Operating Instructions Of The Frequency Counter; A Basic Setting; B Measurements Using The Frequency Counter; Freq - Conrad MXC-2800 Bedienungsanleitung

Operating Instructions for the
Frequency Counter

A Basic setting

1.Connect the mains connection socket to the mains power line. Make sure that
the connectors are correctly seated. Next, connect the ground contact plug to
a protectively grounded contact socket.
Important !
There should be no breaks in the protective conductor connec-
tion, either within the device or in the mains cable. A break consti-
tutes a potentially lethal hazard.
2. Press the mains ON/OFF switch (4).
3. If you wish to connect signal sources from BNC sockets to the function gene-
rator, you should normally use a coaxial cable for connection. Such cables are
shielded, i.e. the inner signal-carrying core is shielded against external noise
signals by a braid of copper or tin-coated copper wires. This shield is connec-
ted to the ground of the feed-in source (or the counter).
If signals across components or sub-assemblies are to measured by circuits,
use coaxial cable fitted with a BNC socket at one end and open at the other
end. The open ends are fitted with crocodile clips.
Important !
The ground connections of the counter, the BNC sockets
(1a,b,c,d) and the RS-232 interface connector are connected
directly to the protective ground conductor of the mains connec-
tion socket or the connected mains cable. Make sure that the cir-
cuits in which you are making your measurements decoupled
from the mains via an isolation transformer. Never connect BNC
inputs or outputs directly to the mains, with chassis carrying live
voltages, or circuits operated without transformers (decoupling of
input and output). Potentially lethal hazard!
Please observe the max. input. Never connect voltages greater
than 3 Vpp to channels A, B and C. Ahead of each measurement,
check all BNC sockets for damage or shorting.
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If source resistance or line capacitance of a direct line connection between the mea-
surement object and the frequency counter, in particular at high frequencies, are
unknown, use a 1:10 scanning head of low capacitance for inputs A and B. However,
for channel C do not use a scanning head, because the relatively high impedance
may falsify the measurement value.
One option of keeping measurement error to a minimum in coaxial cables, is to use a
specific insulation resistance (terminator). The impedance of this resistance, which is
connected directly to the frequency counter, must match the impedance of the signal
source or cable.
Example: Output resistance of a frequency generator = 50 ohms,
line resistance of the coaxial cable used = 50 ohms,
==> Resistance value of the specific insulation resistance = 50 ohms
Important !
Make sure that the circuit in which you are making your measure-
ments is decoupled from the mains via an isolation transformer.
Never connect BNC inputs or outputs directly to the mains, to
chassis carrying live voltages, or circuits operated without trans-
formers (decoupling of input and output). Contact is a potentially
lethal hazard!
Never exceed the max. inputs, which may result in damage to the
device and a potentially lethal hazard to the user.

B Measurements using the frequency counter

General Notes on Safety
• Take special care when handling voltages greater than 25 V AC or 35 V DC.
Even direct contact with electric conductors at these voltages can cause a
potentially lethal electric shock.
• Ahead of each measurement, check the frequency counter and your measure-
ment leads (scanning heads, BNC sockets, and cables) and your mains cable
for damage.
• To prevent an electric shock, please make sure that you do not touch, even
indirectly, scanning head probes or crocodile clips in open BNC lines, as well as
the connecting (measuring) points you are measuring.
B1 Frequency measurement A or B or C
The frequency of a measurement signal is the reciprocal value of the period duration
f = 1/T. To measure frequency, connect a coaxial cable to the input of the counter
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