Dc Voltage Measurement; Ac Voltage Measurement; Current Measurement - Elenco Electronics M-1007K Assembly And Instruction Manual

DC VOLTAGE MEASUREMENT

Figure 4 shows a simplified diagram of the DC voltage
measurement function. The input voltage divider resistors
add up to 1 megaohm. Each step down divides the voltage
by a factor of ten. The divider output must be within the
range –0.199 to +0.199 volts or the overload indicator will
function. The overload indication consists of a 1 in the most
significant digit and blanks in the remaining digits.

AC VOLTAGE MEASUREMENT

Figure 5 shows a simplified diagram of the AC voltage
measurement function. The AC voltage is first rectified and
passed through a low pass filter to smooth out the
waveform. A scaler reduces the voltage to the DC value
required to give the correct RMS reading.

CURRENT MEASUREMENT

Figure 6 shows a simplified diagram of the current
measurement function. Internal shunt resistors convert the
current to between –0.199 to +0.199 volts which is then
processed in the 7106 IC to light the appropriate LCD
segments. When current in the range of 10A is to be read,
it is fed to the 10A input and does not pass through the
selector switch.
200mV
Volts
900kΩ
2V
90kΩ
20V
9kΩ
200V
900Ω
1000V
100Ω
Common
Figure 4
Simplified DC Voltage Measurement Diagram
Rectifier
Volts
Low Pass
Filter - Scaler
900Ω
100Ω
Common
Figure 5
Simplified AC Voltage Measurement Diagram
200μA
2mA
A
20mA
200mA
10A
10A
Common
Figure 6
Simplified DC Amps Measurement Diagram
-14-
Low Pass
Filter
100mV
REF
Low Pass
Filter
200V
100mV
REF
750V
900Ω
Low Pass
Filter
100Ω
200μA
2mA
20mA
9Ω
200mA
10A
.99Ω
.01Ω
7106
7106
7106
100mV
REF