Page 272 - Electromechanical Devices and Components Illustrated Sourcebook

234 Electromechanical Devices & Components Illustrated Sourcebook

Vacuum Tube Voltmeter
Strip Chart Recorder
4 5 6
3 7
2 8
0 1 20 0 40 50 60 70 9 10
10 80 90
5
0 3 4 50 60 6 7 8 100
1 10 20 2 0 40 70 80 9
0 90100 10
OHMS 0 -1 0 5 20 OHMS
−2 DB
On
Zero Adjust Power Off 0 1 2 3 4 5 6 7 8 9 10
OFF .01 DC VOLTS
Amps OHMS 10M .1
1M 1
uA AC uV
100K 10
DC uV AC VOLTS 10K 100 1 10 10
DC VOLTS 1K .1 100 1 100 On
Function Range +
GROUND −
INPUT OUTPUT Off
INPUT RANGE SPEED POWER
IPM
Signal to be
Monitored
Figure 13-35 Using a Strip Chart Recorder with a Vacuum Tube Voltmeter

Meter Accessories Alligator Clip
Test Lead Wire
A basic probe set is by far the most important accessory that
Tip Safety
any meter can have. An ordinary probe set, as shown in Resistor Ground
Figure 13-32, can be built or purchased and will provide suit- Housing
able performance for most situations. A better choice is a 25 k volt Max.
commercial set with interchangeable tips, as shown in
Figure 13-36. The variety of tips provides better access to Handle
Output
intricate circuits and hands-off use.
Co-Axial Cable
Dual Banana Plug
Figure 13-37 High-Voltage Probe
Spade Lug

Spring Hook
Threaded Stud HD Alligator Clip read 8 volts. Before using a high-voltage probe, it should be
carefully inspected for any damage and should be clean. If the
Standard Alligator Clip
probe is damaged in any way, it should be immediately dis-
Safety Lip
High Density Alligator Clip
Bend Relief carded. A high-voltage probe with even a small crack in the
Insulation Piercing Probe
housing can be lethal. Always follow the manufacturer’s rec-
Standard Probe ommendations when using high-voltage probes.
A clamp-on AC current probe, as shown in Figure 13-38,
is an excellent accessory for any multimeter. These units
Test Lead Wire make reading current very easy. Simply clamp the jaws
around the wire to be surveyed and read the voltage on the
meter. Generally, these units output 1 volt per amp. It should
(M) Banana Plugs
be noted that at maximum current, the voltage at the banana
Figure 13-36 Multi Purpose Test Probe Set
plugs can be dangerously high and great care should be taken
not to disconnect the probe from the meter while the head is
clamped onto a cable.
The high-voltage probe shown in Figure 13-37 is used to Figure 13-39 shows a schematic representation of a current
gauge voltages in excess of the meter’s range. These probes probe. The jaw set is actually the core of a transformer. The
use a dropping resistor in the head of the body that generally primary is the cable being measured and the secondary pro-
drops the output voltage to 1 volt per 1000. That is to say that vides the output signal. It should be noted that if the cable is
if the probe is connected to an 8000-volt source the meter will looped twice around the core, the output voltage will double.