Devices Used to Connect Circuits
- In the laboratory we define Connection
Devices as the wires used to connect
circuit elements such as resistors, sources and measuring
- Now there are three basic types of connection
devices in use within the First Year Laboratory, these
are listed below:
1. 3mm Cable:
- This type of cable derives it's name from the
size of the plug it has at each end.
- When 3mm cable is used we have the following
- We require two 3mm
cables to connect sources and measuringdevices to
the circuit (one positive and one negative).
- The 3mm cables can be connected directly
to the DMM
and D.C. Power
Supply as both of these
devices hav 3mm plug
inputs and outputs respectively.
- The 3mm
cables cannot be connected directly to the CRO Input
Generator Output because the
inputs of these devices use of a BNC
connection. For this reason we need a 3mm
to BNC adaptor. This adaptor
is shown below on the right of the 3mm
- When we look
at the diagram above we see that the adaptor has two
terminals. The terminal marked with the (-)
is the Negative Terminal an should always be connected to
the GROUND node of the circuit we are taking readings
- Now the other terminal marked with (+)
is the Positive Terminal and should be connected to the
node at which we wish to find the voltage.
- Finally the BNC connector at the bottom of the
adaptor needs to be connected to the CRO input itself.
- Coaxial cable is the most convenient connection
device for taking readings using a CRO and
providing an A.C. source using the Function Generator.
- As the diagram below shows, one end of the cable
has a BNC connector which fits directly onto the input of
or Function Generator
- While the other end splits into both a Red
Positive and Black Negative cable.
- The above cable due to it's thickness contains a
great deal of Stray Capacitance, this in turn causes the
distortion of extremely small signals.
|Things to Remember About Coaxial Cable
- Always connect
the Negative cable (Black) to the GROUND point of
- This type of cable is not useful for very
small signals (around 1mV).
- The most convenient of the above types of
cable as we only require one cable per BNC
connection rather than the two required by the 3mm
- Coaxial Cable cannot be used with D.C Power Sources
or the DMM.
3. X10 Probe:
- Here we have the most sophisticated of the
connection devices, it is really only used when we
require very accurate measurements in Digital Systems or
Small Signal Electronics.
- It is only used to make measurements in
conjunction with a CRO.
- In the diagram below we see that the CLIP
on the side of the Probe must be connected to the GROUND
Node of the Circuit.
- The TIP
of the Probe should be attached to the part of the
circuit at which we wish to make a measurement.
- Finally the Probe can be used to amplify the
signal it is being used to measure by a factor of ten.
This is done using the switch on the side of the Probe.
to Main Menu
Page maintained by EIE WebMistress
Revised: Friday, 17 July 1998