickly hear if there is continuity in a cable or between two p...

  • Page 5: Contents

    5 contents a word about safety .................................................. 6 specifications ............................................................. 8 special panel markings ............................................ 12 preparation .........................................................

  • Page 6: A Word About Safety

    6 a word about safety we have taken every precaution in designing this meter to ensure that it is as safe as we can make it. But, safe operation depends on you, the operator. We recommend that you follow these simple safety rules: • never apply voltages to the meter that exceed the limits given in t...

  • Page 7

    7 • because many ac/dc sets have a potentially hot chassis, be sure the top of your workbench and the floor underneath it are made of non-conductive mate- rials. • the multimeter is fully calibrated and tested. Under normal use, no further adjustment should be neces- sary. If the meter requires repa...

  • Page 8: Specifications

    8 specifications display .................................... Lcd 3 3 / 4 -digits maximum, 3200 count resolution bar graph ................................................... 33 segments (100 counts of resolution/segment sampled 12 times/second) ranges and accuracy dc volts 300 mv–3 v .................

  • Page 9

    9 dc current 300 m a/30 ma .................................... ± 1.0% of reading, ± 0.2% of full scale, ± 1 in last digit 3000 m a/300 ma ..................................... ± 1.5% of reading, ± 0.2% of full scale, ± 1 in last digit 20 a .................................................... ± 4.0%...

  • Page 10

    10 resistance 300 ohms–3–30–300 kohms ............... ± 1.0% of reading, ± 0.2% of full scale, ± 1 in last digit 3 m ohms ............................................ ± 2.0% of reading, ± 0.2% of full scale, ± 1 in last digit 30 m ohms ..................................................± 3.5% of read...

  • Page 11

    11 overrange indication ............. Ol. (overload) appears on the display to indicate that the measurement exceeds the absolute maximum reading. Use care in dc1000v, ac 750 v, and dc/ac 20 a ranges, as exceeding the maximum limits of these ranges can dam- age the meter and prevent an overrange ind...

  • Page 12: Special Panel Markings

    12 special panel markings for your safety, we have added special markings to the panel to remind you of the measurement limitations. 20 a the maximum current that you can mea- sure at this terminal is 20 amps. Max 1kv to avoid electrical shock or instrument damage, do not connect the common input te...

  • Page 13: Preparation

    13 preparation installing batteries your meter requires two aa batteries for power. We rec- ommend alkaline batteries, such as radioshack cat. No. 23-557. 1. Turn off the power and disconnect the test leads. 2. Remove the meter from the holster. 3. Use a phillips screwdriver to remove the screw that...

  • Page 14

    14 6. Replace the meter in the holster. When appears on the right side of the display, re- place the batteries. Warnings: • to avoid electrical shock, disconnect both test leads from any equipment before you remove the batteries. • do not operate the meter until you replace the batter- ies and close...

  • Page 15

    15 caution: although these test leads are rated for 1200 volts, the maximum rating of this meter is 1000 volts dc/ 750 volts rms ac. Do not try to measure any voltage greater than 1000 volts dc/750 volts rms ac. Using alligator clips alligator clips are supplied to allow you to keep your hands free ...

  • Page 16

    16 using the stand and holster the fold-out stand lets you place the meter upright on a flat surface for easier viewing. The holster lets you hang the meter on a wall, hold the test leads, and protect the meter from damage if you drop it. (illus of meter w/stand and hanging) 22-178.Fm page 16 friday...

  • Page 17: Using The Meter

    17 using the meter before you use the meter the first time to make a mea- surement, follow these steps to confirm correct operation and to familiarize yourself with the meter’s operation. 1. Press power to turn on the meter. All the display elements briefly appear. 2. Set the selector to v . 3. Pres...

  • Page 18

    18 notes: • see the unit of measure on the display to distinguish the range. For example, the meter displays mv in the 300 mv range and v in the 300 v range. Also, note the position of the decimal. For example, if the dis- play shows .000v , the meter is set to measure less than 1 volt. If the displ...

  • Page 19

    19 connect the red lead to the v•w• •ma•ma• terminal and the black lead to the com terminal. All connections except 20 a measurements are made at these terminals. Caution: when ol. (overload) appears on the display, the value you are measuring exceeds the meter’s maxi- mum range. This is a normal di...

  • Page 20

    20 manually setting the range when you measure voltages or resistance, your meter can automatically select a measuring range. When you measure current, the meter automatically selects a range within the limits of the selector’s setting. While this fea- ture is convenient, it might be faster to manua...

