Today's security technicians install and repair a wide range of products that require him or her to have the precise tools and testers needed to perform efficiently. Having the correct tools can mean the difference between quickly solving a problem or wasting valuable time.

Take the following quiz to see if you have what it takes to select and use the right tool for the job at hand.

1. When a Volt-Ohm meter (VOM) is set to voltage, its internal resistance is very high.

a. True
b. False

2. When a VOM is set to current, its internal resistance is very high.

a. True
b. False

3. To measure current with a VOM you must

a. connect your meter in series.
b. connect your meter in parallel.
c. disconnect the power source.
d. All of the above
e. None of the above

4. To measure voltage with a VOM you must

a. connect your meter in series.
b. connect your meter in parallel.
c. disconnect the power source.
d. All of the above
e. None of the above

5. When checking for foreign grounds on a circuit, you should disconnect the wiring and place your meter on the

a. highest current scale.
b. lowest current scale.
c. highest resistance scale.
d. lowest resistance scale.

6. When checking the resistance of a protective circuit, with the end-of-line (EOL) disconnected, you should disconnect the wiring and place your meter on the

a. highest current scale.
b. lowest current scale.
c. highest resistance scale.
d. lowest resistance scale.

7. A VOM is the only tool necessary to thoroughly test a CAT 5 cable run.

a. True
b. False

9. Scandisk is a file-compression utility.

a. True
b. False

8. The best tool you can use to locate hidden cables is a

a. digital VOM.
b. analog VOM.
c. tone generator.
d. oscilloscope.

10. The only way to focus a CCTV camera is by using a field monitor.

a. True
b. False

11. You must always insert a meter into a circuit to measure its current.

a. True
b. False

12. A megOhm meter is used to measure circuit resistance.

a. True
b. False

13. A hydrometer is used to measure humidity.

a. True
b. False

14. Which of the following common hand tools is available in a battery-powered version?

a. Drill
b. Hammer-drill
c. Circular saw
d. Reciprocating saw
e. All of the above

15. Which of the following tests should be performed to ensure proper data network cable runs?

a. Shorts
b. Opens
c. Reversed pairs
d. Split pairs
e. All of the above

What's Wrong With This?

One of Wally Larman's clients wanted to increase the amount of battery standby power for his alarm system to 24 hours. To calculate the size of the batteries, Wally needed to measure the amount of current that the control was supplying to the detection devices. He connected his digital VOM as shown in this diagram, but as often happens, he made a mistake. Can you see what Wally did wrong and what he must do to correctly measure the current load?

November 2003 Answers

Here are the answers to the 5-Minute Tech Quiz and What's Wrong with This?

1. a

2. b - The internal resistance of a meter is critical in obtaining an accurate reading. If the resistance of a current meter is too high or if the resistance of a voltage meter is too low, it will result in an inaccurate measurement, because the meter's resistance would combine with that of the circuit being measured.

3. a

4. b

5. c - When testing for foreign grounds on an unknown circuit it is a good idea to first test for the presence of voltage, and then check for resistance. Using the highest resistance scale will allow you to check for highly resistive grounds.

6. d - With the EOL disconnected the resistance of a protective circuit should be very low, so you should set your meter to the lowest resistance scale.

7. b

8. c

9. b - Scandisk is a utility program to check and repair disk problems.

10. b - You can use a video test meter to adjust not only the focus, but also the sync, white (iris) setting, and the video signal level. These meters allow a single person to make all adjustments at the camera without the need to carry a monitor.

11. b - In some cases you can also use a "clamp-on" meter to measure current. These devices allow you to measure the current flow without interrupting the circuit by clamping the probe around one of the wires.

12. b - A megOhm meter is used to test insulation.

13. b - A hydrometer is used to measure the specific gravity of a liquid, while a hygrometer is used to measure humidity.

14. e - The use of battery-powered tools can often increase productivity.

15. e - Due to the high speed of today's data networks it is important that the cables be properly terminated as well as free from any shorts, grounds, and opens. Testers are available that will test all parameters of the cable and connections.

ANSWER to What's Wrong With This?

Wally's problem is that he set his meter to the voltage scale and not to the current scale. Wally should set his meter to current and connect it as shown in this diagram. This will allow him to measure the current draw from the control. Wally then can add this to the current that the control requires, to determine the total current necessary to operate the system. He can then calculate the amount of batteries necessary to provide this current for 24 hours.

Wally also must check the capacity of the control's power supply before connecting the additional batteries to make sure that it can support the increased load. If necessary, Wally may have to add an auxiliary power supply to provide the desired standby time. Remember to check with the manufacturer before adding extra batteries to any control or power supply to prevent overloading.