Page 271 - Electromechanical Devices and Components Illustrated Sourcebook

Chapter 13 Meters 233

Panel Screws

Paper
Voltage Read-Out
Top Panel Curve
1 x 2 #1 Pine Drive Pen
Box Cogs
Screws
0 1 2 3 4 5 6 7 8 9 10 Scale
Manual
Feed DC VOLTS

Range
Selector 1 10 10 Case
.1 100 1 100
+ On
Input Power
Bottom Panel − Switch
Off
Rubber Foot INPUT RANGE SPEED POWER
IPM
Rubber
Foot
Figure 13-31 Bench Built Multimeter Cabinet Assembly
Figure 13-33 Strip Chart Recorder

The probe set shown in Figure 13-32 is made by pressing Circular Chart Recorders
a brass rod, with a wire soldered to one end, into a heavy-wall
plastic tube. After the rod is in place use a file to sharpen the Another type of recording instrument is the circular chart
ends. The opposite ends of the leads are equipped with stan- recorder. These recorders provide the same function as a strip
dard banana plugs. chart unit, except that they are generally used for long-term mon-
itoring. Speeds on the units are usually in hours, days, and/or
weeks. Figure 13-34 shows a typical circular chart recorder.
Solder Joint Sharpen Point Because of the internal mechanism, chart recorders are not
Plastic Tube particularly sensitive. To monitor lower level signals some
3/32 Dia. Brass
sort of amplifier is required. Figure 13-35 shows a strip chart
recorder being driven from the 0-to 10-volt output of an ordi-
nary VTVM.

Test Lead Wire

Voltage
(M) Banana Plugs Curve 7 8 9 10
6
5
4 3
Figure 13-32 Bench Built Multimeter Test Probes 1 2
0
24
1
2 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 Paper
3
4 Read-Out
5
6
8 7
Pen
Strip Chart Recorders Time
Reference
7 Day
1 10 48H 30 Day Case
For applications that require monitoring, a strip chart recorder .1 24H
Range 100
is often used. These instruments are simply a voltmeter with Selector On Speed
Selector
an ink pen replacing the needle. A roll of paper is continuously + −
RANGE INPUT Off SPEED
moved under the pen and a continuous record is maintained. Rubber
Strip chart recorders are generally multirange voltmeters with Foot
Input
a speed range selector to control the paper feed. Figure 13-33 Power Switch
shows a typical strip chart recorder. Figure 13-34 Circular Chart Recorder