Electronic Engineering Schematics
Test and Measurement Instruments
Instruments designed and built by delabs.
These are Instruments that Jack built. Here read Jack as me,
delabs. Some were hand made, some in the form of workflow of a
small firm with professional equipment. Some made in
quantities, other a couple or more for R&D.
Test and Measurement is all about Measurement or Metrics.
Without this, every other part of electronics becomes like
Reverse Bias Leakage Tester
Relationship between Instrumentation and Automation
In Test and Measurement and Industrial Process Control a
common factor is instrumentation. The measuring aspect is
common to both. T&M instruments are used in Testing,
Research,Automated Testing, Troubleshooting and Servicing.
An early T&M company was the ... Wandel
and Goltermann - Communication Instruments
Process control Instruments are used in Production Lines made of
Machines in a Factory. It could be Counters and Timers used for
Textile or Steel Industry. It can also be Temperature and
Pressure Controllers used in Oil Refining or Food Processing.
So you see a difference. We have handheld Test Instruments
like DMM and Scope and We have Handheld Instruments for Gas
Monitoring or Humidity too. In automated testings we have rack
mount test instruments. In Control panels we have Rail Mount
carrying DIN standard Instruments.
to Build Lux Meter - ELM
Points in Instrumentation
- On-Off controls or level trip relays can oscillate if
hysteresis dead band is very small or absent.
- Hysteresis is like on at 300 off at 304 like in heaters or
air conditioners. If you on-off at sharp 300 there is a
chatter or oscillation. This is called dead-band in
temperature control. In above example 304-300=4 is the
- LF356, TLO71 and CA3140 are FET input Op-Amps, the bias is
in pA, The caps for sample hold with these opamps are low
leakage ones.10uF tantalum for long time, low resolution
data. Long hold times with 12 bit data (analog) use 1uF
plastic multilayer and clean-IPA + coat PCB with epoxy.
- Design the product in such a way that neither the pot
terminals or pot switch is used for mains voltage, instead
use the pot switch or variable resistance for signaling and
the mains can be switched with Relay or Thyristor.
- If you need a 10.00K resistor 0.1% and you only have 1% in
the market, you can trim lower values to higher values by
removing the paint of the resistor and scratching the black
metal film till you get the desired value. (this is only for
testing or prototype development, R&D, not for
- 7107 and 7135 of Intersil can be tested in-circuit, check
Vref for 100mV or 1V reference, then short Vin and Vref the
reading should be 1000 counts for 7107 and 10000 counts for
7135. ground plane should be good, no ground loops, PCB only
glass epoxy and low leakage caps to be used, then reading
will be stable, use some coating on soldered PCB.
- An electrically Noisy environment can be simulated with a
hair drier, or hot air blower. Another way Looping the NC
(normally closed) contacts of a 230V Electrical
Contacter-Relay can make it oscillate, this makes a lot of
Sound and more important is the Electrical noise rich in
EMI-RFI. This helps basic testing of timers, counters, uP,
uC and embedded systems as they may malfunction in noisy
- A Single Pole 12V 100mA relay in a feedback loop, with its
contacts, can make a Electrical or Electromechanical
Oscillator. This can test your ground loops and digital
circuit decoupling caps. It simulates power spikes which may
reset some counters.
- When a Machine with many stages or even an entire
production line has to be automated, a PLC system is easiest
to configure. It has digital inputs for limit switches and
proximity sensors, it has analog inputs for any other
parameter sensor. The PLC output modules can drive
Electrical Contactor circuits with 230V Signal or 4-20 mA
for an AC drive. The tacho-generator voltage feedback or
pulses feedback from a motor can be fed to PLC inputs too.
- Automation is used to enhance the quality and quantity of
the product, also where there is danger to operators or
workers. This moves the worker up, into the maintenance and
management of materials, machines and systems.
- Industrial Automation is essential to enhance the
manufacturing worker to deliver consistent, repeatable and
timely delivery of products. Absence of automation makes
quality and deliveries unpredictable and stresses worker on
monotonous jobs. When the worker is creatively employed with
his machine on automation, it is the best scenario.
Test and Measurement
30th Aug 2020