  • Page 21

    21 to cancel data hold, press data-h again or move the se- lector. Using the bar graph the meter also indicates all the measurements on the bar graph at the bottom of the display. The bar graph’s length increases and decreases with the measured val- ue. You can easily observe changes in measurements...

  • Page 22: Making Measurements

    22 making measurements measuring dc/ac voltage caution: the maximum input limit for voltage measure- ment is 1000v dc and 750v ac (rms). If you try to mea- sure a dc voltage above 1000 volts or an ac voltage above 750 volts rms, you can damage your meter. When you connect the meter to a voltage high...

  • Page 23

    23 hint: when you use the meter to probe for a voltage in a high-voltage circuit, we recommend you do not try to position both probes at once. Instead, use one of the supplied insulated alligator clips to clamp one lead to the circuit’s neutral or ground lead (usually a bare, green, or white lead in...

  • Page 24

    24 measuring an ac voltage riding on a dc source bias to measure an ac voltage superimposed on a dc volt- age source bias, you must first measure the dc and ac voltages separately, then compute the peak voltage us- ing the formula: ac voltage peak voltage = dc voltage + —————— .707 1. To measure the...

  • Page 25

    25 measuring three-phase ac voltage we designed this meter primarily to measure household ac voltages. It is not intended for commercial or industri- al use. Please note the following about 3-phase, line-to- line voltages. Warnings: • because of the dangers inherent in measuring three- phase circuit...

  • Page 26

    26 measuring dc/ac current to measure current, you must break the circuit and con- nect the leads to two circuit connection points. The con- nection must be in series with the circuit under test. Use the supplied alligator clips for this connection. The maxi- mum input limit for dc/ac current measur...

  • Page 27

    27 3. Plug the black test lead into the com jack and the red test lead into the appropriate jack. 4. Remove power from the circuit under test and dis- charge all capacitors. 5. Break the circuit at the appropriate point. 6. Connect the probes in series with the circuit. 7. Apply power and read the c...

  • Page 28

    28 measuring resistance the resistance-measuring circuit compares the voltage gained through a known resistance (internal) with the voltage developed across an unknown resistance. 1. Remove all power from the circuit under test and dis- charge all capacitors. 2. Set the selector to w . Caution: neve...

  • Page 29

    29 caution: the meter has a circuit to protect the resistance range from over-voltage (450 volts rms ac, 1 minute). However, to prevent accidentally exceeding the protec- tion circuit’s rating and to ensure a correct measurement, never connect the probes to a source of voltage when you set the selec...

  • Page 30

    30 2. Press so appears on the display. Caution: never connect the probes to a source of voltage while the selector is set to . 3. Plug the red test lead into the v•w• •ma•ma• jack and the black test lead into the com jack. 4. Connect the probes to the circuit you want to check. 5. If the circuit res...

  • Page 31

    31 3. Plug the red test lead into the v•w• •ma•ma• jack and the black lead into the com jack. 4. Remove power from the circuit under test and dis- charge all capacitors. 5. Connect the probes to the semiconductor device you want to check and note the meter reading. 6. Reverse the probes and note the...

  • Page 32: Maintenance

    32 maintenance your radioshack auto-ranging lcd digital multimeter is an example of superior design and craftsmanship. The following suggestions will help you care for the meter so that you can enjoy it for years. • keep the meter dry. If it gets wet, wipe it dry immedi- ately. Liquids can contain m...

  • Page 33

    33 modifying or tampering with your meter’s internal compo- nents can cause a malfunction and might invalidate the meter’s warranty. If your meter is not performing as it should, take it to your local radioshack store for assis- tance. Fuse replacement warning: to avoid electric shock, discon- nect ...

  • Page 34

    34 follow these steps to replace any blown fuse. 1. Turn off the power and disconnect the test leads. 2. Remove the screw securing the back case and lift off the back cover. 3. Remove the blown fuse. 4. Replace the fuse with the spare fuse or a new fuse of the same rating. 5. Replace the back cover ...

  • Page 35: Notes

    35 notes 22-178.Fm page 35 friday, august 6, 1999 11:38 am.

  • Page 36

    Radioshack a division of tandy corporation fort worth, texas 76102 8a6 printed in korea radioshack limited warranty this product is warranted against defects for 90 days from date of pur- chase from radioshack company-owned stores and authorized radioshack franchisees and dealers. Within this period...