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The one above was also made at TMPL, it is a Psophometer which was a true RMS auto-ranging AC dB level meter with weighted filters. The weighted filter has to resemble the audio response curve of the ear. With a built in signal generator in dB settings it becomes a Transmission Measuring Set. This was in the eighties, it is similar to this Transmission Measuring Set from Aplab, this was the only relevant link i got. I also remember that aplab also had submitted a sample of a bigger unit then. Then some nice European units also were being evaluated by the buyer.

Related Resources

• Marconi TF2333 MF transmission measuring set
• Noise- Developer Zone - National Instruments
• Heavy Duty Transmission Line Test Sets
• Enhanced Audio Test Set

These are Electro Mechanical Points which i noted from my past experience, in my Amps-n-Volts Newsletter.

• The tracks or components on a PCB should not be near the mounting holes, the tracks may form electrical connections with the cabinet earth if they touch the pillar, washer or nut-bolt.
• When you tighten the screws-nuts-bolt limit torque by feeling or with torque limit screwdrivers, or thread will slip or PCB-Cabinet break, or CRT-Glass-Plastic will crack-shatter.
• After assembly and testing is over on a board, do not drill-file it, it should have been done before. Else components crack or tracks break or small metal pieces will form shorts.
• The Mechanical and electro-mechanical must be streamlined before production, for example when fitting the board the screwdriver may slip and break a zener. The product should be engineered in such a way that it fits easily and the testing and quality checks need not be repeated.
• Some mechanical failures may not be visible but may show up as a field failure after even 3 months. this will make you lose further orders and ruin the reputation. Hence design engineering is vital.
• Sparking at the high voltage mains supply power contacts like a plug can cause electronic gadgets to fail. When you drive nails into walls ensure that that part of the wall is free of mains, telephone or any wiring.
• Some pcbs can have hairline cuts or hairline shorts which will make troubleshooting difficult.
• Never ‘put or remove’ ICs, cards or plug-in modules when the power to that system is on, power off system wait for some time for caps to discharge, then insert ICs or cards, applies to PCs too, USB and Firewire ports are exceptions as they are hotplug, anyway even in this, take a bit of care as some peripherals may cause some problems.
• Teflon tape can be used to make leak proof pneumatic or hydraulic connections if junctions are leaking.

Psophometer - Wikipedia, the free encyclopedia. I learnt some basic instrumentation when i worked on above Instrument, Mr. Ravi Rao the Manager in Trans Marketing Pvt. Ltd. gave that opportunity. TMPL as it was known decades back was in Service and Sales of many Brands like Racal Dana, Genrad, Data I/O and Electronic Production Machinery.

Related Resources

• Digital Psophometer Model 1072
• Automatic Loss Measurement
• Weighting filter
• ‘A’ Weighting Filter For Audio Measurements
• Programmable Universal Filter C-Message Weighting
  

This is a Multi Zone Temperature Control panel used in Plastic Extrusion Moulding. We made many of these and it helped us learn cable management techniques. The panel is a standard way it was built and some of the merits were the selection of panel components and wiring expertise.

20 Turn Bourns	Single Turn Wire-Wound	Single Turn Film	10 turn Spectrol
Precision, Linear Temperature Stability Instrumentation Many Operations Panel Control Encoders	Panel Control 1 Watt Wire Wound Temperature Stable Blind Timer Thermostat	Panel Control Volume Control Motor Control Low Cost Low Power Log and Linear	Precision, Linear Temperature Stability Instrumentation Many Operations Panel Control Encoders
Multi-Turn Trimpot	Multi-Turn Trimpot	Anvi Preset	Single Turn Preset
Calibration Side Adjust Tweak Temperature Stable Many Operations Fine Control, Linear	Calibration Side Adjust Tweak Top Adjust Tweak Fine Control, Linear Many Operations	Single Turn Cermet Small Footprint Calibration Low Cost	Dust free Many operations Horizontal Mount Vertical Mount too Calibration

Read More-

• Potentiometers- Beginners’ Guide to Pots
• Variable Resistors
• Basics of Resistors

Standards

CBEMA - Computer Business Equipment Manufacturer’s Association
adopted curve IEEE Standard 446 (orange book) curve.

