Test and Measurement Design
Analog Circuits are the core in any
instrument design, Even in a
Instrument with Digital or uC control.
The Interface to the Real World
parameters is Analog. High Speed
Analog and High Energy Measurements
are the challenging areas.
T&M and Process Control
Instrumentation have many things in
common; but the conditions in which a
Industrial Instrument works, may be
Industrial Instruments are used both
in Clean-Cool Control Rooms and also
in a corrosive, humid, hot and
vibrating industrial environment. Even
high levels of Static, Magnetic
influences in conjunction with spikes
and brown outs can be expected.
Test and Measurement instruments are
of two types, by way of its usage;
Portable and Benchtop. Portable
Instruments will consume low power,
insulated and rugged. The Product
Safety features are more stringent as
they are HandHeld or slung over the
shoulder. Some features and specs are
sacrificed. The Benchtop version has
more front panel space and can
interface with other instruments or
systems. More accuracy and features
can be accommodated in this.
Instrumentation Notes -
- If the waveform on the scope
droops then you may need to use a
10X attenuating probe or mode.
this attenuator is at the tip of
the probe hence better measurement
possible, also very high frequency
signals may be best transmitted
over a 50 ohm impedance matched
line to the Oscilloscope.
The History of Oscilloscope, Learn
more about Oscilloscope from the
Innovator of the Scope as a
Measuring Instrument here is XYZs
Braun - In 1897 he built the
technology is to this day used by
most television sets and computer
monitors. The CRT is still called
the "Braun tube".
- Test a NPN transistor, DMM in
200K range. emitter negative
probe, collector positive probe,
it should show open. while still
holding that way press wet finger
on base and collector, it may show
some reading, then it is ok. for
PNP swap probes polarity and do
the same thing. the wet finger
when pressed applies a base
current in uA.
a Mosfet - Transistor
Tester - Basic
of Semiconductor Devices
- The most common reason of DMM
failure is when a person tries to
measure 230V AC with a DMM in
current or ohms mode, with the
probes in the wrong sockets. Use
external attenuators and shunts.
- A DMM in diode mode or
resistance mode can be used to
test IR diodes, take it under 100W
lamp and measure, cover the IR
diode and measure you will see a
response in proper polarity.
- If you put the DMM in 2V mode
and measure the voltage across a
ordinary LED near a 40W lamp you
will see around 200mV. Turn off
40W lamp the mV will fall near 0.
Even metal-can transistors with
their top ground away will become
- When you measure low voltages or
high resistance like 1M with a DMM
your body must not be in contact
with the probe tips. Body
resistance is low in comparison so
error in reading or loading of mV
from sensor, in sensitive and high
- Do not use an oscilloscope to
measure 230V directly, use a
transformer, differential probe or
- An oscilloscope 1M probe or a
DMM 10M impedance can load
circuits with nano-pico amps of
- Red socket and probe for
positive and black socket and
probe for negative
- Is it oscillating ?.... We
cannot say, it could also be DC,
you need to see if a Clock is
present. use a signal tracer or a
DMM freq mode, or AC measurement.
or build this solorb.com-elect-logicprobe.
you do not have a scope you can
build one for the PC.
- Polarity and Zero Cross, a
polarity indicator, which will
tell you to swap the leads.Zero