Electronic Engineering Schematics
Instrumentation and Measurement Circuits
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.
Reverse Bias Leakage Tester
T&M and Process Control Instrumentation have many things in
common; but the conditions in which a Industrial Instrument
works, may be very unfriendly.
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.
in Test Measurement
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
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 of Oscilloscopes.
- Karl Ferdinand Braun - In 1897 he built the first
cathode-ray tube...oscilloscope. CRT 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.
- 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
- 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 attenuator.
- An oscilloscope 1M probe or a DMM 10M impedance can load
circuits with nano-pico amps of bias.
- 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 a
logicprobe. When 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 Crossing Detectors,
More Designs in PDF
20th Mar 2020