Recommended Practice for Emergency and Standby power systems for Industrial and Commercial Application.”

• Wave form Sine wave THD (total harmonic distortion) maximum 5%.
• 3 Phase system phase imbalance of voltage 3% - 6%.
• Frequency stability 60 (50 Hz in India) +/- 0.5Hz.
• Output Voltage +6% Max. -13% Min. from Nominal Value.
• Voltage can fall to 0V but should recover in 0.5 Cycles.
• On turn on Voltage should reach steady state within two seconds.
• Upto 200% over Nominal Voltage should be tolerated for 100uS. ( Transients, spikes and Inductive Kickbacks come in this)
• Upto 30% over Nominal Voltage should be tolerated for 0.5S.

ANSI - American National Standards Institute

“Standard Voltage Ratings for Electrical power systems & Equipment”

• Steady State Variations +/- 5% of Nominal Voltage. T
• Three Phase Voltage Imbalance 5% Max..
• Standard Frequency 60Hz.

Glossary

• Frequency 60Hz Hz is Hertz.
• One Cycle = 20mS (milliseconds) one full sine wave.
• In India Standard Frequency is 50Hz.
• Max - Maximum
• Min - Minimum
• uS - micro seconds, S - seconds.

Cause of Transients

1. Switching Loads Simultaneously (inductive loads).
2. Power factor correction capacitors and devices.
3. Lightning strikes (enhanced by earth faults).
4. Line Inductance (inductive kickback, resonance).
5. DC and AC Drives for Motors.
6. Rectifiers with large filters and stray inductance.

Extra Reading

• Power Standards Lab
• CBEMA Guideline
• ITI (CBEMA) Curve PDF

UPS Inverter

• Power Inverters DC-AC
• Keep your networking gear going 24/7
• Various Schematics and Diagrams
• A Mos-Fet Power Inverter
• Circuit makes simple high-voltage inverter
• Electronic Transformer - Inverter Transformer
• 500 WATT DC-AC by SM0VPO
• 12 Volt DC to 120 Volt AC Inverter
• 110VAC Inverter for Automobile
• A High-Powered Power Backup Inverter
• DC to AC Circuits and Inverter Circuits
• Power electronics - choppers, inverters, motor drives

This is a Regulated 0-30 V DC Power Supply manufactured by me in small numbers, 0-30V 5A and 5V -5A. It had a Switching Preregulator. This keeps the Vce across Transistor Bank at the Back of Instrument, at the lowest possible level, in order to keep them Cool. When Vce and Ic both are more in a Power transistor it will get heated more, then the efficiency of power supply is low.

The Output had both Constant Current Control and Constant Voltage Control. The CC control is also a Short circuit protection. The Output was protected from outside voltages damaging output circuits even when equipment is switched off. The back panel is a finned anodized black aluminum heat sink with many transistors.

I looked for the circuits to scan them, i could not find it. I made-n-sold quite a few of them years ago. All of them work well even today as i over-rated most components. The cabinet was Steel for EMI-RFI Immunity, it was painted with Stipple Matt Powder Coating, the Cabinet maker had just learnt to give such a finish to his boxes.

Read more

• Electronics Cooling
• Heat sinks for transistors
• ESP - Heatsink design and transistor mounting
• Technical Papers
• Heat sink - Wikipedia, the free encyclopedia
• Power Supply Adjustable 30
• 3-30 V/2.5 A Stabilized power supply
• Small Variable power Supply
• Power Supplies
• The educational encyclopedia, Supplies
• Build A 10 Amp 13.8 Volt Power Supply
• Bench Top Power Supply, 30V - 10amp
• 40A Power Supply Unit

Study these applications at IRF Applications and ST Application Segments. Some pages related to power supplies below. Power Design Section

• Coils and Transformers for SMPS
• Mains Transformers Types
• Good Voltage Regulators
• Transformer Connections.
• Dual Power Supply
• 5V -1A Power Supply using LM2575
• Digital 5V Power Supply using L296
• Isolated dual power supply