DIODE CHECK
RANGE RESOLUTION MAX TEST CURRENT MAX OPEN CIRCUIT VOLTAGE
DIODE 1mV 1.4mA 2.8V
TRANSISTOR hFE TEST
RANGE TEST RANGE TEST CURRENT TEST VOLTAGE
NPN/PNP 0 - 1000 Ib = 10μA Vce 3V
-15-
SPECIFICATIONS
GENERAL
DISPLAY 3 1/2 digit LCD, with polarity
OVERRANGE INDICATION 3 least significant digits blanked.
MAXIMUM COMMON MODE
VOLTAGE 500V peak.
STORAGE ENVIRONMENT –15
O
C to 50
O
C.
TEMPERATURE COEFFICIENT (0
O
C to 18
O
C and 28
O
C to 50
O
C)
less than 0.1 x applicable accuracy
specification per
O
C.
POWER 9V alkaline or carbon zinc battery.
DIMENSIONS 128 x 75 x 24mm.
DC VOLTAGE
RANGE RESOLUTION ACCURACY
200mV 0.1mV +
0.5% rdg + 2d
2V 1mV +0.5% rdg + 2d
20V 10mV +0.5% rdg + 2d
200V 100mV +0.5% rdg + 2d
1000V 1V +
0.5% rdg + 2d
MAXIMUM ALLOWABLE INPUT 1000VDC or peak AC.
INPUT IMPEDANCE 1MΩ.
DC CURRENT
RANGE RESOLUTION ACCURACY
200μA0.1μA+1.8% rdg + 2d
2mA 1μA+
1.8% rdg + 2d
20mA 10μA+
1.8% rdg + 2d
200mA 100μA+
2% rdg + 2d
10A 10mA +
2% rdg + 3d
OVERLOAD PROTECTION .2A/250V fuse (mA input only).
AC VOLTAGE
RANGE RESOLUTION ACCURACY
200V 100mV +2% rdg + 10d
750V 1V +2% rdg + 10d
MAXIMUM ALLOWABLE INPUT 750Vrms.
FREQUENCY 50 - 500Hz.
RESISTANCE
RANGE RESOLUTION ACCURACY
200Ω 0.1Ω +
1% rdg + 10d
2kΩ 1Ω +
1% rdg + 10d
20kΩ 10Ω +
1% rdg + 10d
200kΩ 100Ω +1% rdg + 10d
2000kΩ 1kΩ +
1% rdg + 4d
MAXIMUM OPEN CIRCUIT VOLTAGE 2.8V.
RESISTANCE MEASUREMENT
Figure 7 shows a simplified diagram of the resistance measurement
function. A simple series circuit is formed by the voltage source, a
reference resistor from the voltage divider (selected by the selector
switches), and the test (unknown) resistor. The ratio of the two resistors
is equal to the ratio of their respective voltage drops. Therefore, since
the value of one resistor is known, the value of the second can be
determined by using the voltage drop across the known resistor as a
reference. This determination is made directly by the A/D converter.
Overall operation of the A/D converter during a resistance
measurement is basically as described earlier with one exception. The
reference voltage present during a voltage measurement is replaced by
the voltage drop across the reference resistor. This allows the voltage
across the unknown resistor to be read during the read period.
hFE MEASUREMENT
Figure 8 shows a simplified diagram of the hFE measurement function.
Internal circuits in the 7106 IC maintain the COMMON line at 2.8 volts
below V+. When a PNP transistor is plugged into the transistor socket,
base to emitter current flows through resistor R1. The voltage drop in
resistor R1 due to the collector current is fed to the 7106 and indicates
the h
FE of the transistor. For an NPN transistor, the emitter current
through R2 indicates the h
FE of the transistor.
Figure 7
Simplified Resistance Measurement Diagram
Ω
900kΩ
Te st
Resistor
100Ω
900Ω
2000Ω/Dio
200Ω
7106
Reference
Voltage
Low Pass
Filter
Voltage
Source
Common
90kΩ
9kΩ
2000kΩ
20kΩ
200kΩ
Figure 8
R1
Common
R3
R2
PNP
NPN
7106
100mV
Ref.
Low Pass
Filter
V+
EC
CE
BB
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