Radio Shack 22-812, Руководство пользователя

Страница: 26 / 32

26
Making Measurements
5. Reverse the test leads and note
the second reading.
If one reading shows a value and the
other is overrange (
EEEEý< ý< ý< ý<
appears) the
device is good. If
EEEEý< ý< ý< ý<
appears during
both readings, the device is open. If
both values are very small or zero,
the device is shorted.
Notes:
• When you test a silicon-type
semiconductor, the values might
vary depending on the tempera-
ture.
• The values that appear during a
diode check show the actual for-
ward voltage (2.0V max). If the
voltage exceeds 2.0V,
EEEEý < ý < ý < ý <
appears. The meter cannot
check this diode.
Checking Diode Polarity
Many diodes have a stripe or mark on
one side. The marked side of the di-
ode indicates the diode’s cathode or
negative (–) side. The other side is
the anode or positive (+) side.
If a diode is not marked, you can use
your meter to check the diode’s polar-
ity. As you follow the steps under
“Checking Diodes” on Page 25, con-
nect the red test lead to one side,
connect the black test lead to the oth-
er side, then measure and note the
voltage. Then reverse the test leads
and measure and note the second
reading. The side of the diode where
the meter shows a higher voltage us-
ing the red test lead is the anode (+)
side. The side of the diode where the
meter shows
Eý <ý Eý <ý Eý <ý Eý <ý
using the red test
lead is the cathode (–) side.
MEASURING LOGIC
Caution: Do not apply more than 5
VDC between terminals. This could
damage the meter or the circuit being
tested.
1. Rotate the function selector to
LOGIC/Hz
.
2. To select the logic function, press
SELECT
once.
BBBBEEEE
appears.
3. Connect the test leads to the
device you want to check.
BBBBEEEE
appears if the logic is low (the
voltage is lower than 1.0V).
>_ >_ >_ >_
appears if the logic is high (the
voltage is higher than 2.0V) The
actual voltage appears if the
logic is between 1 and 2 V.
MEASURING
FREQUENCY/
DUTY CYCLE/
PULSE WIDTH
The meter can measure frequency
from 10 Hz to 4 MHz and duty cycle
and pulse width with a signal frequen-
cy from 10 Hz to 100 kHz. The ampli-
tude of a signal is not larger than 10V
peak.
1. Rotate the function selector to
LOGIC/Hz
.