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O p e r a t i o n o f t h e H M 8 0 1 8
To obtain a deviation in % proceed as follows:
1) Connect the component corresponding to the
reference value.
2) Store the value (memory A) by pressing on the
STORE key, then press the A key.
3) Store the same value (memory B) by pressing
on the STORE key then press the B key.
4) Press the A key then the B key. The -A and ÷B
LED indicators light up. The display shows the
value 100*(Measure – A)/B in %, with a 0.01%
resolution.
In any case the percentage result can not exceed
the -100.00% / +999.99% limits.
Component to test connexion
The components to test can be connected in two
different ways to the HM8018. Two 4 mm banana
jacks are available for a quick measurement. The
tested object is either plugged in or fixed below
the screw type terminals. However this quick
method is not always accurate enough. To perform
high accuracy measurement it is recommended
to use the HZ18 Kelvin Test Leads offered in our
accessories range. This probe uses a Kelvin con-
nexion which minimizes the parasitic impedances.
After changing the connection configuration it is
necessary to perform an open/short calibration.
This point also is valid when changing frequency
from the extreme ranges.
REMARK: When a measurement is in progress,
especially for high impedances, keep your hands or
any other object away from the test connector be-
cause the measurement accuracy may be affected.
Open/short compensation
The parasitic impedance compensation from the
connection system to the device to test is perfor-
med by an open and short calibration. This allows
cables and other parasitic capacitance impedance
compensation. Calibration is performed for the
current frequency. It is better to perform the open/
short calibration in the same conditions like the
component measurement will be made, trying to
do not change the lead positions. In other respects
keep any objects away from the test connection, as
your hands or metallic parts which could influence
measurement.
24
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To perform an open or short calibration:
–
Press on the CAL key. The display indicates
OP.-Sh. The leds –A and AUTO are blinking.
Press the AUTO key to start the short circuited
–
calibration; the measuring cables have to be
conected
–
Press the –A key to start the open circuit
calibration; the measuring cables have to be
disconected
The process lasts few seconds, then the PASS
message is displayed if the process has been
successful, in the opposite case the FAIL message
will be displayed. Short circuit calibration is valid
if the impedance is below 15Ω and if the resistance
is below 10Ω. Open circuit calibration is valid if the
impedance above 10kΩ.
Default settings
To press on the CAL key
dEFLT message appears allows to initiate the
instrument with the factory default configuration.
This function will not modify the calibration para-
meters. The current configuration may be saved in
a non-volatile memory by pressing on the SToRE
key then on the CONFIG key.
Factory default parameters:
AUTo
Frequency
Bias
Equivalent circuit
Impedance range
Display
Memory A
Memory B
Mains frequency setting
The HM8018 includes a dual slope A/D converter
which needs to be set according to the mains
frequency in order to obtain a good frequency
rejection.
Press on the FREQUENCY key
the message 50.-60 appears.
Then press on the -A key
on the AUTo key
for a 60 Hz mains. The decimal
point is placed on the right position of the active
frequency.
Press on the SToRE key to save the frequency in
a non-volatile memory, or any other key to exit
without saving.
at power on, until the
oN
1kHz
oFF
AUTo
AUTo
L/C/R (AUTo)
0.0
1.0
at power on until
for a 50 Hz mains, or
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