An indicating voltmeter or test lamp is used when determining the system voltage. It is also used in locating the ground lead and for testing circuit continuity through the power source. They both have a light that glows in the presence of voltage. See Fig. 1-15.
A modern method of measuring current flow in a circuit uses the hook-on voltammeter. See Fig. 1-16. This instrument does not have to be hooked into the
Fig. 1-15 Test devices.
circuit. It can be operated with comparative ease. Just remember that it measures only one wire. Do not clamp it over a cord running from the consuming de- vice to the power source. In addition, this meter is used only on alternating current (AC) circuits. The AC cur- rent will cancel the reading if two wires are covered by the clamping circle. Note how the clamp-on part of the meter is used on one wire of the motor.
To make a measurement, the hook-on section is opened by hand and the meter is placed against the conductor. A slight push on the handle snaps the section shut. A slight pull on the handle springs open the tool on the C-shaped current transformer and releases a conductor. Applications of this meter are shown in Fig. 1-16. Figure 1-16B shows current being measured by using the hook-on section. Figure 1-16C shows the voltage being measured using the meter leads. An ohmmeter is included in some of the newer models. However, power in the circuit must be off when the ohmmeter is used. The ohmmeter uses leads to complete the circuit to the device under test.
Use of the voltammeter is a quick way of testing the air-conditioning or refrigeration unit motor that is drawing too much current. A motor that is drawing too much current will overheat and burn out.
Fig. 1-16 Hook-on volt-ammeter. (A) The volt-ammeter. (B) Correct operation.
- Measuring alternating current and voltage with a single (D) Looping conductor to extend current range of transformer.
Tool Kits
Some tool manufacturers make up tool kits for the refrigeration and appliance trade. See Fig. 1-17 for a good example. In the Snap-on tool kit, the leak detector is part of the kit. The gages are also included. An adjustable wrench, tubing cutter, hacksaw, flaring tool, and ball-peen hammer can be hung on the wall and re- placed when not in use. One of the problems for any re- pair person is keeping track of tools. Markings on a board will help locate at a glance when one is missing. Figure 1-18 shows a portable tool kit. Figure 1-18J shows a pulley puller. This tool is used to remove the
Fig. 1-17 Refrigeration and appliance tools. (A) Servicing manifold. (B) Ball-peen hammer. (C) Adjustable wrench. (D) Tubing tapper. (E) Tape measure. (F) Allen wrench set. (G) 90° adapter service part. (H) Tubing cutter. (I) Thermometer. (J) Flaring tool kit. (K) Knife. (L) Hacksaw. (M) Jab saw. (N) Halide leak detector. (Snap-On Tools)
Fig. 1-18 Air-conditioning and refrigeration portable tool kit.
- Air-conditioning charging (B) Excavating/charging valve. (C) 90 adapter service port.
(D) O-ring installer. (E) Refrigeration ratchet. (F) Snap-ring pliers.
(G) Stem thermometer. (H) Seal re- mover and installer. (I) Test light.
(J) Puller. (K) Puller jaws. (L) Retainer ring pliers. (M) Refrigerant can tapper. (N) Dipsticks for checking oil level. (O) Halide leak detector. (P) Flexible charging hose. (Q) Goggles. (Snap-On Tools)
pulley if necessary to get to the seals. A cart (A) is included so that the refrigerant and vacuum pump can be easily handled in large quantities. The goggles (Q) protect the eyes from escaping refrigerant.
Figure 1-19 shows a voltmeter probe. It detects the presence of 115 to 750 V. The handheld meter is used to find whether the voltage is AC or DC and what the potential difference is. It is rugged and easy to handle. This meter is useful when working around unknown power sources in refrigeration units.
Fig. 1-19 AC and DC voltage probe voltmeter. (Amprobe)
Figure 1-20 shows a voltage and current recorder. It can be left hooked to the line for an extended period. Use of this instrument can be used to determine the exact cause of a problem, since voltage and current changes can affect the operation of air-conditioning and refrigeration units.
Fig. 1-20 Voltage and current recorder. (Amprobe)
