Carrying Out Measurements - VOLTCRAFT VC-140 Bedienungsanleitung

h) Display indications and operating mode symbols
h1 Diode test
The value that is displayed during the diode test is the forward
voltage at approx. 1 mA test current. The measuring range rea-
ches here from 0 to approx. 3,0 V.
h2 Negative polarity
If the instrument leads have been mixed up / if there is a nega-
tive polarity, the sign "-" appears in front of the measuring
value.
h3 Transistor test
With the transistor test you measure the hfe parameter

Carrying out measurements

A Direct voltage measurement
Never exceed the max. admissible input quantities.
Max. 600 VDC or VACrms with galvanic separation
from the network in the overvoltage category I or
max. 300 VDC/ ACrms in the overvoltage category II.
Do not touch any circuits or circuit elements if you
are measuring voltages that exceed 25 VACrms or
35 VDC.
Proceed as follows to measure direct voltages:
1. Connect the red instrument lead to the V/ Ohm jack and the
black instrument lead to the COM jack.
2. Set the desired voltage measuring range with the rotary switch. If
you measure direct voltages (V=), you can select among 5 mea-
suring ranges (200 mV-2000 mV-20-200-600).
3. Connect the test probes to the measuring object (load circuit,
etc.).
4. The polarity of the measuring value and the actual measuring
value are indicated in the big display.
32
Make sure, when carrying out a diode test, that the
diode and the circuit, into which it might have been
mounted, are absolutely idle. All the existing capaci-
ties must be discharged.
F Transistor test
The transistor base has not been protected against
overload.
Proceed as follows to measure the amplification of a transistor:
1. Set the rotary switch to "hFE".
2. Put the transistor that is to be tested into the measuring base.
Observe the following aspects:
- observe the connection order (e.g. C-B-E) of the measuring
object (can be found in the transistor comparison table / list).
- There are transistor types that contain base emitter resistances
due to which the measurement may be falsified
- The hFE measuring value is not absolutely accurate. It only
informs you about the fact whether the transistor functions or
not. The real amplification of a transistor depends on its wor-
king current. This multimeter can supply a base current of up to
10 uA, at an Vce of 3 V. The collector current that is flowing
during the measurement is recorded and is then used to deter-
mine the hFE value.
- It is not possible to measure transistors that have been moun-
ted into a circuit.
- It is not possible to measure with this multimeter the hfe value
of FETs or other unipolar transistors.
- Do not use force if the connecting "ends" of the measuring
objects do not fit in the base (too "thick"). Otherwise the base
may be damaged.
37