Instrumentation (Page 6)

Test and Measurement Technologies

This is a 20 Tera Ohm Insulation Tester I made around 20 Years Back. It had even Polarization Index for Transformer Insulation. It generated 1000V DC Regulated Voltage and the pA leakage Current was Measured. See more here Insulation tester or Tera ohm meter.

Insulation Tester

A regulated, low ripple, high voltage of very low current capability is applied by instrument on a DUT (device under test). The leakage current in nA or pA (picoamps, nanoamps) is measured and readout, The Innovation i did was to measure the current in Vref and not Vin of ICL7107, this made the 1/x computation.

Also using the ICL7650 Chopper Stabilized amplifier must be done as shown in data sheets with grounded guard rings. pA will leak on the PCB itself if layout is not done keeping this in mind.

This was a Beta Hfe and Vce Measuring Instrument used in Incoming Inspection of Power Transistors made by me 16 years back.

Transistor Beta Tester

Custom Built Test Instruments

I designed and built many custom “engineered” Test Instruments. They were not prefect, as only one or two were fabricated. That means it will be costly to produce such instruments. It is just like tooling, you have to make some numbers to recover costs, or price it very high to compensate for the wastages and iterations.

When making custom equipment, you have to have an extended service agreement like 5 years. Also request a minimum order of at least 5. Make your R&D and Inventory Modular. That way it is profitable and some money available for reinvestment on instruments and Equipment for calibration and quality.

Here are some Test and measurement notes. These ideas come from practical experience. But the jots are not in any order but are quite important.

Instrumentation and Automation

Scope 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.
  • 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”.
  • 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.

DMM Notes

  • 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 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 photo sensors.
  • 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 impedance ranges.
  • 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 When you do not have a scope you can build one for the PC.
  • Polarity and Zero Cross indicators┬átell you to swap the leads. Use a comparator or opamp to build it.

New and Used Electronic Test Equipment from Tucker Electronics

  • New Test Equipment
  • Refurbished Test Equipment
  • Used Test Equipment

Tucker Electronics continues to offer New and Refurbished Oscilloscopes, Analyzers, Meters, Counters and Power Supplies from quality manufacturers.

Here is a page i scanned from an old 1986 Tucker Catalog. Standards and Equipments .

From Electronic Catalogs

Tucker maintains a large inventory of both new and re-manufactured instruments so you can get what you need fast. Many quality test and measurement instruments from manufacturers such as Agilent, Tektronix, Rohde and Schwarz, Fluke, and California Instruments.

Test Tools are needed for Troubleshooting and Repairing Electronic Gadgets, Equipment, Electrical Panels and Machines. Precision Instruments are required for calibration of field and machine control electronics. These are also required by the R&D engineer for design and development of new products and trying out new concepts.

Test and Measurement

Test Measurement and Test jigs - delabs

In Production testing, Production Engineering, Quality Assurance QA-QC etc. You need to build Test Jigs, Configure Automated Testing depending on the size of project or budget allocated; yet it has to be made flexible, scalable and modular. These require instruments or blocks that can be adapted and reconfigured or even interface with a computing network for automated testing, reporting and analysis.

Special Electronics come with every tool or gadget these days, A Slide calipers has a LCD display, Digital Readouts on mechanical instruments can help measure even sub-microns easily. Analytical and Chemical Instrumentation is another specialized niche. Then we have medical instrumentation which is more demanding in quality and requires sensors that are small, very sensitive and safe.

Instrumentation goes into all these and beyond. The day we find water on mars, It is only because of a precision instrument at the helm of things.

These are basic measuring circuits you can build for your home lab. I have documented a lab DMM i had built for my use many years ago. the circuits may have errors, build it only if you understand.

For the past 30 years, National Instruments has been a technology pioneer and leader in virtual instrumentation – a revolutionary concept that has changed the way engineers and scientists in industry, government, and academia approach measurement and automation.

LabVIEW, Data Acquisition, Modular Instruments, PXI, Programmable Automation Controllers.
Here is a page from an old NI Catalog. RS-232 Tutorial of NI. drag-drop image to read.

National Instruments – Test and Measurement

One which is useful for beginners is the LabVIEW Student Edition – LabVIEW easily connects to any device be it hardware or outside applications like Microsoft Excel. You can depend on this seamless development experience as you write your program.

Fluke test tools, answering your electronic, electrical, predictive maintenance and biomedical needs.

Fluke – Education and Training

  • Intrinsically Safe Application Notes
  • Insulation Testers
  • Standards and References
  • Fluke Technical Papers
  • Earthground

Fluke Biomedical Instruments and Equipment

Shown below is ESA620 an Electrical Safety Analyzer that performs all primary safety tests, including mains voltage, protective earth resistance, insulation resistance, device current, earth, chassis, and patient leakages…..

Fluke Biomedical Instruments and Equipment